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8-50
IGNITION SYSTEM
If the secondary lead shows any signs of damage,
the lead should be replaced with a new lead with
the neoprene nipple since the old lead can cause
arcing, and therefore, ruin a new coil.
Ballast Resistor
The ballast resistor is a compensating resistance in
the ignition primary circuit. During low speed opera-
tion, when the primary circuit current flow is
as
high,
the ballast resistor temperature rises, increasing the
resistance. This reduces the current flow, thereby
prolonging ignition contact life. At high speed opera-
tion, when the primary current flow is low, the bal-
last resistance cools off allowing more current flow,
which is required for high speed operation. During
starter operation, the ballast resistor is bypassed, al-
lowing full battery voltage to ignition primary circuit.
IGNITION SYSTEM
8 CYLINDER DISTRIBUTOR
utor contacts and condenser, vehicle frame, and the
primary wiring make up the low voltage primary cir-
cuit. The secondary high voltage circuit includes the
coil secondary winding, the distributor cap and rotor,
the spark plug cables, the spark plugs and the vehi-
cle frame.
Description
The ignition system consists of two separate cir-
cuits. The battery, ammeter, ignition switch, ballast
resistor, primary winding of the ignition coil, distrib-
SERVICE PROCEDURES
SECONDARY CIRCUIT INSPECTION
The coil to distributor cap wire and the spark plug
wires should make good, clean contact in the ignition
coil, the distributor cap towers and on the spark
plugs. Wires that are loose or that are not inserted
all the way into the towers or on the plugs will cor-
rode and increase the resistance as well as cause car-
bon tracking of the coil or cap towers. Make sure
the cap nipples on spark plug covers are in good
condition and that they are tight on the cap towers
and around the plug insulators.
The ignition coil tower,
if
oily or dirty, should be
wiped clean and inspected for cracks, carbon track-
ing or oil leaks. Replace the coil if faulty.
Inspect the distributor cap for oil film, dirt or metal
particles on the inside surface. Any contamination,
however slight, can become conductive and cause
hard starting in wet weather. Thoroughly wash the
cap in a
weak
solution of liquid soap or non-flamable
detergent in warm water. Do not use a concentrated
solution or soak the cap in the solution. Scrub the
inner surfaces with a stiff bristle nylon brush to clean
between the
ribs
and the crevices. Rinse well in hot
water, shake out excess of water and dry thoroughly.
Do not use compressed air to dry or blow out the
water. Carefully inspect for cracks or carbon tracking
on the inner and outer surfaces. Replace the cap if
faulty
.
The secondary cables, cap and rotor should
be
tested, using Tool C-3296. This tester provides high
voltage which is sufficient for testing secondary in-
sulation.
Test the resistance of the spark plug cables. Re-
place the cable
if
resistance is more than
30,000
ohms, or if the terminal has pulled off the cable.
Jerking the wires to disconnect them from the
plugs can stretch them and increase secondary re-
sistance. To remove the wire, grasp the boot at
the end of the wire and rotate the boot slightly to
break the adhesion between it and the spark plug
insulator. Then use a straight pull to remove the
spark plug.
The rotor and distributor cap electrodes should be
inspected for burning. Replace the rotor if the elec-
trode is burned on the top or if the electrode is worn
too short.
DISTRIBUTOR RESISTANCE TEST
This test indicates the resistance of the ignition pri-
mary circuit from the distributor side of the coil,
through the points and the distributor ground. Ex-
cessive resistance in this portion of the ignition sys-
tem will prevent the coil from producing sufficient
output for good over-all ignition. To perform test,
proceed as follows:
(1)
Turn the Selector Switch of a tach-dwell unit
to
the CALIBRATE position and adjust the Dwell Cali-
brator until the Dwell Meter reads on the set line (test
leads separated).
(2)
Leave the selector Switch in the CALIBRATE
position, connect the tach-dwell red lead to the
dis-
tributor terminal of the coil and the black lead to a
good ground.
(3)
Turn the ignition switch "ON." Observe the
dwell meter reading. Meter points should be well
within the black bar marked "DISTRIBUTOR RESIST-
ANCE." If reading is zero or outside of black bar,
crank the engine with the starter until the meter point-
er moves as far to right as possible. (This will indicate
that the contacts are closed.) A reading now within
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