99 GMC cranks and fires almost starts when you turn the key off.

  • 1999 GMC SIERRA
  • 80,000 MILES
Gmc 4 wheel drive sat for 2 months. The battery went dead. I tried to jump it and it wants to start. Put a new battery in it and acts the same. Ran good when it was parked. It is a six cyl. Stick.I believe it is getting gas and spark. It has never been tuned because it always ran so well.I check fuses and banged on the gas tank with a rubber hammer. Ground strap is connected.
Do you
have the same problem?
Saturday, October 22nd, 2011 AT 2:49 PM

1 Reply


Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, Do you hear the fuel pump come On when you turn key on? If not check fuel pump fuse and fuel pump relay if okay-check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,cap and rotor,distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing

If both fuel and spark is present-check the valve and ignition timing, this will lead you to problems

with compression and valves opening and closing at the wrong time/broken or jumped timing

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Wednesday, October 26th, 2011 AT 5:25 AM

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