Jim Grant's Tech Tips
'96 GMC Pick-up, Setting Timing
Q: I need help to set the ignition timing on a '96 GMC Pick-up with a 4.3 liter engine. I had to take the intake off to fix a leak and I cannot get it to start.
A: Times have changed and setting ignition timing is one of those changes. How is that? It is not adjustable, the distributor in your vehicle is fixed and can only be installed one way and that is the correct way only. If you cannot start the vehicle the distributor is likely installed incorrectly. If you do get it started and the check engine light comes on you'll need to check the computer code. If a computer code # P1345 is present the computer has determined that the distributor is incorrectly installed. The computer knows this by comparing the sensor in the distributor, called a camshaft position sensor, to the crankshaft position sensor on the engine. If the two sensor's reference pulses are too far out of range from each other the engine will not start or if it does a check engine light will come on. Once you have the distributor installed correctly you need a computer scan tool to fine tune the distributor's sensor (camshaft) to the crankshaft position sensor. In the engine data display of the scan tool you'll need to find what is called camshaft retard. The camshaft retard indicates the difference between the camshaft position sensor and the crankshaft position sensor in degrees. I like seeing the setting within +or- 2 degrees of zero. Isn't amazing how complex something as simple as replacing a leaking gasket has become?