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8-42
IGNITION SYSTEM
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 the spark plugs.
Wires that are loose or are not inserted all the way
into the towers or on the plugs will corrode and in-
crease the resistance as well as cause carbon tracking
of the coil or cap towers.
Make sure the spark plug covers are in good con-
dition and that they are tight on the cap towers and
around the spark plug insulators. Snap the plug cov-
ers into the cylinder head wells
so that the lip of the
cover is tight against the cylinder head. Always use
neoprene insulating nipples.
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 conducting and cause
hard starting in wet weather. Thoroughly wash the
cap in a
weak
solution of liquid soap or non flammable
detergent in warm water. Do not use a concentrated
solution or soak the cap in the solution. Scrub the in-
ner surfaces with a stiff bristle nylon brush to clean
between the ribs and the crevices. Rinse well in hot
water, shake out excess 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 or outer surfaces. Replace the cap if faulty.
Old, cracked or damaged wires should be replaced.
The secondary cables, cap and rotor should be tested,
using Tool C-3296. This tester provides high voltage
which is sufficient for testing secondary insulation.
Test the resistance type wire for an open circuit,
loose terminals or high resistance. Replace the cable
if
resistance is more than 30,000 ohms, or
if
the
terminal has pulled off the cable.
NOTE: Jerking the wires to disconnect them
from the plugs can stretch them and increase sec-
ondary resistance. 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 from the spark plug.
Resistor type wire is identified by the word "Radio"
stamped on the insulating jacket. No additional re-
sistors are necessary.
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
electrode is worn too
short.
DISTRIBUTOR RESISTANCE TEST
This test indicates the resistance of the ignition
primary circuit from the distributor side of the coil,
through the contacts 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 overall 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
distributor terminal of the coil and the black lead
to a good ground.
(3) Turn the ignition switch "ON." Observe dwell
meter reading. The meter pointer should be well with-
in the black bar marked "DISTRIBUTOR RESIST-
ANCE.' 'If the reading is zero or outside of black bar,
crank the engine with the starter until the meter
pointer moves as f a r to the right as possible. (This
will indicate that contacts are closed.) A reading now
within the black bar indicates
a normal distributor
primary circuit.
If the reading is outside the black bar, high resist-
ance is present in the distributor primary circuit.
(4)
Remove the test lead from the distributor ter-
minal of the coil and connect to the following points:
(a) Distributor primary terminal (outside)
(b) Distributor primary terminal (inside)
(c) Contact terminal bracket (insulated bracket)
(d) Ground side of the contacts.
(e) Distributor housing.
(5) Repeat the test at each connection until a no-
ticeable change occurs in the meter reading. If a poor
connection or faulty lead is indicated, clean, tighten
or replace as necessary and repeat test
(3).
If faulty contacts are indicated, remove the dis-
tributor for complete inspection, service, testing and
calibration.
IDLE RPM TEST
The engine idle rpm setting should be tested and
recorded as it is when the vehicle is first brought into
the shop for testing. This will assist in diagnosing
complaints of engine stalling or complaints of creep-
ing and hard shifting on vehicles equipped with au-
tomatic transmissions.
Test procedures are as follows:
(1) Turn the Selector Switch to the CALIBRATE
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