1996 GMC Jimmy Backfiring No Start

PUNKUR67

MEMBER
1 POST

I have a 96 gmc jimmy 4wd with a 4.3. The truck has had a hard time starting every once in a while but ran fine after started. My girlfriend tried to start it the other day and it was backfiring and broke the nose of the starter off. Has new plugs, cap, rotor, fuel filter, and air filter. the distributor has not spun and the rotor spins when the motor is turned over. Seems like a timing chain to me but wanted to make shure before i start tearing it apart. Is there an easy way to check the chain on this motor?

Nov 29, 2006 at 10:24 AM

BACKYARDMECHANIC

✓Experienced Mechanic
337 POSTS

Sounds like you are right to think its the chain and I don't blame you for wanting to make sure. Since you car has a distributor it's not that hard.
1) remove the # 1 plug from the head.
2) have an assistant turn the key while you place your finger over the plug hole(just tap the key) .As you start to feel pressure build up with your finger stop.( you are now on the compression stroke)You now have to turn the motor by hand untill the timing mark on the harmonic balancer lines up with the mark on the block. You should be a top dead center
3) Remove the cap and take notice where the rotor is pointing toward. It should be pointing toward the number 1 tower of the distributor cap. If its way off then the chain has stretched or gears are worn and needs to be replaced. Hope this helps
Backyardmechanic :(

Dec 12, 2006 at 1:38 AM

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Suggested Repair

Bring the engine to top dead center on the compression stroke and check that the distributor rotor points to the number 1 cap tower. If it is far off, replace the stretched timing chain or worn gears.

Conversation Summary

The owner of a 1996 GMC Jimmy 4.3 reports occasional hard starting, followed by backfiring that broke the starter nose. Plugs, cap, rotor, fuel filter, and air filter were already replaced, and the rotor still turns while cranking. The expert recommends a compression-stroke TDC check and says a rotor that does not point to the number 1 tower indicates a worn timing chain or gears that need replacement.

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1996 GMC Jimmy Backfiring No Start

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