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11-09-2009, 03:50 PM
| #1 |
| Full Member Join Date: Nov 2009
Posts: 10
 | 99 gmc c6500 misfire I am working on a 99 GMC C6500 with 7.4L engine. Cylinders 5 and 7 are misfiring. I have replaced plugs, wires and those 2 coils. I have spark at the plugs. What else can cause a miss in those 2 cylinders? Compression is 140 psi. |
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11-09-2009, 04:33 PM
| #2 |
| Senior Member  Join Date: Jul 2009 Location: Fredericksburg, VA
Posts: 3,876
 | clogged injectors?
__________________ If the guys who design 'em had to take one home, use it every day for 2 years, and do all the maint and repairs themselves, cars would have a button on the dash to change the oil, filters & plugs. |
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11-10-2009, 04:41 PM
| #3 |
| Senior Member  Join Date: Mar 2008 Location: N.Y.
Posts: 4,932
| check the injector circuit in the fuse box and make sure there is a fuse and not a circuit breaker in it's slot
__________________ 4 wheels move the body 2 wheels move the soul B.W.A.I |
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11-10-2009, 05:29 PM
| #4 |
| Full Member Join Date: Nov 2009
Posts: 10
| Just to be clear, only 2 cylinders are missing--#5 & #7, they are next to each other. Where are the injectors? |
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11-11-2009, 05:47 AM
| #5 |
| Senior Member  Join Date: Oct 2005 Location: Birmingham, AL
Posts: 895
| run a comression check, you could have a blown head gasket
__________________ None of the secrets of success will work unless you do. |
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11-11-2009, 06:08 AM
| #6 | |
| Senior Member Join Date: Mar 2008 Location: N.Y.
Posts: 4,932
| Quote:
__________________ 4 wheels move the body 2 wheels move the soul B.W.A.I | |
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11-11-2009, 11:46 AM
| #7 | |
| Senior Member Join Date: Jul 2009 Location: Fredericksburg, VA
Posts: 3,876
| Quote:
Blown gasket was my immediate thought too, but not with compression like that.
__________________ If the guys who design 'em had to take one home, use it every day for 2 years, and do all the maint and repairs themselves, cars would have a button on the dash to change the oil, filters & plugs. | |
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11-11-2009, 12:09 PM
| #8 |
| Full Member Join Date: Nov 2009
Posts: 10
| The reason I asked where the injectors are is because I don't see a fuel line along the intake manifold with injectors pushed into the manifold. Does this year and model have a fuel manifold at the rear of the engine? If so, how does that work? Could the manifold have 2 lines plugged? I heard that back in the mid-90's GM used such a thing on the Astro van, and that they had problems; did they use it in other applications as well? |
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11-11-2009, 04:30 PM
| #9 |
| Senior Member Join Date: Mar 2008 Location: N.Y.
Posts: 4,932
| wait a minuter, 99 wasn't that throttle body injection?
__________________ 4 wheels move the body 2 wheels move the soul B.W.A.I |
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11-11-2009, 04:39 PM
| #10 |
| Senior Member Join Date: Mar 2008 Location: N.Y.
Posts: 4,932
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__________________ 4 wheels move the body 2 wheels move the soul B.W.A.I |
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