Ignition Timing - GMC G Service Manual

6D-44 ENGINE ELECTRICAL
M Install or Connect
• To ensure correct timing of the distributor, it must be
installed with the rotor correctly positioned. Refer to
Step 3 of the removal procedure.
• If the distributor shaft won't drop into the engine,
insert a screwdriver into the hole for the distributor
and turn the oil pump driveshaft.
1. Distributor.
2. Hold-down nut and clamp.
3. Distributor cap.
4. Wiring harness connector at the side of the cap.
5. Negative battery cable.
COIL REPLACEMENT
H Remove or Disconnect
1. Negative battery cable.
2. Engine control switch and tachometer connectors at
the coil.
3. Coil to distributor lead at the coil.
4. Nuts holding the coil bracket and coil to the engine
bracket.
5. Coil bracket and coil.
• Drill and punch out the two rivets holding the
coil to the bracket.
6. Coil from bracket.
M Install or Connect
1. Coil to the bracket with two screws.
2. Coil bracket to the engine bracket with studs and
nuts.
3. Coil to the distributor lead at the coil.
4. Engine control switch and tachometer connectors to
the coil.
5. Negative battery cable.

IGNITION TIMING

1. Refer to the Vehicle Emissions Control Information
label located on the radiator support. Follow all
instructions on the label.
2. Refer to the Fuel and Emissions Service Manual for
timing information for engines equipped with TBI.
3. With the engine control switch off, connect the pick­
up lead of a timing light to the number 1 spark plug.
On engines with the timing pointer mounted at the oil
pan, use the number 8 (or number 5) spark plug.
Connect a jumper lead between the wire and plug or
use an inductive type pick-up. DO NOT pierce the
wire or attempt to insert a wire between the boot and
the wire. Connect the timing light power leads accord­
ing to the manufacturer's instructions.
4. Disconnect the vacuum hose from the distributor if so
equipped.
5. Start the engine and aim the timing light at the timing
mark (figures 52 and 53). The line on the balancer or
pulley will line up at the timing mark. If a change is
necessary, loosen the distributor hold-down clamp
bolt at the base of the distributor. While observing the
mark with the timing light, slowly rotate the distributor
until the line indicates the correct timing. Tighten the
hold-down bolt, and re-check the timing.
6. Turn off the engine and remove the timing light.
Reconnect the test spark plug wire, if removed.
7. Connect the vacuum hose to the distributor (if
equipped).