As the engine in your 1989 Chevrolet pick-up wears, minor changes in the ignition timing can occur. Timing chain and distributor gear wear both contribute to these changes, requiring the ignition timing to be adjusted during the tune-up procedure. When setting the ignition timing, the on-board computer must be put into base timing mode, before adjustments are made to prevent inaccurate timing. This maintenance procedure is well within the average home mechanics ability and requires mostly basic hand tools. A timing light is necessary to read the timing and these are available at your local auto parts store.
Tools Used: Wrench set, Timing light, Parts cleaner, Shop rags, White crayon
Set Ignition Timing
Locate the timing tab on the front of the timing chain cover just above the harmonic balancer, and the timing mark (a groove) on the harmonic balancer. Clean these with parts cleaner spray, and wipe them dry with a shop rag. They can sometimes be covered in sludge build up, and require several attempts at cleaning. Mark the timing mark on the harmonic balancer with the white crayon, and mark the 0 degrees mark on the timing tab, also with the white crayon.
Start the engine and run it at high idle until the coolant temperature reaches normal operation temperature on the dash gauge. Turn off the engine and disconnect the timing connector. The timing connector on the C and K series trucks is located on the passenger side of the firewall breaking out of the main wiring harness and is a single wire connector with a tan wire with a black stripe.
Connect the timing light to the battery. The red cable goes to the positive post, and the black cable goes to the negative post. Attach the timing pick-up to the number one spark plug wire. Number one is the front plug on the drivers side. Start the engine, and aim the light at the timing marks while pulling the trigger on the light. The timing on the 89 Chevrolet truck is 0 degress with the timing connector disconnected. If the two timing marks you marked with white crayon do not line up, adjust the timing.
Set the timing by loosening the distributor slightly, and turning the distributor while observing the timing marks. When they line up, tighten the distributor. Turn off the engine and reconnect the timing connector, remove the timing light, and test drive to verify the repair.
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