Service Precautions; Distributor Replacement - GMC G Service Manual

IGNITION SYSTEM ON-VEHICLE SERVICE

SERVICE PRECAUTIONS

Some service tachometers and electronic diagnostic
equipment may NOT be compatible with these ignition sys­
tems. Consult your tool representative to update your
equipment for compatibility with these systems.
1. When making compression checks, disconnect the
engine control switch feed wire at the distributor.
When disconnecting this connector, release the lock­
ing tab while pulling downward on the connector
body; do not use a screwdriver or tool to release the
locking tab as it may break the tab.
2. No periodic lubrication is required. Engine oil lubri­
cates the lower bushing and an oil-filled reservoir pro­
vides lubrication for the upper bushing.
NOTICE: The tachometer terminal must NEVER
be allowed to touch ground, as damage to the
module and/or ignition coil can result.
3. On integral coil distributors, the tachometer (TACH)
terminal is next to the engine control switch (BAT)
connector on the distributor cap. On distributors with
separate coils, the TACH terminal is located at the
coil (figure 44).
4. There is no dwell adjustment since this is controlled
by the module.
5. The material used to construct the spark plug wires is
very soft but will withstand more heat and carry a
higher voltage. Due to the more pliable wire, scuffing
and cutting become more likely. Route the spark plug
wires correctly to prevent chafing or cutting. When
removing a spark plug wire from a spark plug, twist
the boot where it seats onto the spark plug, then pull
on the boot to remove the wire.

DISTRIBUTOR REPLACEMENT

Some components, such as the engine cover or air
cleaner, may need to be removed to reach the distributor.
DISTRIBUTOR WITH INTEGRAL COIL
M Remove or Disconnect
1. Engine control switch battery feed wire from the dis­
tributor cap.
2. Tachometer lead (if equipped) from the cap.
3. Ignition coil connector from the cap.
• Do not use a screwdriver or tool to release the
locking tabs.
4. Distributor cap by pressing down on the four spring-
loaded screws and turning the latches to the left.
5. Vacuum hose from the vacuum advance unit (if
equipped).
6. Distributor clamp bolt and hold-down clamp from the
engine.
ENGINE ELECTRICAL 6D-43
• Note the position of the rotor, then pull the dis­
tributor up until the rotor just stops turning to the
left. Again note the position of the rotor.
7. Distributor.
H Install or Connect
To ensure correct timing of the distributor it must be
installed with the rotor correctly positioned. Refer to step 6
of the removal procedure.
If the engine was accidentally cranked after the distribu­
tor was removed, the following procedure can be used for
installation:
• Remove the number 1 spark plug.
• Place finger over the number 1 spark plug hole
and crank the engine slowly until compression
is felt.
• Align the timing mark on the pulley to "0" on the
engine timing pointer.
• Turn the rotor to point between number
number 8 spark plug towers on the distributor
cap on V8 engines and between number 1 and
number 6 on 6 cylinder engines.
1. Distributor.
• If the distributor shaft won't drop into the engine,
first insert a screwdriver into the hole for the
distributor and turn the oil pump drive shaft.
2. Distributor hold-down clamp and clamp bolt.
3. Vacuum hose to the vacuum unit (if equipped).
4. Cap on the distributor.
• The aligning tab on the cap should engage with
the notch in the housing.
5. Four hold-down spring latches.
6. Ignition coil connector to the cap.
7. Engine control switch battery feed wire.
8. Tachometer lead (if equipped).
• Set ignition timing. Refer to "Ignition Timing" in this
section.
DISTRIBUTOR WITH SEPARATE COIL
E
Remove or Disconnect
1. Negative battery cable.
2. Wiring harness connectors at the side of the distribu­
tor cap.
3. Distributor cap; move it out of the way.
• Scribe a mark on the engine in line with the
rotor.
• Note the position of the distributor housing in
relation to the engine.
4. Distributor hold-down nut and clamp.
5. Distributor.
and
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