The PICKUP COIL OHMETER TEST compares
actual pickup resistance with the manufacturers
specifications. If the resistance is too high or low, the
pickup coil is faulty. To perform this test, connect the
ohmmeter across the output leads of the pickup coil.
Wiggle the wire to the pickup coil and observe the
meterreading. This will assist in locating any breaks in
the wires to the pickup. Also, using a screwdriver,
lightly tap the coil. This action will uncover any break
in the coil windings.
Pickup coil resistance varies between 250 and
1,500 ohms, and you should refer to the service manual
for exact specifications. Any change in the readings
during the pickup coil resistance test indicates the coil
should be replaced. Refer to the manufacturers service
manual for instructions for the removal and
replacement of the pickup coil.
Once the pickup coil has been replaced, it will be
necessary to set the PICKUP COIL AIR GAP. The air
gap is the space between the pickup coil and the trigger
wheel tooth. To obtain an accurate reading, use a NON-
MAGNETIC FEELER GAUGE (plastic or brass).
With one tooth of the trigger wheel pointing at the
pickup coil, slide the correct thickness non-magnetic
feeler gauge between the trigger wheel and the pickup
coil. Move the pickup coil in or out until the correct air
gap is set. Tighten the pickup coil screws and double-
check the air gap setting.
The ignition system must be timed so the sparks
jump across the spark plug gaps at exactly the right
time. Adjusting the distributor on the engine so that the
spark occurs at this correct time is called setting the
ignition timing. The ignition timing is normally set at
idle or a speed specified by the engine manufacturer.
Before measuring engine timing, disconnect and plug
the vacuum advance hose going to the distributor. This
action prevents the vacuum advance from functioning
and upsetting the readings. Adjustment is made by
loosening the distributor hold-down screw and turning
the distributor in its mounting.
Turning the distributor housing against the
distributor shaft rotation ADVANCES THE TIMING.
Turning the distributor housing with shaft rotation
RETARDS THE TIMING. Refer to figure 2-53.
When the ignition timing is TOO ADVANCED,
the engine may suffer from spark knock or ping. When
ignition timing is TOO RETARDED, the engine will
have poor fuel economy and power and will be very
Figure 2-53.Determining the direction of rotor rotation.
sluggish during acceleration. If extremely retarded,
combustion flames blowing out of the open exhaust
valve can overheat the engine and crack the exhaust
A timing light is used to measure ignition timing. It
normally has three leadstwo small leads that connect
to the battery-and one larger lead that connects to the
NUMBER ONE spark plug wire. Depending on the
type of timing light, the large lead may clip around the
plug wire (inductive type), or it may need to be
connected directly to the metal terminal of the plug
wire (conventional type).
Draw a chalk line over the correct timing mark.
This will make it easier to see. The timing marks may
be either on the front cover in harmonic balance of the
engine, or they may be on the engine flywheel.
With the engine running, aim the flashing timing
light at the timing mark and reference pointer. The
flashing timing light will make the mark appear to
stand still. If the timing mark and the pointer do not line
up, turn the distributor in its mounting until the timing
mark and pointer are aligned. Tighten the distributor
Keep your hands and the timing light leads
from the engine fan and belts. The spinning fan
and belts can damage the light or cause serious
After the initial ignition timing, you should check
to see if the automatic advance mechanism is working.
This can be done by keeping the timing light flashes