After checking the ignition system, ensure the ignition timing is in accordance
with the manufacturers' recommendations.
Two suitable methods are shown:
a. Static Ignition Timing
b. Stroboscopic Timing
Static Ignition Timing
Rotate the engine until No. 1 piston is just before TDC on the
compression stroke. At this point, the rotor arm should be pointing to the
distributor cap segment connected to No. 1 spark plug. The contact breaker
points should be just at the point of opening in the direction of rotation. THis
can be verified by connecting a voltmeter between the distributor LT terminal
and a good earth. At the precise moment the contacts open, the voltmeter will
register battery voltage. Should the ignition timing be incorrect, centralize
the micrometer adjuster (if fitted), slacken the distributor clamp bolt and
position the distributor to the point of contacts about to open and re-tighten
It must be remembered an incorrect contact gap can affect ignition
timing. The contacts must be set and maintained at 0.35-0.40 mm
The ignition timing is now set with sufficient accuracy to be able to
start and run the engine. Final adjustment may be carried out using the
stroboscopic timing light and micrometer adjustment.
Connect the strobe HT pick-up into No.1 plug lead and disconnect the
distributor vacuum pipe. In the case of a separate strobe, battery supply will
also be required.
Start and run the engine at the manufacturers' specified idling
speed. Direct the strobe light on the timing marks and check the degrees of
advance against the recommended figures.
The strobe light can also be used to check that the centrifugal and
vacuum advance mechanisms are operating, but in order to do this, the figures
obtained must be compared to those specified to the particular vehicle.
Fused Circuit Short
This is not uncommon- every time you put in a new fuse, it blows before you have
a chance to figure out where the problem is... Next time, replace the fuse with
an old turn signal flasher (one that works). Attach the two leads of the turn
signal flasher to the contacts where the fuse normally sits; the flasher will
click on and off, which gives you a chance to sort out the problem without going
through a box of fuses or burning the harness.
Distributor Breaker Points
Function: The function of the points is to make and break the electrical circuit
to the coil. Each time the points open, the circuit is broken, causing the
magnetic field around the
ignition coil to collapse. When this field collapses, a high voltage spark is
created that fires the spark plug. The points must open sufficiently to break
the circuit and minimize arcing. The points must remain closed long enough for
the magnetic field to regenerate before the next spark plug is fired. The
distance the points open is called "gap", and the amount of time they
remain closed is called "dwell'. On a four-cylinder engine operating at
3,500 RPM, the points open and close 7,000 times per minute.
Problem Areas: Each time the points open, a very small amount of
metal is transferred from one side of the points to the other. This transfer is
uneven, and in effect closes the point gap. The second problem area is the fiber
block that rides on the distributor cam and opens the points. This fiber block
not only seats itself on newly installed points, but wears on points that have
been in use for long periods of time. The combination of wear and metal transfer
will eventually close the points completely, and the engine will no longer run.
Symptoms: As the gap begins to close beyond some rather broad limits,
the engine will start to misfire under hard acceleration. As the gap closes even
further, the engine will start to miss at normal road speeds. Further closing of
the gap will result in an engine that is hard to start and impossible to make
idle properly. These symptoms are very similar to those of fuel starvation
caused by a faulty fuel pump, plugged fuel line or filter, or dirty carburetor.
Conclusion: Before taking the fuel pump apart or tearing into the
carburetors - both messy jobs - check the point gap.
Additional Information: During the past summer, I assisted at least
nine different owners that thought they had fuel starvation problems, when in
reality they had points that had closed beyond their limits. It is a good idea
to carry a spare set of points in the car, as a badly burned set of points are
nearly impossible to set.
Checking Your Distributor
Next time you pop the cap on your Lucas distributor, take a moment to put a few
drops of oil on the screw under the rotor there are holes under the screw and
the oil will lubricate the cam bearing. While you're at it, lubricate the
advance mechanism and the breaker point pivot. Use light engine oil. If you are
out of grease, a drop on the breaker cam lobes won't hurt.
I was converting my older British car over from positive to negative ground when
I came across the question of coil polarity. I discovered coil polarity is very
much misunderstood. In researching it, I was very confused until I found out
there are two definitions of coil polarity. I talked to three or four
knowledgeable people on the subject and read several technical books and
articles. Everything made sense in itself but didn't jive together until I found
out they were talking apples and oranges.
Definition #l Coil Polarity (In relation to battery)
The polarity of
the coil should match that of the battery by connecting it so (+) goes to (+)
and (-) connects to (-). But don't worry about which way you install the battery
(positive or negative ground) or which way you install the coil (regardless of
coil markings) it will automatically adjust itself. The coil will work
efficiently and put out the same voltage either way it is hooked up, but the
spark plugs are more sensitive when it comes to polarity, hence our second and
more important definition.
Definition #2 Coil Polarity (In relation to spark plugs)
Coil polarity should be such so as to provide negative polarity to
the spark plugs center electrode.
It has been found that it takes approximately 15% less voltage to
form an arc at the plugs, if the hotter center electrode is negative, and the
cooler (by comparison) ground electrode is positive. The center electrode is
hotter since heat transfer from the tip must make its way through the porcelain
insulator past the sealing gaskets to the shell block and then to the water
If your center electrode is positive, your car will probably still
run fine until, with its 15% handicap, it exceeds the coil output. If you live
where temperatures dip down to 0° you may not get your car started. Driving
with a full load and accelerating hard up a hill may cause an ignition miss. If
your ignition system is well worn to where you have various voltage losses, you
could get a miss.
Correct coil polarity won't eliminate these problems, just put them
off by 15%.
If your coil has - & + markings by the primary terminals, you
will be pretty safe by hooking it up by those marks, but test it for correct
polarity anyway, using one of the tests listed further on. If your coil has CB
& SW or BAT & DIST markings, there is no way of telling if the coil was
marked in relation to a positive or negative ground car, and the only sure way
to tell if the coil is installed right is to test it out.
You test for
correct polarity by hooking up a voltmeter with the negative lead to the plug
terminal (which should be of negative polarity) and the positive lead to the
block (which should be of positive polarity). Set the meter on the highest volt
range. These connections remain the same whether you have a positive ground or
negative ground electrical system. The secondary winding's polarity which we are
testing is determined by the combined hookup of the battery and primary
windings, so it may or may not match the battery's ground.
Cranking the engine over (you don't have to start it) should show an
upward swing of the voltmeter needle (don't be concerned with taking a reading).
If the needle swings down off the scale, your coil is hooked up wrong. To
correct, reverse coil primary leads. Do not worry about the coil markings (refer
to definition #1).
If you don't have a voltmeter, test by removing a plug wire from a
plug and hold a plain lead pencil point in the path of the arc. A flair (hard to
see) towards the plug shows correct polarity while a flair towards the coil
shows reversed polarity.
Engine ground straps are essential, as they provide the ground connection for
the starter motor, which typically draws 200-300 amperes. Should a ground strap
be badly frayed, corroded, or otherwise unable to support this current, the
starter motor will not be able to function efficiently. In extreme cases, the
current will be carried by whatever else is providing a current path between the
body of the car and the engine - usually the choke cable, which will become red
hot, and may even burn through.
Alternator Terminal Conversion
Many British cars are wired
for 5-terminal alternators. As the 5-terminal alternators are now obsolete,
3-terminal alternators may be supplied. These wiring instructions, provided by
Lucas, outline the conversion procedure. To wire a 3-terminal Lucas alternator
in place of the now obsolete 5-terminal alternator, use plug kit #540-280 and
proceed as follows:
·Cut off wiring terminal plugs from alternator wiring
·Remove and discard link wire (see illustration below)
·Remove wiring harness tape approximately 1 inch
·Slide small insulator over remaining IND wire (brown/
yellow), and solder to the small terminal
·Slide larger insulator over positive lead wire (brown/white), and
solder to the larger terminal
·Separately tape back onto harness, the brown and black wires not
used as they are no longer required
·Connect the small brown/yellow IND wire to the small
terminal on the alternator
·Connect the large brown/white positive lead to either of the two
large terminals on the alternator
·Re-connect the battery
Audible Directional Flasher
Here's a tech tip for those of us whose hearing is not what it used to be when
we were younger, or those of us who are younger and just can't hear the
directional flasher or see the flasher indicator light, especially with a top
down in daylight. Since the time delay, even when set at max, does not give a
long flashing interval, it is useful to know when it has stopped, in order to
make turning intentions more obvious.
I purchased a Radio Shack catalog 12-volt mini buzzer (no. 273-055),
for just under $3.00. Just mount it anywhere it is convenient under the dash and
on the driver's side. This is most easily done with double-backed foam mounting
tape (3M). Then run the black wire through the firewall and connect it to the
center flasher terminal. Ground the red wire under the dash. This buzzer emits a
sound that is not the most pleasant, so take one turn of black vinyl electrical
tape around it to cover the sound louvers and mute the buzz.
Lucas Wiring: A Simplified Solution
Lucas wiring systems as used
on virtually all British cars since the 1930s are a source of frustration and
bewilderment to a great many sports car enthusiasts. In fact, Lucas wiring is
clearly engineered around a standardized color code and cable size formula. This
system is used on all British sports cars and once understood, is very simple.
The following detailed explanation has been excerpted from a Lucas
technical manual which dates from the mid-1950s. The professional mechanic or
die-hard enthusiast may wish to clip out this article for future reference.
After all, this information could be invaluable in sorting out the "Manumatic"
gearbox wiring of your 1957 Borgward Isabella estate wagon!
With few exceptions, the electrical system of a motor vehicle can be
considered as a series of simple circuits, each consisting of the component, its
switch and three wires - feed, switch wire and return. On earth return systems,
the return circuit is provided by the frame of the vehicle. Although in the case
of components insulated from the chassis, an earthing lead is also necessary.
Some variations are to be found, such as fuses, two-way switching and so, but
the principle of feed wire, switch wire and return remains, and it is upon this
principle that the Lucas color scheme is based. The insulation on feed wires
carry a main color only, switch wires have the main color of feed with a colored
tracer running the length of the wire, while return earthing leads are black.
Where components are switched or controlled in the earthed side, that
is, with the switch wire on the return side of the unit instead of on the feed
side, this is normally indicated by the use of a black tracer.
Main colors, of which there are seven, are allocated to the circuits
as shown below. The practice of feeding certain of the accessories through the
ignition switch and auxiliary lighting circuits through the side and tail lamp
switch is recommended, so that the side and tail lamp switch and ignition switch
wires become feeds to other circuits or, in effect, master switch wires.
BROWN Battery circuit. From battery or starter switch to ammeter or
control box and (with compensated voltage control) feeding lighting and ignition
switches (and radio, when fitted) from control box terminal. Also, from starter
switch to electric clock, inspection sockets and battery auxiliaries fuse (from
which are fed electric horns, cigar lighter, interior lights, etc.).
YELLOW Generator circuit. From generator terminal to corresponding
control box terminal and to ignition warning light.
WHITE Ignition circuit and all requirements essential when ignition
is switched on but which do not require fusing, e.g., electric fuel pump,
starter solenoid switch, etc.
GREEN Auxiliary circuits fed through ignition switch and protected by
the ignition auxiliaries fuse, e.g., stop lamp, fuel gauge, direction
indicators, windscreen wipers, etc.
BLUE Headlamp circuits. Fed through terminal on lighting switch.
RED Side and tail lamp circuits. Fed from terminal on lighting
switch. Included in these circuits are fog lamps, panel lights and other lamps
required only when the side lamps are in use.
BLACK Earth circuits. If a component is not internally earthed, a
cable must be taken to a good earthing point on the chassis.
Hopefully, the above information, combined with a proper wiring
diagram for your car, will help turn that multi-colored mass of spaghetti into
an understandable wiring system. Don't get discouraged; Lucas really did make an
effort to use logic in their wiring.
Two basic tools are essential for trouble-shooting electrical problems - a
wiring diagram, and a 12 volt test light. A test light is an inexpensive little
tool that looks like a cross between an ice pick and an electric screwdriver.
Simple to use, it is connected by its clip to a ground. The sharp probe is poked
around the "hot" leads. If the lamp lights, there's power, at least to
that part of the circuit. For example, clip the test light to a bumper bolt or
other good ground and touch the probe to a bulb contact on the "hot"
side - the bulb will light, (so long as the light is "on").
Most lamp problems are conveniently found in the lamp unit itself.
The great majority are caused by bad bulb contacts or corroded grounds. Don't
assume that there are major problems until the non-functioning unit is
completely inspected. Using the wiring diagram, work your way back through the
circuit to the connectors, and from there to the source of power such as the
fuse box or terminal connector. By this method, you should be able to determine
whether an entire circuit or the individual unit is at fault. If the circuit is
dead, track the problem from the fuse box or battery side of that particular
circuit. Proceed through the circuit components one at a time, using the wiring
diagram as a guide. Don't panic! After reading these articles, you should be
well on your way to trouble-shooting Lucas electrics.
Lucas, Prince of Darkness, A Bad Rap?
I have driven my 1960 Bugeye Sprite since 1961, when I bought it new. I'm not
totally convinced that Lucas should be blamed for wet-starting problems. My
Sprite will start and run when even a relatively new piece of Detroit or
Japanese iron won't.
If your car runs fine once it starts, but won't start in the rain or
fog, chances are you have a very easily solved problem. Most likely you have bad
high voltage ignition wires. Replace them. If they are relatively new, take off
your distributor cap with wires and run them through your dishwasher. For your
own safety, I would suggest you do this sometime when your spouse is at the mall
or somewhere else. (A wipe-down won't do as well, since the wires will still
have a film of oil which will attract and hold moisture leading to a short.)
After the wash, rinse and dry cycles, make sure the carbon brush is
still in the cap. Now remove the wires from the cap, clean the distributor and
fire it up. If you have done it well, and you have no other problems like a
defective coil, bad points, or cracked cap, etc., your engine will now start and
run regardless of the weather.
I wash my wires every year or so and my Sprite and Triumph will fire
right up, even after a long winter's nap, regardless of the weather.
Understanding Them and Making Them Work
If you have ever wondered how that simple-looking little three-prong flasher
unit actually performs the task of blinking the turn signal lamps on and off
this no-nonsense explanation should unveil the mystery. Beyond that, it will
provide information of a practical
nature which should be useful in diagnosing and repairing a faulty turn signal
circuit. A 1963 TR4 was the vehicle which launched this project, but the
information herein will readily transfer to other vehicles.
A real flasher unit was carefully dissected to make it reveal its
secrets. It did so, reluctantly. The resistance heater, for example (see ,
Fig. 1), is a wire finer than a human hair. It is so brittle that it will
usually break if an attempt is made to bend it sharply. It cannot be soldered.
It must be spot-welded to the bi-metal strip (10). Since it is the weakest link
in the electrical chain, it is the common source of trouble in the flasher unit.
Even the adventurous do-it-yourselfer will find it much more economical to
replace the flasher than to attempt a repair when it dies.
Fig. 1 gives a general picture of the wiring. It does omit a host of
intermediate connections between the hot battery terminal and terminal #3 of the
flasher. This is of no consequence in explaining how the flasher operates. (Do
not despair. The omitted intermediate connections will be picked up in Fig. 2.)
Note that all of the following components are on the plug-in flasher unit
proper: (1), (2), (3), (9), (10), (11), (12) and (13) of Fig. 1. The small
isometric sketch shows the terminal identification of the plug-in flasher in
Theory of Operation
Assume the driver signals for a left turn by moving the turn signal
switch (8) to the left turn position. An interesting series of events is then
executed. These will be examined one step at a time while referring to Fig. 1.
Step 1. The left front and rear turn indicator lamps (4) and (5) are
"cold"; their filaments have very low electrical resistance. Electrons
immediately rush from the hot battery terminal to terminal #3 of the flasher,
through the resistance heater (9), out of terminal #1 of the flasher, through
the turn signal switch (8), and the cold filaments of the left turn indicator
lamps (4) and (5).
Step 2. The turn indicator lamps (4) and (5) do not immediately come
on, but their filaments do begin to heat up, and during this time period,
current is flowing in the resistance
Step 3. The current in the resistance heater (9) produces heat which
is transferred to the bi-metal strip (10) since the resistance heater (9) is
physically mounted on the bi-metal strip (10). The heat causes the bi-metal
strip (10) to flex or bend by an amount sufficient to close the contacts at
Step 4. Because the contacts at (11) are now closed the resistance
heater (9) is electrically bypassed. Electrons from the hot battery terminal
flow through the heavy wire windings of the electromagnet (12), out through
contacts (11), to terminal #1, through switch (8), and through turn indicator
lamps (4) and (5), turning them on.
Step 5. At this point three things happen simultaneously.
A. The current in the heavy wire windings cause the armature of the
electromagnet (12) to be pulled to the pole of the magnet, closing contacts (13)
which allow the green monitor lamp (15) on the dashboard to come on.
B. The extremely low resistance of the heavy wire windings (12) are
bypassing electrons around the resistance heater (9), allowing the resistance
heater (9) to cool down.
C. The heavy wire windings (12) are furnishing an electron path from
the hot battery terminal to the turn indicator lamps (4) and (5) which therefore
Step 6. The turn indicator lamps (4) and (5) remain on until the
resistance heater (9) on the bi-metal strip (10) cools sufficiently to allow the
bi-metal strip (10) to return to its original position. This takes less than one
Step 7. When the bi-metal strip (10) returns to its original position
the contacts at (11) "open" and two things happen:
A. Electrons can no longer flow through the heavy wire windings (12)
on the electromagnet so the contacts at (13) "open", causing the green
monitor lamp (15) on the dashboard to go off.
B. The electrons from the hot terminal of the battery can get to the
turn indicator lamps only through the resistance heater (9) which, due to its
high resistance at this moment, will not permit sufficient current into the
lamps (4) and (5) to make them stay on. Lamps (4) and (5) go off.
Step 8. Since lamps (4) and (5) are OFF their filaments cool down,
giving them low resistance. This lets heavy current flow in the resistance
heater (9) and the whole sequence is repeated from STEP 1. This cycle goes on
and on until the turn signal switch (8) is returned to the center off position.
Subjected to the scrutiny of careful observation the system is found
to be simple in concept and clever in design.
Trouble-Shooting the System
Time will take its toll in corrosion and rust in all older vehicles.
These culprits not only destroy body panels and structural members, they disrupt
electrical systems in the most insidious manner. If the turn signals are not
operating properly, the circuit may be diagnosed as follows. We are assuming the
battery is at full charge, the ignition switch is on, and the flasher unit is
good. Refer to Fig. 2.
1. Refer to the vehicle wiring diagram to determine if there is a
fuse in the turn signal circuit. If there is, either replace it with a good fuse
or confirm that the original fuse is good. Be absolutely certain that the fuse
terminals and the fuse socket terminals are clean.
2. Inspect the lamps in the turn signal system and insure they are
all good. A bad lamp may cause erratic operation of the flasher unit, since the
operation of the unit depends on the cold and hot resistance of the turn
3. Test the turn signal switch itself.
A. Remove the flasher unit from the socket.
B. Place a jumper wire from terminal #1 to terminal #3 on the socket
C. Turn the ignition switch on.
D. Move the turn signal switch in position to signal for a right
turn. The right hand front and rear turn indicator lamps should come on. They
will not flash, but if they come on and stay on, the switch has passed the right
E. Move the turn signal switch in position to signal for a left turn.
The left hand front and rear turn indicator lamps should come on. They will not
flash, but if they come on and stay on, the switch has passed the left test.
Obviously, if the turn signal switch does not pass both tests, look
for a malfunction in the switch, its contacts, and/or the wiring associated with
4. Remove the jumper wire from the socket and plug the flasher unit
back into the socket.
Assuming the battery is at charge, the fuse is good, the lamps are
good, the flasher unit is good, the ignition switch is ON and the turn signal
switch is good, the turn signal circuit should be operating properly.
Ah! But suppose it does not! Now what?
The next logical place to look for trouble is in the lamp sockets. In
most cases the "ground return" for a lamp is made by the lamp body
simply touching the "ground" side of the lamp socket. You can imagine
that over the years a great deal of dust, dirt and corrosion can build up inside
the lamp sockets. If the sockets are simply dirty they may be cleaned with a bit
of TV tuner cleaner, a toothbrush and some elbow grease. There are times when it
may be necessary to resort to using household cleanser and a small wire brush
chucked in an electric drill to clean the sockets. From the standpoint of safety
it would be wise to use a battery-operated cordless drill. There is no sense in
risking electrocution for the sake of repairing a turn signal system!
On some older cars, especially if the lamp sockets are made of
aluminum, the sockets are often corroded so badly that no amount of physical
scrubbing will repair them. The obvious solution is to replace the sockets if
you can find replacements. Let's suppose you can't. (We're not licked yet!)
Some may look on this last resort as "cheating" and perhaps
they are correct, but it will safely put the vehicle back on the road until
replacement sockets are found. The last resort solution is this: Purchase
replacement lamps with brass bases. Solder a pig-tail ground wire to the brass
base of each lamp, thread the wire through the socket (even if you have to drill
a hole for it) when inserting the lamp into the socket. Connect the pigtail
ground wire to any good, clean ground, either in a nearby section of wiring
harness or directly to a chassis bolt. The length of the pigtail ground wire
will be determined by the distance from the lamp socket to the selected ground
If this last resort fails to restore the turn signal system to full
operation it will be necessary to make a physical and eyeball inspection of the
turn signal circuit, wire by wire. This is not as difficult as it sounds if an
electrical map is drawn of only the turn signal circuit by consulting the
vehicle wiring diagram. As an example, such a map is shown in Fig. 2. It is for
a 1963 Triumph TR4. When making the map, indicate the wire colors to make the
circuit tracing job easy when actually working on the circuit in the vehicle.
With the map in hand, begin at the solenoid (2) of Fig. 2 and follow
wire by wire through the circuit. For instance, in Fig. 2, the lead from the
solenoid (2) to the ammeter (3) is marked N. The color code chart shows that N
indicates a brown wire. Make a visual inspection of the brown wire, paying
special attention to the condition of the terminals at its ends. If they are
dirty, corroded, or hanging by a thread of copper wire they must be thoroughly
cleaned and/or replaced. If the decision is made to replace them be sure to
solder the replacements to the harness. Do not trust a crimped connection to
perform with the same efficiency as a soldered connection!
There are about 14 wire terminals in the circuit of Fig. 2 between
the solenoid (2) and terminal #3 of the flasher unit (9). If each of these
terminal-to-wire connections is just slightly inefficient it is easy to
understand that the 14 poor connections in series add up to trouble in the
If a physical inspection of the individual wires seems to indicate
that all is well, yet the circuit is not operating properly, we may temporarily
bypass whole sections of the circuit with a jumper wire to make a test. Suppose
in Fig. 2 we think there are some poor, hidden connections between the solenoid
(2) and the flasher (9). A temporary jumper wire may be connected (see dashed
line in Fig. 2) from the solenoid (2) to terminal #3 of the flasher (9). This
temporary jumper bypasses the ammeter (3), the voltage regulator (4), the
ignition switch (5), the fuse (6), the in-line connector (8) and all associated
terminal-to-wire connections in the bypassed section. If the circuit now
operates normally, or with marked improvement, chances are that the problem is
in some part of the circuit that is being bypassed. For those vehicles over 15
years of age, oxidation at the terminal-to-wire connections should be suspected.
Inspect very carefully at points where the wiring harness passes
through rubber grommets. Over the years, the rubber deteriorates, and road
vibration can cause the wire insulation to wear through. Where this happens, the
bare wire rubs on the chassis ground and can cause intermittent electrical
problems if you're lucky. (If you're not lucky, the wiring harness simply
catches on fire, resulting in considerable unsolicited attention from
And now a word about oxidation. Oxides are the compounds formed when
metals combine with oxygen. Oxides are insulators. Insulators are notoriously
poor conductors of electricity.
If the headlights seem dim, if there are nagging and intermittent
electrical problems, if the vehicle is old and if inspections similar to those
mentioned to this point fail to resolve the problem(s), there is a high
probability that oxidation is the cause. Even a cursory inspection will reveal
that almost all the terminals at the ends of the wires in the wiring harness
(regardless of the make of the car or country of origin) are crimped, not
soldered. Regardless of how firmly the crimp was made when the terminal was
attached to the wire (perhaps 20 years ago - more in some cases), oxygen will
get to the crimped connection. The oxygen will combine with the copper to form
insulating copper oxide, and over the years this oxide will constantly decrease
the efficiency of current flow between the terminal and the wire to which the
terminal is crimped.
A temporary solution is to wash the connections liberally with TV
tuner cleaner and re-crimp the terminals. Note: this is only a temporary
solution! For a permanent fix there are basically two choices: one, cut each
offending terminal from the harness and solder a new terminal in its place; or
two, replace the complete wiring harness.
Vintage sports cars are passionately loved by their owners and
drivers. A special breed of enthusiast keeps these cars on the road in safe
driving condition. Once the challenge to preserve these treasures is accepted,
it is in the best interest of all concerned to share information. The intent of
this presentation is to disseminate practical information among those who love
these vehicles and work to keep them rolling, insuring that future generations
will have the opportunity to enjoy and appreciate them as much as we do.
Damp Starting Problems
If your car is still slow
starting, or won't start in wet/damp weather, and you have checked and convinced
yourself that your battery is strong, the grounds and hot connections are all
good, timing, plugs, and points are all up to specs, it is now time to go to the
next step. You should seriously consider replacing your old, probably weak
and/or worn out stock 25k coil with a new, high voltage 35k or 40k volt coil.
They are available at reasonable prices. If you are a purist, rest assured that
the Lucas Sports Coil (Moss #143-200), is still available, although not
originally fitted at the factories. Most likely if all the other electrical
stuff is working well, you will solve your wet/damp starting problems with a
high voltage coil.
Try it, and if you are like me, you will wonder why you or Lucas
didn't do it 20 years ago.
Tail Lamp Reflectors
A significant improvement in tail lamp brightness can be achieved by making a
reflector out of silver mylar.
Don't bother trying to cut the mylar to exact size. It's too flimsy
to work with easily. Fold an oversized piece into quarters, and cut off the
corner to make hole just large enough for the base of the lamp. Insert the lamp
through the mylar as much as possible and attach the lens assembly. Trim the
excess with a razor blade.
You should be able to get silver mylar at a hobby or science shop.
Those big silver balloons at carnivals are made of mylar. Aluminum foil may work
but mylar is stronger.
While you're at it, clean the lens and lamp. Polish the lamp base,
socket, and contacts. Also check for a good ground contact.
To avoid acid residue build-up on battery terminal posts and cable clamps, place
a copper penny on top of the battery between the battery posts. (The copper
penny will usually stay in place without falling off.) The copper in the penny
will absorb the acid residue from the posts and keep the terminal posts and
cable clamps clean. On older batteries that appear to give off more acid
residue, add an additional penny and place each penny one to two inches from the
posts. Make sure that there are no exposed areas of the battery cables near the
post terminal clamps, since the stranded copper cables will also absorb acid
residue. In about 6 to 9 months, the penny will turn into a small lump of
greenish powder. Merely wipe off the powder with a paper towel and replenish
with another copper penny as required.
What Generators Do and Regulators Ought
Most people first learn about generators at night on a back country road in the
middle of nowhere. (Actually, about 100 yards from a house, but the middle of
nowhere is so much more depressing.) You have one of those "English sports
car needs minor electrical work" from the classified ads. Oh, the man who
sold you the car was honest; the car was most certainly English and it did need
electrical work. Anyway, after standing over the open engine compartment and
alternately thumping on the generator, the control box, and the flashlight, you
conclude that although flashlights improve with thumping, generators and control
Perhaps the best way to come to grips with old electrics is by
gaining an understanding of what makes them work. Contrary to popular belief,
the operation of a Lucas generator
is not based on some magic incantation - it is based upon five fundamental
properties of electricity and magnetism:
1) Electric current in a coiled wire will create a magnetic field.
2) Wrapping the coil of wire around a soft iron core will intensify
the magnetic field.
3) The strength of the magnetic field will vary with the current in
4) Rotating a loop of wire in a magnetic field will induce a voltage
in that loop of wire.
5) The strength of the induced voltage is dependent upon the strength
of the magnetic field and the speed at which the loop of wire is rotated.
A generator is composed of five parts. The armature (1) is made up of
coils of wire wrapped around an iron core, and it is the armature which rotates
when the generator pulley is turned. The brushes (2) are the spring-loaded
contacts which transfer current from the armature to the electrical system. The
brushes actually rest against a segmented ring at one end of the armature; this
ring is called the commutator (3). Inside the generator body are the field coils
(4) (also called field windings) which are wrapped around the field poles (5),
which are essentially pieces of soft iron. It is current in the field windings
that produces the magnetic field in which the armature rotates.
When the engine is turning over, the armature is spun by the fan
belt. In the presence of a magnetic field (generated by the field coils), a
voltage is induced in the armature windings. When the voltage in the armature
windings is greater than the rest of the system, current will flow from the
armature terminal of the generator (usually "D") to the corresponding
terminal (also usually "D") of the control box or voltage regulator.
The control box (or voltage regulator as most of us call it) has two
main parts. The cut-out relay (6) prevents current from flowing to the generator
from the battery when the generator's output voltage is lower than battery
voltage. The second part of the control box is properly called the voltage
regulator (7). This strengthens or weakens the magnetic field in the generator
according to the needs of the battery or other electrical system components.
Remember, the stronger the magnetic field, the greater the voltage induced in
the spinning armature.
The cut-out relay consists of an iron core with a "shunt"
and a "series" coil wrapped around it. The shunt windings (8) are
connected between the generator armature terminal "D" and a ground
terminal (usually marked "E") on the control box. This means that the
internal generator voltage is always impressed upon the shunt windings. The
series windings (9) are wired so that all the generator output current passes
through them before going to the electrical system in general.
Fixed above the cut-out core is a spring arm that carries a contact
(10) which is connected to the series windings of the cut-out core. Output
current from the generator can only pass on to the electrical system and the
battery when the contact arms are touching. Spring tension normally holds the
contacts apart so there can be no current flow in either direction.
When the armature in the generator is spinning fast enough, (about
1000 generator RPM or 750 engine RPM) the current in the shunt windings (8) of
the cut-out relay will generate a magnetic field strong enough to overcome the
natural spring tension of the contact arm. The arm snaps down and the two
contacts touch. Current now flows through the series windings (9), across the
contacts and on to the battery through the output terminal (usually
"A") on the control box. Current in the series windings actually
intensifies the magnetic field around the core of the cut-out relay, and this in
turn holds the contacts even more firmly together. The point when the contacts
close is usually adjusted so that the internal voltage of the regulator is about
12.7 to 13 volts.
When your engine slows to idle, the armature slows as well. This
means that the voltage induced in the spinning armature decreases. Lower voltage
reduces the strength of the magnetic field holding the series winding's contact
arm closed. Eventually, the weakened magnetic field can no longer hold against
the arm's spring tension and the contacts open. (Note: the way in which the
contacts open is actually somewhat more complex, but this description will do
for our purposes.) This immediately stops all current flow to or from the
generator. The point at which the contacts open (around 8.5 to 11 volts) is
known as the drop-off point.
If the series winding contacts did not open at low generator output,
the higher battery voltage would flow back through the control box into the
armature's fine wire windings. The reverse flow would melt the windings and
thus, destroy the generator. Now you know one of the reasons why the control box
is so important.
other part of the control box, the voltage regulator (7), acts to limit the
voltage in the charging system to a safe value by controlling the internal
voltage of the generator. The voltage regulator, like the cut-out, has a shunt
winding (11) made up of many turns of fine wire wrapped around a soft iron core.
Suspended above the regulator core are a pair of contact points (12), again like
the cut-out relay. However, these points are normally closed, rather than open.
The function of the regulator is to break this connection. When generator
voltage is low, the current in the shunt windings is small, so the magnetic
field is too weak to overcome the spring tension in the arm holding the contact
points closed. When the points are closed, the output current from the generator
(entering through the "D" terminal) goes through the regulator frame,
through the regulator contact points (13) to the field terminal on the control
box (usually "F"). From the field terminal on the control box, the
current flows to the field terminal ("F") on the generator and then
through the field windings (4) around the field poles (5) of the generator.
Since we have a direct connection through the regulator contacts,
current in the field windings (4) is at a maximum. Consequently, the magnetic
field (in which the armature spins) created by the current in the field windings
is also at its maximum. Because the magnetic field is at its strongest, induced
voltage in the armature is also at its highest. (The voltage induced is directly
related to the strength of the magnetic field.) As the voltage in the generator
increases, the current in the shunt windings (11) of the regulator relay
increases, which in turn increases the strength of the magnetic field trying to
pull the regulator contacts (12) apart.
When the field strength finally overcomes the natural tension of the
contact arm and the regulator contacts are separated, the direct connection
between the armature terminal "D" of the generator and the field
terminal "F" of the control box is broken. While the direct connection
has been severed, there still exists a way for the current from the generator to
return to the field windings.
This second path is through a short piece of resistance wire, and the
built-in resistance reduces the current passing through the field windings
inside the generator. The reduction in current in the field coils reduces the
strength of the magnetic field in which the armature is spinning. The induced
voltage in the armature windings falls, and so generator output falls as well.
With reduced generator output, the current in the shunt windings (11) of the
regulator is also reduced, and the magnetic field produced by the current in the
shunt windings (11) is likewise reduced. When the strength of the magnetic field
is no longer enough to hold the regulator contacts (12) apart, they snap back
together, and direct contact between the generator output and the field windings
Since current is no longer flowing through the resistance wire, the
current in the field windings of the generator is increased, which strengthens
the magnetic field inside the generator. The induced voltage in the armature
increases, and the generator output also increases. As generator output
increases, current in the shunt windings (12) of the regulator increases once
again until the magnetic field is strong enough to pull the regulator contacts
apart. As before, with the direct connection broken, the current to the field
windings is reduced by the passage of current through the resistance wire. The
strength of the magnetic field in the generator falls, and so the generator
output falls. The cycle described here takes place very quickly; so quickly that
the contact points seem to vibrate.
We've now traced the system through its entirety. With this knowledge
in hand, you'll be able to entertain your companions with a profound
dissertation on the fundamental properties of electricity and magnetism which
make thumping on the generator and control box useless. We all know that once
the magnetism has leaked out, there is nothing anyone can do.
The Five Dollar Insurance Policy
If I told you that you could
purchase an insurance policy that would protect your British sports car for as
long as you owned it for around five dollars, you would probably ask me if I had
a bridge to sell also! But, while I don't have a bridge, I can tell you how to
protect your baby for under five bucks.
Most British sports cars manufactured before 1968 only have two fuses
protecting their entire electrical system. Typically these fuses only protect
the horns, A-2, the purple wires on the fuse block, and the accessories, A-4,
the green wires on the fuse block. A fuse on the horns is handy to remove when
the horn button sticks and your neighbors are threatening you, and your
accessories such as the stop lights, turn signals and wipers are duly protected
from staging their own version of the Chernoble melt-down. Some of the most
important and largest current-using circuits are not protected from electrical
problems and short circuits. The circuits that I'm referring to are (surprise!)
the headlamps and side lights. These circuits are in constant use, unlike all
the others that enjoy only intermittent use. A worthwhile modification to
pre-1969 British sports cars is to fit fuses to these unprotected circuits. This
will protect the car's wiring system from damage and the whole automobile from a
When an unfused circuit, like that of the headlamp, develops a short
circuit, the wires will get red hot and burn away their plastic insulation.
Should these bare wires contact anything combustible, such as interior material,
grease or gasoline, you can guess the resultsyou do carry a fire extinguisher,
An easy way to protect yourself and your British baby is to fit what
is known as an "in-line fuse". An in-line fuse is a small plastic
holder containing a replaceable standard automotive fuse for attachment in a
These little wonders are placed usually between the switch and the
electrical device in the wiring. For example, on the headlamp circuit, put the
fuse between the headlamp switch and the dipper switch, and for the marker
lights, between the switch and the group of red wires. Or, a single fuse can be
placed between the headlamp switch and its source of power on cars with separate
ignition and headlamp switches. Personally, I prefer to protect each circuit
with its own fuse. (See diagram.)
The wonderful thing about in-line fuses is that they can be easily
installed, and also, easily hidden for Concours fans. If a problem arises in
that circuit, the fuse will blow, stopping any further damage. You'll also know
that the problem is limited to just that circuit, not the whole car, when it
comes time to trouble-shoot the problem. Moss stocks these units under part
#146-750. Use a 25 amp. fuse, #146-710, for most circuits, or a 35 amp. fuse
#146-700, if you are using Quartz Halogen headlamps.
To install an in-line fuse, first consult your shop manual for the
wiring diagram to find how the circuit is wired and the color code of wires in
question. Next, disconnect the battery, otherwise you will be cutting into a
"live" wire, and while there isn't enough voltage to hurt you, you
want to avoid any short circuits while you install the in-line fuse. Be sure to
solder or use the proper type of connectors when joining wires together; just
twisting them together and slapping some tape around them creates problems
instead of preventing them.
Often, you can simply cut the existing wire from the switch and
install the in-line fuse in the middle of the wire, leaving enough distance from
the switch so you don't have to stand on your head to change the fuse.
If the wire isn't long enough to handle easily, you may extend the
wire using additional wire of matching size and approximate color. Installation
is as follows: Cut the wire in a handy location between the light and its on-off
switch, then remove about 3/16" of the insulation from each end. On one
end, slide on the plastic cap, followed by one of the metal contacts, which you
will solder to the end of the wire.
On the other loose end of the wire, slide on the longer plastic tube,
followed by the spring and the other contact that you will solder in place.
Insert the fuse in the longer tube and screw the cap in place by pressing down
and turning it about a quarter turn and the job is done! It's also a good idea
to mark the outside of the fuse holder with a felt-tipped pen so you can tell
the circuits apart. At $1.55 each, you can afford to protect all the unfused
circuits in your car and ultimately your car itself!
Ballast Resistor Ignition System
ignition coils suffer the disadvantage of being designed to operate best at
about 12 volts. Unfortunately, a 12 volt battery often produces as little as 7
volts when "run down" because of excess starter operation, especially
in extreme cold. To produce optimum coil performance (and hence nice fat sparks
at the spark plugs) under such adverse conditions, the "ballast
resistor" or "ballasted coil" system was developed.
This system uses a coil which is designed to be most efficient at
about 8 volts. For starting, full battery voltage is supplied! This makes this
system as efficient at low battery voltage as a "conventional" coil is
wlth the battery supplying a full 12 volts. (For any battery voltage above the
coil's design voltage, it's even better
an "overboost" condition.) However, an eight volt coil
cannot be run continuously at 12 volts without overheating and failing. As soon
as the starter switch is released, the coil no longer receives full battery
voltage. It is then powered through the ballast resistor which reduces the 12
volts (the generating system is now working) to the coil's design voltage.
Back to the Basics - Your Ignition
This is the first of a series of articles on basic tuning techniques to help you
maintain your car to original factory specifications. Since the ignition system
must be in good order before any other systems, such as the carburetor(s), can
be properly adjusted, we will begin with a brief discussion on ignition timing
procedures. These instructions assume that the ignition system components
(wires, spark plugs, distributor and its parts) are in good workable condition.
Ignition timing refers to the point during the combustion cycle at
which the spark plugs fire, and is expressed in degrees of crankshaft rotation
in relation to the top dead center (T.D.C.) position of the pistons.
Specifications for timing include the number of degrees before or after top dead
center, and the required engine speed at which the setting must be made.
Supplemental instructions such as "disconnect vacuum advance line" may
also be given. When a specific engine speed (other than "static") is
given, or for electronic ignition systems, timing must be done using a
stroboscopic timing light. For most of our older British sports cars, however,
"static" timing is specified. This simply means that the timing is set
with the engine not running.
Before considering checking or setting the ignition timing, it is
imperative that the condition of the points and the point gap be checked and
reset, if required. While most Lucas point type distributors require a point gap
of .014" to .016", check your workshop manual for your particular
distributor's requirement. Adjusting the point gap is really an indirect way of
setting what is known as the dwell angle. This is the angular period of rotation
of the distributor cam during which the points remain closed. Setting the point
gap with the aid of an inexpensive dwell meter is much more accurate than
setting with a feeler gauge. Do not neglect this setting - the dwell angle is
one of the most important settings on a car, having serious effects on
performance and fuel economy.
All engines have some sort of timing mark - one or more marks on the
crankshaft pulley or fly-wheel, which align with a fixed mark on the timing
chain cover or engine block. A pair of these marks will align when the piston in
the "timing cylinder" (usually No. 1 cylinder) is at top dead center.
Consult the appropriate workshop manual for information specific to your engine.
Occasionally, the timing mark or pointer may be missing or improperly
positioned. (This is fairly common on TR2-4A, where the crankshaft pulley is
easily installed with the timing mark in the wrong position in relation to the
crankshaft throws.) When these conditions exist, top dead center may be found by
removing the appropriate spark plug and observing the piston movement through
the spark plug hole while turning the engine over by hand. When the piston
reaches its highest position, it is at top dead center. When you are satisfied
that top dead center has been accurately located, mark the position for future
The static timing procedure is not difficult. The only equipment
required is a 12-volt test light. If a commercial test light is not available, a
substitute may be easily made by soldering two wires to a 12-volt light bulb;
one wire to the side of the base, and the other to the bottom contact. For
convenience, alligator clips may be installed on the other ends of the wires.
To static time your engine:
1) As accurately as possible, locate the piston of the "timing
cylinder" at top dead center, on the compression stroke. This is achieved
by noting the position of the ignition rotor when the piston is at top dead
center. If the rotor points to the contact on the distributor cap which leads to
the spark plug of the "timing cylinder", the piston is on the
compression stroke. If the rotor points away from that contact, the piston is on
the exhaust stroke, and the crankshaft must be rotated one full turn to bring
the piston to top dead center on the compression stoke. Check that the timing
marks line up correctly. (If the distributor has been removed from the engine,
consult an appropriate workshop manual for proper re-installation instructions.)
2) If your vacuum advance unit has an adjuster, you may either
proceed with the instructions in this paragraph, or skip it and go to paragraph
3, continuing from there.
If your pulley or indicator is marked with degree settings, turn the
crankshaft until the single mark and the appropriate degree mark line up. If
your pulley or indicator is not marked in degrees, use a timing degree wheel
(Moss # 384-910) to set the crankshaft to the proper advanced or retarded
setting as specified for your engine. It is essential that a reliable workshop
manual be consulted for this specification. The piston of your "timing
cylinder" is now in the correct firing position, and the distributor must
now be adjusted to is firing position.
3) Loosen the distributor clamp to the point where the distributor
may be rotated freely. Set the adjuster on the vacuum advance unit (if present)
4) Connect one wire of the test light to the low tension contact on
the distributor, and the other wire to a good ground. (The low tension contact
is where the thin wire from one side of the ignition coil connects to the
5) With the ignition on (but the engine not running), rotate the
distributor body slowly in the opposite direction of the rotor's rotation until
the test light lights up, indicating that the points have just opened. Do this a
few times until you have accurately determined the exact point at which this
happens, and re-tighten the distributor clamp bolt.
6) For distributors with adjusters on the vacuum advance unit, only
if paragraph #2 was skipped:
With the piston of the "timing cylinder" at top dead center
(see 1.), the adjuster on the vacuum advance unit may be used to "dial
in" the correct static advance setting. One division of the scale is equal
to four degrees. Count the "clicks" on your adjuster nut between
divisions, and divide by four for the number of clicks per degree (generally
about ten per degree, but check your individual distributor). Multiply this by
the number of degrees advance you require, and set accordingly. Refer to a
reliable workshop manual for this setting. Be sure to turn the adjusting wheel
in the direction of the "A" to advance, in the direction of the
arrowed "R" to retard.
7) Disconnect the test light and start the engine. If it does not
start, make sure that you remembered to replace the rotor after adjusting the
points. Don't feel foolish if you find it on top of your battery or wiper motor
- there probably isn't a single auto mechanic dead or alive who hasn't had this
Crane XR-700 Ignition System:
Of all the systems that enable your British automobile to keep rattling down the
road, fewer are more trouble-prone than your ignition system. The main culprits
are usually the contact breaker points and condenser. The usual scenarios are:
1.) the points (after too many miles since the last replacement) finally wear
out the rubbing block, close up their operational gap and burn up their contact
faces, 2.) (my personal favorite) the condenser finally shorts out and takes the
points with it by frying the contacts.
There are other little problems like the fact that the distributor
body and shaft can wear to the point that the points' cam is no longer rotating
in perfect circles, but is now changing its orbit at will from circles to
ellipses (and sometimes the cam opens the points completely and sometimes it
doesn't). Not only does this affect the period that the points are closed
(dwell) but it can effect the ignition timing as well.
The golden rule of British cars (neé Murphy's Law) now applies here;
any of the above will happen to you at the single most inconvenient time of your
life... usually miles from anywhere... in bad weather, when you need the car the
most. Also, its going to cost you piles of gold (hence the golden rule) to get
towed to the nearest town, whose local auto parts store will not have the parts
you need, anyway!
Point ignition systems have been around since the dawn of the
automobile age and so have failures of its basic components - the points and
condenser. British Leyland recognized the shortcomings of the point type
ignition systems, and in the later production runs of the MGB and TR7, these
cars were fitted with electronic-type ignition systems. Unfortunately, early
Lucas systems incorporated a number of flaws.
The standard Lucas System is renown for failure of the ignition
amplifer unit, (the black box under the coil). It has never been a question of
"will it fail", only "when". The Crane XR-700 is a less
expensive and permanent solution to this problem (distributors with point
systems use Moss #222-335 kit, those with electronic ignition use #222-325).
What is an "Electronic Ignition System"? It is an ignition
system that uses non-mechanical means to trigger the ignition coil to fire,
thereby eliminating the trouble-prone points and condenser completely, and
replacing them with a system that is triggered by either a magnetic pulse or
The Crane (a.k.a.
Allison) XR-700 Ignition System works on the optical principal, with the points
and condenser being replaced by an optical pick-up and a "shutter"
wheel attached to the distributor shaft. The system works using a light emitting
diode (L.E.D.), shining a beam of light to a photo-optic cell immediately
opposite. These two are located in the optical pick-up, which has a slot through
it in which the flat surface of the shutter rotates. The shutter wheel has the
same number of evenly spaced slots in it as the engine does cylinders, and is
fixed to the distributor shaft either by self-locating spring clips on the point
type distributors, or by the original snap ring and washer when used on the
later electronic distributors. As the wheel rotates, a slot will pass over the
photo cell, allowing it to see the L.E.D., and in conjunction with the ignition
module, signal the ignition coil to fire. The great feature is that there are no
points to wear out, no condenser to short out and a L.E.D. never burns out!
Also, if the shaft or body are worn in your distributor, it will have negligible
effect, as the shutter wheel is still wide enough to compensate, regardless of
the shaft's orbit. Because there are no mechanical parts to wear out with the
Crane XR-700 installed, you will never again have to adjust your timing or
I know this sounds incredible, but in 85,000 miles on my MGB GT, my
timing hasn't changed one degree. The added bonus is your future tune-ups will
take less time to complete and cost less. After choosing the appropriate kit for
your car, the first step is to find a location in the engine compartment to
place the ignition module. These leads are sufficiently long enough to allow
mounting anywhere in the engine compartment, so even you Concours fanatics can
install a XR-700 and mount it out of plain sight. On the car used in this
article, a '71 MGB roadster belonging to Moss' own lovely and talented Jill
Jones, I chose to mount the ignition module in a empty space next to the
ignition coil on the right inner fender well and across from the distributor.
The kit provides two self-tapping screws in the parts bag for this task,
although I used one pre-existing threaded hole and the screw in it that also
mounted the wiring harness, so I had only to drill one hole to install this
The next step is to connect the various wires as dictated by the
appropriate Crane diagram. Jill's car is negative ground, so the connections
were straightforward, as the wires are color-coded and labeled as to the
terminals they connect - practically foolproof.
Now that we have installed the ignition module on Jill's car, let's
address installing the optical pick-up. The first thing to do is to set the
engine so its timing marks line
up on Top Dead Center, cylinder number one. If in doubt as how to achieve this,
consult your workshop manual. Now follow the spark plug wire from #1 cylinder
back to the cap, and mark both the cap and the side of the distributor body with
a felt tip pen. On BMC series A (Midget) and B (MGB, MGA) motors, it may be
easier to install the optical pick-up in the distributor if you remove the
distributor from the engine first. To install the optical pick-up, remove the
points and condenser, or on Lucas electronic systems, remove the old pick-up and
cable conduit. On Jill's MGB we'll hang on to the plastic terminal that the low
tension lead connects to; this is the part that fits into the distributor body
and protrudes into the cap itself.
Next we will install the optical pick-up with its adjusting arm and
mounting foot on the breaker plate of the distributor, using one of the screws
that originally mounted the points. On electronic distributors, use the screw
that held down the plastic conduit. Now fit the shutter wheel to the distributor
shaft and slide the optical pick-up into place. Don't tighten all the screws
completely until you reinstall the distributor, and make sure that there is
plenty of clearance between the shutter wheel, pick-up and rotor arm, so that
they don't rub anywhere. On Lucas electronic systems it may be necessary to
slightly bend the studs that held down the original pick-up so that they don't
contact the shutter wheel.
You'll find that on most Lucas distributors, you will have to set the
optical pick-up right down on the breaker plate to get any clearance above or
below the shutter wheel. Turn the distributor body so the rotor arm points at
the line you marked on the body, and adjust the mounting foot so that you can
slide the pick-up across the nearest slot in the shutter wheel. Run the gray
cable out of the distributor body through the original grommet on Lucas
electronic systems, or on earlier cars like Jill's MGB, take the original low
tension insulator and drill out the bolt passing through it. You will find that
the cable will just fit in the hole and with a little silicone gasket goo, you
can affect a weather-tight seal.
Be sure to leave enough extra cable inside the distributor body to
allow movement of the breaker plate if the distributor has vacuum advance
attached. A small tie-wrap is included in the part bag for this purpose. After
routing the cable out of the distributor, you can install the Molex plug, taking
care to match the colors to the other half of the plug.
If you have removed your distributor, now is the time to reinstall it
back in the block. Slacken the clamp bolt and rotate the distributor body until
the rotor points are at the line you marked earlier and connect the optical
pick-up to the ignition module with the Molex plug. Next, remove the high
tension cable from the distributor cap and tape it somewhere where the end of it
is about 3/8" from a good ground.
Switch on your ignition and you can make final adjustments to the
optical pick-up. This is done by sliding the pick-up in a clockwise direction
toward the approaching slot. As the pick-up passes the slot, the L.E.D. will see
the photo cell and fire the ignition coil, resulting in a spark jumping from the
high tension lead to the ground. Besides being able to see the spark, you should
be able to hear it as a cracking noise. You want to slide the pick-up until the
coil fires and no further, then tighten the screws to secure it. You may want to
try this a couple of times until you are comfortable with its final position.
After the final adjustments of the optical pick-up make sure that
nothing rubs and that the distributor cap fits with no interference. On MG
T-types and Austin-Healey 100s this is very important, as the space under the
cap is at a minimum. Now we can set the timing to the manufacturer's specs. on
Jill's car for the last time, as the timing will never change from wear in the
distributor. However, it's a good idea to check the timing, say, once a year, to
see if there is any change due to timing chain wear or wear in any other
While we are in the neighborhood of the ignition system, it's a good
idea to examine the rest of the components. On Jill's car, the distributor cap
and rotor were renewed, her ignition wires were replaced with a set of Lucas
Premium Ignition Wires (#171-660) and her tired old coil replaced with a more
powerful Lucas sports Coil (#143-200). Last but not least, you'll need a set of
new and properly gapped spark plugs.
The end result of our labor, according to Jill, is a car that runs
smoother, is more tractable, starts easier, and will require less maintenance.
Mallory Dual-Point Distributor
In this article we will examine yet another alternative ignition system for your
British sports car, the Mallory Dual-Point Distributor. What makes the Mallory
unique among point type ignitions, is, as the name implies, it has two separate
sets of points to do the work of one. What are the advantages to using two sets
of points? In the Mallory distributor, one set of points opens the primary
circuit and the other closes it, giving a longer period of dwell (the period of
time that the points are closed, expressed in degrees).
The dwell period is the time when the secondary windings in the
ignition coil charge the magnetic field up for another high voltage blast when
the points open (20,000-40,000 volts!). It can generally be said that the longer
the period of dwell, the higher voltage the spark. On most four cylinder
engines, the dwell period is about 60°, but the Mallory Dual-Point Distributor
has a dwell period of 72°, so even if you choose to use your stock coil, you
will still have a "hotter" spark, as the coil has more time to charge
itself up than with a conventional distributor. This is accomplished in the
Mallory unit by the following process. In the four cylinder distributor the
point cam has eight lobes, and as it rotates, it opens the primary set of points
completely, triggering the coil. Then the lobe rotates another 8° and opens the
secondary set of points. Shortly after the secondary set has begun to open, the
primary set closes, and the ignition coil starts charging even though the
secondary set is still open. After the secondary set has closed the process
starts again for the next cylinder.
Why not just crank open the points for more dwell in your stock
distributor? You could, but this would have an adverse effect on the ignition
timing and the points would wear in short order, as they are designed to work at
a specified gap, all of which would result in a loss of performance and economy.
Another feature of the Mallory Dual-Point Distributor is the fact that it has a
full centripetal advance unit, rather than the part-centripetal, part-vacuum
advance system used on the stock Lucas distributors. This feature may make it
illegal for use on pollution-controlled vehicles (check your local and state
laws before using this unit on the street) but makes it perfect for use with
high performance engines equipped with sidedraft carburetors that often lack a
vacuum port for use with a stock distributor. The Mallory unit is also easily
adjustable for total amount of ignition advance, and comes preset at 28°
allowing the serious enthusiast the ultimate in tune-ability. The Mallory
Dual-Point is supplied without a drivedog or gear, which must be transferred
from the old distributor. Mallory has been making high performance ignition
systems since 1932, was even a popular modification to MG TCs when they were
Today there is a Mallory Dual-Point to fit most British cars, so if
you're looking for the ultimate in high performance ignition systems, look no
further than the Mallory Dual-Point distributor.
Diagnosing Wiring Troubles!
(Words of Wisdom to Live and Drive By)
Does your car let you down every time you try to start it, or those wipers only
work when it is not raining? Perhaps the indicators go dim every time you apply
the brakes, and the horn only operates when the lights are off.
Before you go out to buy new lights, horns, switch gear, voltage
rectifiers and anything else that carries an electrical current, it may be
worthwhile spending time checking out the wiring rather than shelling out on new
Quite often I have found that electrical components supposedly
faulty, are perfectly all right, i.e., "blown" headlamps which are
intact, switches that work when connected to a multi-tester, horns that stop
making funny gurgling noises and operate correctly when connected to the battery
for a test.
Many electrical faults are caused by two frequently overlooked
factors, either working separately, or together to produce a variety of
interesting visual and sometimes pyrotechnic effects. The first of these factors
is simply caused by age and the climate - electro-rheumatism if you like. The
second is caused by that stalwart of the motoring world, Captain Accessory!
I am always surprised by the large number of good quality products on
the market (and this does include radios, etc.) which are let down either by the
cheap, easy-to-use connectors sold with the kit, or by "hash wiring"
on the part of the installer. Fitting any accessory should be dealt with in the
same way that any other task should be undertaken on a vehicle - properly.
Connections should be mechanically and electrically sound.
The worst electrical problems I have faced have been caused by "bodged"
wiring or faulty connections. Easy-to-use connectors often provide me with hours
of entertainment, as does unwrapping electrical insulation tape to find wires
that have been just cut, stripped back and twisted together. It always works for
And it's not bodged wiring - some products are of an appalling
quality. For example, I have tried various different HT leads in my car to
"improve the quality of the spark", "reduce resistance", and
"provide better ignition". Moss of these leads have been useless. It
doesn't matter two hoots that the PTFE casing and superior quality copper core
offers less resistance than the normal standard item - what matters is that if
the cap doesn't fit the spark plug, it will just bounce off. One famous make had
such appalling connections that it would not fit into the standard Lucas
If you are going to tackle any electrical work for your car, then do
it properly and do it once. Throw away those cheap connectors ad get the right
tools to do the job properly - because I can guarantee that if you don't, that
one day you'll wish you had - or even worse, you'll get rid of the car because
it keeps going wrong. (I've picked up a few cheap cars like that which sing
after two or three house with a soldering iron!)
Get the Right
1. Soldering Iron - Get one with: 5 to 15 watts output, stay clean
tips, decent stand, and PTFE leads (which make the iron easy to handle.
2. You probably already own one of those multi-purpose devices that
cuts, strips wires and fits connectors. Throw it in the trash. Buy instead: Long
Nose Pliers, Side Cutters, Wire Strippers, Insulation Tape, and Solder (60 - 40
lead/tin mix with flux incorporated).
3. Connectors - Get the type of connectors that are already in use on
your car - spade connectors and bullet connectors (that can be soldered) and
throw the crimp connectors into a bin!
Three important safety tips:
1. Disconnect the Battery
A fully charged battery can use around 120 amps to turn over a cold
car engine. Making a mistake and accidentally connecting the positive to the
earth can have some interesting affects, i.e.:
i. Any wire involved in a direct connection will act like a fuse and
melt (this includes HT wire).
ii. The battery could explode if an HT wire does not fuse quickly
iii. 120 amps is enough to weld your screwdriver to any object very
iv. You can receive nasty burns if you use yourself as a suitable
earthing point. (Remember DC current differs from AC in that it does not change
direction - once you get to grips with DC it won't let go!)
2. Holding the soldering iron
Never grab the soldering iron if it starts to fall. Sounds obvious,
but there are still plenty of electrical engineers around who hold out their
left hand when greeting somebody!
3. Suitable wiring
Finally, make sure that the wires you are using have the correct
current capacity for the power they have to take. Using cable that is too thin
is the electrical equivalent of reducing three lanes of motor way into one -
total breakdown - if the current is much higher than the wire, the wire will act
like a fuse and melt.
1. Spade connectors
Strip back 1/4" of wire without ripping out half of the strands,
(if you have never used wire strippers before, have plenty of practice with some
old bits of wire) twist the strands together and solder the bare end.
Always heat the wire with the soldering iron and apply the solder to
the wire while it is still in contact with the iron. The wire must be hot enough
for the solder to flow into the wire strands - but don't keep the iron there for
too long, otherwise the outer sleeve of the wire will melt back. It is an art
Do not apply solder to the iron and then try to "blob" the
solder on to the wire - it never works because the solder "dries out"
as the flux evaporates, and then the resulting joint can become brittle and
prone to breaking (aka "Dry Joint").
Once cool, fit a spade connector sheath over the wire and then crimp
the connector to the wire as shown in the diagram The crimping makes a
mechanically sound connection, but this is not enough. Returning to the
soldering iron, you then need to apply heat to solder the wire to the connector
to ensure an enduring connection, just like they do at the factory.
2. Bullet connectors
Bullet connectors are needed where (A) two separate lengths of wire
are to be joined together or (B) where an extra wire is to be added to a main
Many bullet connectors can be crimped on as well as soldered to
enhance the quality of their connection, but the stock items used by BL tend to
be a bit more tricky and can only be soldered - so you must ensure that the
soldered connection is not dry!
Strip back 3/8" of cable and solder the strands. Insert in the
end of the bullet - it may help to "kink" the strands slightly to keep
the bullet in place - and then re-apply the soldering iron to the top of the
bullet. Allow it to heat up and then apply the solder through the hole at the
top of the bullet so that it can run inside, attaching the cable to the wall of
The advantage of these connectors is that, if corroded, the connector
block can be thrown away and a new one fitted without having to do any more
soldering. Also, they can provide multiple outlets for power, but watch out for
that current overload on the original feed wire!
The disadvantage is that the connector is a mechanical fit and prone
to electrical failure when corroded, which is why many cars start going wrong
after five year's use!
An Extra Fuse Box
If you are accessory mad, the use of a fuse box with a direct link to
the solenoid may provide a safe, efficient answer, rather than connecting
countless new wires onto an overburdened wire feed.
Again, make sure that the wire, from the feed to the box has
sufficient capacity to deal with any load place upon it (an in-line fuse may
further protect the entire system).
Is it worth the effort you might ask? Yes! A clean job is a good job!
1. If it's soldered, then the connections will be better, stopping
niggling electrical failures and dangerous burn-outs; the connectors are cheaper
2. The proper connectors often allow easier access for repair of
3. Stops wires from sparking and equipment lasts longer.
4. It looks better, too!
Finally, here are some good tricks to play on people wielding a
soldering iron on their car.
1. Blow up a paper bag and stand behind them. Burst the bag whenever
you see them cutting a wire or poking at something electrical with a
2. Try swapping solder for tinned copper wire. It's better than
watching paint dry. (The other version involves merely turning off the soldering
3. Offer to hold wires while they solder than swap one wire for a cut
off length of about 4" long and then wait for sparks to fly when they
realize they have just connected a wire that goes nowhere.
Bulb Replacement Tip
Tired of breaking those little sidemarker bulbs? Seems like every time you try
to pull one out or put one in, either the bulb breaks or you get your fingers
sliced on the housing. Here's an easier way. Take a 1/2" internal diameter
hose line length, and insert it over the bulb glass. Now you can press/pull and
turn with the length of hose, which neatly grasps the bulb without breaking it.
Different size bulbs can be similarly done with different hoses.
After skinning my knuckles and bruising the back of my hand in a struggle to
remove the two batteries in my pre-'75 MGB, I needed some help! Being reluctant
to use a terminal gripping strap, as this can seriously damage the battery, I
thought there had to be a better way. Indeed there is!
I took a piece of nylon strapping (about 1 inch wide, less than 1/16
of an inch thick and 33 inches long), wrapped it around the battery so that the
ends of the strap are to the top of the battery and the strap sits in the car
parallel to the car's length, and lowered the battery into its compartment. The
ends of the strap can be tied together with string or sewn together, and the
loop slipped over the battery. This strap, of course, stays in the car and
serves as an excellent handle to make removing the battery infinitely easier
without risk of damage.
Cut-Off Switch Tip
When restoration of my 1970 MGB was complete, I received many comments and
admiring glances from my friends. The trouble is, I also got them from
strangers-including some whose home decor probably included steel paneling!
Buying a false alarm system didn't seem to be the answer, and the
baddies didn't seem to mind sawing through the steering wheel if they found a
Club installed. My choice was to purchase a battery cut-off switch.
The problem was that my beautiful 'B wasn't pure, but had a few
modern touches added. My clock/cassette stereo would get amnesia every time I
used the switch, losing station presets and time of day.
The solution proved to be wiring a fuse holder from the negative
terminal to the body and inserting a 1/4 amp fuse. This allows the light to come
on when the door is opened, keeps the stereo's memory intact, yet will blow
under a heavier load, such as the starter.
Now I feel that my MGB will sleep in its own garage every night.
More on the Battery Cut-Off Switch
I have been following the correspondence on battery cut-off switches in recent
issues of Moss Motoring and feel compelled to add my tip. After completely
restoring my 1972 MGB, I too felt concerned that strangers were interested in my
car for purposes other than to look and admire. I listened to several solutions
put forward by my fellow club members but finally took the following action.
Since the batteries are located towards the rear of the car. I
installed a remote battery cut-off switch just behind the batteries IN THE
TRUNK! Once activated, the car will not start without turning on the switch and
the nice part about installing the switch in the trunk is that you lock up the
switch when you leave the car. Most joy riders only want to enter the car and
take off. On a roadster this poses no problem but with the cut-off switch locked
in the trunk, the unsuspecting thief cannot easily steal the car and will move
on to an easier mark.
Adding Turn Signals
I read with interest the article by Jim Rutledge on adding a hazard flasher to
older British cars, (Moss Motoring, Summer, 1996 Issue) and it was certainly a
simple, effective solution. It had, however, a couple of disadvantages. One,
which was mentioned, is that of a high flash rate. This also has the potential
to reduce the life of the flasher. The other drawback is that it requires the
ignition key to be on in most if not all, applications. Also the Editor's
suggestion for adding fuses should not be needed, as the turn signal circuit
should already be fused, and any current flowing through the modification will
be flowing through the existing fuse.
I would like to offer another simple solution but without the
drawbacks of the first solution. It requires the addition of only one, simple,
readily obtainable switch, and a second flasher unit, one specifically designed
for hazard flasher duty*.
Purchase a double pole-double throw (DPDT) switch from Radio Shack or
any other electrical supply house. Also purchase a flasher from an Auto Supply
store. Make sure the switch you buy does not have a "center-off"
position, as most switches found at auto supply stores do. For installation (see
diagram), simply cut the two wires mentioned in the previous article and insert
the switch in between the cut wires as follows.
The wires coming from the turn signal switch should be soldered to
the adjacent terminals at one end of the switch-it doesn't matter which end of
the switch, or which wire goes to which terminal. It may be necessary to add
extensions to the wires, in order to reach the switch depending upon where you
The other ends of the wires go to the adjacent terminals in the
center of the switch. The only requirement here is that the colors match on each
side of the switch. The two terminals at the other end of the switch should be
soldered together with a short length of wire, and a second length of wire
soldered between these terminals and the output terminal (marked L) of the
The input terminal of the flasher (marked X) should be connected to
any purple wire (or any wire that is fused and hot at all times, with or without
the key being on. In most British cars this will be a purple wire). If you use a
purple wire you shouldn't need a fuse. If you prefer, connect to a brown wire
and insert a fuse of 10 amps as close to the brown wire as you can. Of course,
all the normal cautions of wiring should be heeded.
If you would like to get really fancy, buy a three terminal flasher
and connect an indicator light between the third (marked P) terminal of the
flasher and ground. Position the light wherever it is convenient for you, and
now, when using the hazard flasher, the indicator will flash just like your
* The difference between a turn signal flasher and a hazard flasher
is this: A Turn signal flasher is designed to operate only under one specific
load condition. If a turn signal bulb is burned out, the flasher will not flash.
This is a safety feature designed to warn you of a burnt out bulb so you can
replace it. A hazard flasher, on the other hand, is designed to operate no
matter how many bulbs are burnt out! This too is a safety feature. Under any
condition you might be using the hazard flasher, it is more important that
whatever bulbs are working are flashing. The lights are needed now! Many of the
'heavy duty' turn signal flashers sold are, in reality, hazard flashers.
Troubleshooting Electrical Problems
If there is anything worse than a car that won't start I haven't found it. But
before giving up and having your car towed away (by someone who has no idea what
kind of car it is) consider the possibility that YOU, yes YOU, may be able to
repair it yourself. Stop and think what has happened. Have you been having
intermittent starting problems? If so, you may have a loose connection or dirty
contacts somewhere. Did the car just die while you were cruising along? Again it
could be a loose connection or maybe a short (although as we all know this is
highly unlikely in a British car!). Or has the car been stored for a while?
Again, maybe just dirty contacts such as the points. Maybe you're simply out of
gas or have a plugged fuel line. Everything can be fixed by a person with
average ability, as long as they can figure out what the problem is. About the
only thing you need to troubleshoot the ignition system is a multimeter. You can
get a cheap analog one (the kind with a meter) for $6.00, but don't waste your
money. Buy a digital one and you will be able to understand what the numbers
mean which is more than I can say for the analog type. You can buy one mail
order for about $13.00. A test light will do in a pinch but it's not a good
choice. There are times when you need to know the correct voltage as well as
instances that even a small amount of current indicates a problem. Since six
volts will light a 12 volt test lamp but one volt won't you can miss a problem
and not know it.
In order for the engine to fire it must get a high enough jolt of
electricity from the coil to the spark plugs. The first test is whether or not
current is getting to the plugs. It's possible to pull one of the spark plug
wires from the spark plug and hold it about a quarter inch from the block. When
turning over the engine you should see a strong blue spark. The problem that you
are going to face is that the rubber boot on the spark plug makes it impossible
to perform this test without sticking a screw driver or something else into the
boot, and then trying to hold this contraption a quarter inch from the block. A
better way is to pull the wire from the spark plug and use a spark tester. This
way there is no chance of getting a shock or mistaking the strength of the
spark. You can purchase a spark tester for about $7.00 at most auto parts
stores. You can also make one for about $2.00. Take an old spark plug and cut
off the electrode at the bottom with a hack saw. Then drill a small hole in the
metal part of the plug and attach a large alligator clip using a self tapping
sheet metal screw. To use the tester attach the alligator clip to a good ground
such as the engine block, attach the plug wire to the tester just as you would a
spark plug wire and crank the engine. Another advantage of using a spark tester
is that it requires the same voltage to fire the tester as is needed to fire the
engine. The small gap on a normal spark plug does not require as much current
once it is removed from the engine.
If this test is positive, and you are getting a good spark then you
know that the ignition circuit is in order, and your starting problem is
somewhere else. The most likely suspect would be in the fuel system. You could
also have a mechanical problem such as a broken timing chain.
The starting circuit is broken down into two separate circuits. The
secondary circuit is made up of the "thick wires" which are the spark
plug wires and the wire from the center of the distributor cap. It also includes
the distributor cap, the rotor, the spark plugs and one set of windings inside
the coil. In other words everything that carries the high voltage.
The primary circuit would be everything that's left. The battery,
ignition switch, points, coil wiring, and in some cases the ballast resistor.
Starting with the battery which supplies 12 volts, the electricity flows through
the ignition switch to the primary side of the coil through the SW (switch or +)
terminal on the coil then out through the CB (contact breaker or -) terminal.
Connected to the CB terminal is a thin wire that is attached to the distributor,
which in turn is attached to the points. The points are really nothing more than
a switch. Think of them as the switch on a burglar alarm. When the switch is
closed everything is quiet, but when the switch is open the noise starts. When
the points are closed the 12 volts of electricity from the battery is flowing
merrily on it's way from the SW side of the coil to the CB side of the coil and
then into the points. When the points are open 20,000 to 40,000 volts erupt from
the top of the coil. The increased voltage coming out of the coil travels
through the secondary circuit. It starts it's way down the thick coil wire into
the distributor cap, and is distributed to the spark plugs via the rotor to the
spark plug wires.
Assuming that you don't have any spark at the spark plug tester, you
need to work back from that point. You can take the tests by leaps and bounds,
thereby eliminating all components between two points, or test each component
separately. I would recommend at least the first time to check each component
individually. By doing so you may find a weak component that's adding to the
problem, but not directly causing it. If you have some extra time it would be a
good idea to run these tests before you have a problem. By doing so you can
familiarize yourself with what should happen when everything is working
Checking the Primary Circuit
A good indication of whether or not the complete primary circuit is
operating correctly is by the intensity of the spark coming out of the coil
wire. To test the spark, remove the coil wire from the distributor and hold the
wire a quarter inch from the engine block. With the ignition switch on open,
close the points with a screw driver. If the primary circuit is functioning you
should get a strong spark coming out of the coil wire. If you're not sure what
to look for, the points are made up of two parts. One part looks like a flat
spring and it has the "point" attached to one end. This is the movable
point. The other point is stationary and is screwed to the bottom of the
distributor. If you turn the engine over with the distributor cap off it will
become apparent which part is which.
If this test reveals no spark you will have to figure out just how
far along the power has traveled from the battery. The first check is to make
sure that you are getting power to the coil. With the distributor cap still off,
open the points. This can be done by quickly tapping the ignition switch,
solenoid button or putting the car in fourth gear and rocking it. Turn the
ignition switch on, grab your multimeter and put the positive or negative test
lead (depending if your car is positive or negative ground) to the battery side
of your coil and the other lead to a good ground. You should get a 12 volt
reading. If not, you have a problem with the ignition switch, the battery, the
wire between the battery and switch, or the coil. Try jiggling the starter
switch and if you now get voltage then either the switch or connections are
The purpose of the ballast resistor is to reduce voltage going to the
coil. Not all cars have a ballast resistor. If your coil has three wires
connected to it chances are that one of them is for a ballast resistor. If the
ballast resistor is bad the car may start but die out immediately. There isn't
much you can check. Try grounding the thin wire that runs from the coil to the
distributor-it's the CB or - side of the coil. Then with the ignition switch
turned to the on position (not the cranking position) measure the voltage from
the + side of the coil. You should get a reading of about five to seven volts.
If less than five volts it's not getting enough power which may mean a bad
There are three things that you want to check for with the coil. The
first is the internal resistance. Disconnect all the wires going to the coil.
Set the multimeter to the lowest ohms scale. Now with the meter connected to the
+ and - side of the coil you should get a reading of about one and a half to
three ohms. Much higher or lower than this indicates a bad coil. Next check the
secondary circuit. Set the meter to the high scale and put one lead on either
the + or - terminal. Put the other lead into the terminal at the top of the
coil. You should get a reading between 6000 and 30,000 ohms. This is one of
those tests that I mentioned in the beginning of the article that you should do
before you have a problem. Make a note of what your reading is and what scale
that you got the reading on. Then in the future when your coil is in question
you will know what to expect. The last test is for an internal ground. Set the
meter to the high ohms scale and connect one test lead to either the + or - side
of the coil and put the other lead onto the case of the coil. The needle should
not move at all. If it does the coil is internally grounded and must be
replaced. A tip for MGA owners is to make sure that the coil does not rest
directly on the generator. The vibration has a nasty habit of wearing a hole
through the case of the coil causing the power to arc from the coil to ground.
To test the points all your coil wires should be hooked back up and
your ignition switch on. The first check is to make sure that you are getting
power to the points. With the distributor cap still off, open the points. This
can be done as you did above by turning the engine with the key or solenoid
switch. Turn the multimeter to the DC volts scale and touch the probes to the
points. One on the movable point and the other end to ground. You should get a
reading of about 12 volts. If not, then you are not getting power to the points.
If you have 12 volts up to the coil then check the thin wire from the CB (-)
side of the coil to the points, you may have a break in it. Assuming you are
getting power, you want to check the condition of the points themselves. To test
the points, turn the engine until the points are separated. As in the test
above, hold the coil wire about a quarter inch from the engine. With a
screwdriver touch the movable point to the metal plate below. What you are doing
at this point using the screwdriver as the points. If you now get a good spark
coming out of the coil wire that you didn't have before it means your points are
bad, and they need to be replaced or cleaned. To clean them, close them up (to
put tension on them) and put a piece of paper between the points. Pull the paper
through a few times. This should remove any oil that has gotten on the points.
Although not recommended you may want to substitute fine sandpaper to clean the
points. If you weren't able to get a spark even after substituting the points
with a screwdriver you'll need to check the condenser.
The last stop along the primary circuit is the condenser. It is a
small cylinder about 3/4 of an inch long, with one little wire coming out of the
top of it. It's usually mounted on the inside of the distributor, but can be
found on the outside of Mallory distributors. Disconnect the wire and hold the
condenser so that it doesn't make contact with any metal. With the points are
still open, touch the movable point and the base plate with a screwdriver as
before. If you get a spark at the screwdriver point you probably have a bad
condenser and need to replace it. A further check can be made with the
multimeter. This time the condenser should be screwed back down so that it's
touching metal but with the little wire still disconnected. Set the meter to the
DC volts scale and measure the voltage from the disconnected small wire to the
screw on the distributor that the wire is normally connected to. If you get any
voltage reading then the condenser is bad and must be replaced.
That's about it for the primary circuit, and most of the time you
should have found the problem. The secondary circuit has fewer components and
usually is not the cause for starting problems.
In order to check the secondary circuit the primary circuit needs to
be functioning correctly. The check of the secondary circuit for the most part
is done by visual inspection. Since there are only a few things to check in the
secondary circuit it should go fairly quickly. Start by examining the condition
of the spark plug wires. If they are greasy or wet, dry them off. If they are
brittle or cracked, replace them. To check the internal condition of the wires
you will need a multimeter. Connect one lead to each end of the wire and set the
multimeter to the ohms scale. What you are going to do is measure the resistance
of the wire. You should get a reading of about 8000 to 10,000 ohms per foot.
Twist and bend the wire a little while watching the meter. If the reading drops
to zero, the wire has a break in it and will need replacing. Next remove the
distributor cap and look inside. Make sure there are no carbon tracks inside the
cap. Carbon tracks look like black lightening lines that go between the spark
plug wire terminals inside the cap. These carbon tracks work like a printed
circuit board and conduct electricity, which will short things out. If you find
any, the cap needs replacing as well as the spark plug wires. In a pinch you
might be able to scrape or wash the tracks off to get the car running. Pull the
rotor out of the center of the distributor and sand it down a little and wipe it
off. If it's been raining or is damp outside try spraying WD40 on the wires and
the distributor cap. Even if the wires appear dry, moisture can penetrate.
The Spark Plugs
Although the secondary circuit is pretty reliable the spark plugs do
cause problems. The problem can be as simple as wet plugs from a flooded engine
to bad plugs themselves. I experienced a problem once where I had spark at the
tester so I spent the next several hours tracking down a problem that didn't
exist. The problem was in one spark plug that was bad, and it was enough to keep
the engine from firing. For this reason I would recommend pulling all the plugs,
cleaning them, gaping them and testing them. Before pulling the plugs be sure to
number the wires to correspond with the cylinder that they are attached to. To
test the plugs, reconnect them to the spark plug wires and lay them on top of
the valve cover. Have someone turn the engine over and watch the plugs to make
sure that each one is firing. If you find one plug that isn't sparking, switch
it with the one next to it to make sure it's the plug and not the wire. If you
are turning over the engine using the solenoid make sure the ignition is turned
Well that's about it. It may sound complicated but it really isn't.
If you find yourself stuck on the road somewhere it's either do it yourself or
wait and wait and wait for help. If you keep a few extra parts, some tools, and
a copy of this article, at least you stand a chance of getting back on the road
in a reasonable amount of time.
Speedometer Magnet Weakens
The speedometer in my 1971 MGB was reading quite a bit below my actual speed.
I'd worked out a lot of the other bugs in the car but this was becoming a major
irritation. There wasn't anything mechanically wrong, it just seemed that the
rotating magnet had lost some strength over the years.
I expect most of you have looked inside a common speedometer at some
time. There's a bar magnet, driven by the rotating cable, that spins in an
aluminum cup connected to the pointer indicator. The magnetic fields set up a
drag force on the cup that increases as the spin rate increases. If the magnet
gets weak the indication gets to read low.
Needless to say, my amateurish attempts to remagnetize the motor
merely resulted in demagnetizing it further-at one point it would read no more
than 35 at 60 mph! Most irritating...
Almost despairing I finally checked my old standby, the Radio Shack
catalog. Ah yes, some tiny rare earth button magnets (Cat #64-1895, about $1.50
for two). Maybe they would help, so I bought six. First try I put two on. They
stick themselves to the "wings" of the rotor (I don't know what the
wings are for, maybe to adjust the damping of the movement). Wow, now I had 120
mph indicated at 60!! They are really strong!
Taking one magnet off, I was back in the right ballpark, and from
then on it was just a matter of trial and error to home in on the right
calibration. Installing the magnet at a smaller radius reduces the indication
sensitivity, and vice versa. The magnets are so small that the out of balance
isn't a significant factor.
Now I don't have to go through those "How many revs/per 10
mph?" calculations to check my speed any more. If it says 60-then 60 it is!
Tail Lights: Vibrations Causing
I used to have problems with my Lucas taillight bulbs rotating because of
vibration. This, of course, caused the two contacts to miss, and the taillight
to malfunction. I might add that I own Morgans which, of course, add to the
problem due to the harsh suspension!
At first I tried to bend the 'spring portion' of the contacts and
while bending works well for a while, a couple of good bumps later, you have to
unscrew the lens and re-align the bulb.
My present method lasts until the bulb burns out. I "glue"
the bulb in place! This is not as drastic as it sounds. First, I clean off the
contacts on the bulb and the fixture, insert the bulb and put a very small dab
of silicone rubber/RTV on the side of the bulb where it is inserted in the
tubular section of the assembly. This eliminates all rotation and is unaffected
by the heat from the bulb. When it comes time to renew the bulb, just twist a
little harder than normal and the very small amount of silicone rubber gives
The above technique can prevent unnecessary stops by the police for
suspected burnt out taillights and also keep you operational for concours.