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1995 GMC Jimmy engine won't start

Tiny
JASON9591
  • MEMBER
  • 1995 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 190,000 MILES
I have 95 s-15 jimmy 4.3 cpi it's at repair shop been there about 2 months the problem won't start because fuel injector is not pulsing and not reciving pulse from computer replaced camshaft senor, crank sensor, control module checked all wiring to these all reads good. Tryed 3 different computers one of which I know works. Engine has spark. New fuel pump which reads 68psi at engine this started about six months ago at first it would stall and then start right back up as time went on when it stalled it would take about 5-10 minutes of cranking to get it to start then it wouldn't start at all took to shop they took apart plenium found nothing wrong put it back together started right up about 3 days later it stalled and won't start been in shop they have no clue what is wrong they said they tryed everything checked all grounds, new plugs, wires, cap, rotor, coil, tps senor, egr, cam esenor, crank senor, control module, computer, fuel pump, fuel filter, fuel injector, tryed different distribtor. No engine lights will come on please help
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Monday, March 10th, 2008 AT 5:21 PM

12 Replies

Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
Your fuel pressure is too high. It should be 54-64 psi, no more, no less. Either there is a restriction in return fuel line, or the CPI assy. Is bad Also known a spider. And very common on these motors.
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Monday, March 10th, 2008 AT 5:42 PM
Tiny
JASON9591
  • MEMBER
  • 19 POSTS
Spider is new and it not a question of fuel pressure it why there is no signal coming from the computer to tell it to pulse
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Monday, March 10th, 2008 AT 6:07 PM
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,750 POSTS
So it will run on starter fluid. Your saying it runs fine if sprayed with starter fluid but it has no injector pulse, correct. When you turn the key to run does the check engine light on dash come on? Is there a theft light on the dash that comes on and goes out or does it come on and flash while key is in the run position? We should be able to figure this out. I have seen every possible problem with the trucks, just bare with us we will get it running.
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Monday, March 10th, 2008 AT 6:18 PM
Tiny
JASON9591
  • MEMBER
  • 19 POSTS
Yes it ran with starting fluid and no pulse coming from wire at injector or at computer there is no theft protection engine light comes on like normal than goes out after seconds has been hooked up to computer was no help my mechanic says the truck shoud run but don't he had one of his friend come check it out (he worked for gm) he tryed had no luck everyone I know says they never seen this problem
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Monday, March 10th, 2008 AT 6:33 PM
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,750 POSTS
You said you replaced the computer, correct. Did you get them from gm and have iff board programming done? This is very important. Or did you install computer from a running vehicle.
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Monday, March 10th, 2008 AT 6:40 PM
Tiny
JASON9591
  • MEMBER
  • 19 POSTS
At first I tryed a used computer which was from the same year truck and the program codes where the same that didn't work so I bought one and had programed at dealer and still no luck we also replaced the cam, and crank senors multiple times same with the control module. The wiring between these componets was also checked multiple times
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Monday, March 10th, 2008 AT 6:51 PM
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,750 POSTS
Wow. It looks like you have everything covered. Lets go over evrything that will cause to have spark but no injector pulse. Bad pcm(we know is good) tps voltage at 4.5v or higher at start up? This will cause a clear flood condition and no injector pulse. Manifold absolute pressure sensor reading less than 3 volts on start up? A shorted fuel tank pressure sensor on fuel tank(for emissions) will bring down map voltage causing no inj pulse. One injector ground trigger wire from vcm to injector that is shorted to ground will cause no inj pulse( but that would also cause loss of fuel pressure. A shorted fuel injector would cause no pulse but we know that is good. Can your mechanic read data from the computer during all this? What does o2 sensor voltage read? White wire from ignition module to the vcm being shorted or open, this signal tells pcm when to fire injectors. This is every possible thing I can see to cause no inj pulse on a truck that has spark. I hope this helps
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Monday, March 10th, 2008 AT 7:10 PM
Tiny
JASON9591
  • MEMBER
  • 19 POSTS
Thanks for the help i'll try all of the following you said hope it works let you know tomorrow
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Monday, March 10th, 2008 AT 7:24 PM
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,750 POSTS
Just reply to this post and we will see it. Good luck
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Monday, March 10th, 2008 AT 7:26 PM
Tiny
JASON9591
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Had no luck my mechanic tried everything you said do you have any other ideas?

My mechanic gave up has no other ideas it's now going to the chevy dealer
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Thursday, March 13th, 2008 AT 8:59 PM
Tiny
JASON9591
  • MEMBER
  • 19 POSTS
After taking this truck two 2 different shops the second shop spent 8hrs in time they found that the coil was bad put new one in run for couple of days then wouldn't start again so I started playing with the wires sure enought the wiring harness going to cranlshaft sensor was bad if I shook it everything started to turn of and on put new harness on runs like a champ. The harness must of shorted the new coil I had in it. It took two different shops 28hrs in time and they still couldn't figure it out shows how much they know. Don't ever trust a mechanic.
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Tuesday, April 29th, 2008 AT 8:41 PM
Tiny
SERVICE WRITER
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Jason. Easy on the trust thing. Do you know how hard it is to nail something like that down. That is a rare bird. There were several of us looking at this and got stonewalled. Hats off to the shop that had the believe to go into a different direction.

Aggraivated with it. You bet. But The "trust" comment really doesn't apply from what I'm seeing.

Just my 2 cents.
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Tuesday, April 29th, 2008 AT 8:52 PM

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