My 1996 GMC 1500 with 160,000 miles is not wanting to start. The electric fuel pump is functioning with good pressure at the fuel rail. The engine just cranks but will not fire. When I stop cranking it chortles/pops and tries to make a couple of turns backwards. There is a spark at the plugs (although it doesn't appear to be the strongest). Spraying fuel directly into the trottle body while cranking does not help. After multiple attempts it does eventually start (a warmer day seems to help) and once it has started and warmed up it drives, stops and restarts completely normally. I recently changed the intake manifold because the coolant ports were badly corroded. Any thoughts on causes would be appreciated.
1996 GMC starting problems
- Thread starter stevo
- Start date
Molson02536
New member
Inspect your wire leads to the coil and the inspect your ICM and wire leads to the ICM under the distributor cap. You mentioned you did some intake manifold, wondering if your timing is off on your distributor.
The Vortec engines can not be "timed" in the way you are used too. The distibutor housing holds the cam sensor, The PCM calculates the timing by measuring the crank signal and the cam signal. What you are seting by turning the distibutor housing is the correlation between the 2 sensors.
On the V-6 model, the housing holddown bracket is fixed to the housing so if you return the rotor to the proper position when reinstalling the housing, the engine should be at the correct cam sensor position setting.
Believe me I have seen them installed incorrectly. To set the correlation between the 2, you will need a scan tool that can read camshaft position offset. With the engine RPM over 1200 adjust the offset too 0 degrees.
This is fine for a new engine but a non adjustable disributor on an older engine, I think would cause some trouble. The timing chain stretches, the disributor shaft wears, gear wear causes the timing "correlation" to slowly drift. I just checked a v-6 with 200,000 on it and the cam retard was off -16 degrees.
TEST PROCEDURE
The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following:
With the ignition OFF, install a scan tool to the DLC.
Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM.
Increase engine speed to 1000 RPM.
Monitor the Cam Retard Offset.
If the Cam Retard indicates a value of 0°+/-2°, the distributor is properly adjusted.
If the Cam Retard does not indicate 0°+/-2°, the distributor must be adjusted.
ADJUSTING PROCEDURE
With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM.
Start the engine and raise engine speed to 1000 RPM.
Using a scan tool monitor Cam Retard Offset.
Rotate the distributor as follows:
4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction.
4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction.
Repeat step 4 until 0°+/-2°, is obtained.
Turn the ignition OFF.
Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.).
Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset
Good luck and recheck your timing.
Molson02536
New member
If this happens again try putting a distributor cap with brass contacts, helps on the 4.3 with misfires. I used to have that problem then i upgraded my ignition with ACCEL 130141 Heavy Duty Rotor, ACCEL 120142 Distributor Cap, and MSD Ignition 8231 Blaster Replacement Coil for the 4.3 Vortec. Not sure what Rotor and Cap part numbers are for your Sierra, but i think the Coil is the same on the 4.3 V6 and the V8 vortec.
I used to have issues with my 1996 Jimmy also and just upgraded the ignition system and seams to run like a charm.
Glad to see you got your Sierra running 100% again, be safe and feel free to ask any more questions if there are any more issues.
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