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My 2003 GMC Sonoma 4

Tiny
LASURVIVOR47
  • MEMBER
  • 2003 GMC SONOMA
  • 120,000 MILES
My 2003 gmc sonoma 4.3 will crank over, but will not start. If I add fuel down the throttle body it will start and then shut off after the fuel is used up. I know I have spark. I cleaned the IAC and the map sensor. I also did a fuel pressure test. The results were 58 psi with ignition on and around 57 psi cranking. When I stopped cranking the engine the pressure stayed at 57 psi for more than 5 minutes. I'm thinking either a leaky fuel regulator, or fuel injectors, or even a vaccume leak? What do you think? Thank you in advance! Paul
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Thursday, December 27th, 2012 AT 4:34 PM

14 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
I'd use a noid lite and check for injector pulse, engine cranking. The autostore sells a noid lite. Check for voltage at the injectors, key on, pink wire. That circuit is fuse protected.
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Thursday, December 27th, 2012 AT 5:08 PM
Tiny
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Ok thank you I will try that. I appreciate your time!
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Thursday, December 27th, 2012 AT 5:13 PM
Tiny
JDL
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No problem. Let us know what you find.
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Thursday, December 27th, 2012 AT 6:50 PM
Tiny
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I used my test light to check for voltage to the spider connector. There are 7 pink wires and all have power. I had someone crank the engine while I tested for a pulse on each wire. I got a pulse for each wire. The noid light doesn't connect to the spider connector. I could smell alot of fuel! I'm thinking fuel regulator is leaking? Thanks!
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Thursday, December 27th, 2012 AT 7:09 PM
Tiny
JDL
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I thought your fuel pressure looked good. Any applicable trouble codes? Check the coolant temp sensor.

Part of the fuel pressure test is to bleed pressure down to 10 psi, monitor the fuel gage for 5 minutes. If pressure drops more than 2 psi, replace the pressure regulator.
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Thursday, December 27th, 2012 AT 7:37 PM
Tiny
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I don't have a scan tool. So I can't check the codes. Can't afford a scan tool right now. I will check the coolant sensor. When I had the fuel pressure tester connected and stopped cranking. The pressure remained at 57 psi and didn't drop. Thanks again!
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Thursday, December 27th, 2012 AT 7:49 PM
Tiny
JDL
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Usually, obd2 code readers don't cost much? I understand money issues. I have the same problem.
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Thursday, December 27th, 2012 AT 8:08 PM
Tiny
LASURVIVOR47
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  • 45 POSTS
Ok my friend I will check that reader out. Thanks!
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Thursday, December 27th, 2012 AT 8:24 PM
Tiny
JDL
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Let us know what you find.
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Tuesday, January 8th, 2013 AT 7:13 PM
Tiny
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I bought the code reader and no codes came up. I re checked the fuel pressure and it was below 50 psi. The first test was higher. So I'm going to change the fuel pump and filter. Thanks for getting back to me. Paul
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Tuesday, January 8th, 2013 AT 11:43 PM
Tiny
JDL
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My info says 55--62 at key on, no crank.
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Wednesday, January 9th, 2013 AT 2:52 PM
Tiny
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I have had the plenium off. I checked the injectors. They were working. I checked the sensors. They seemed fine. Re installed the plemium. Performed another fuel test. It was below 50 psi when cranking. I had heard that under 50 psi the pump was no good. So I have one on order, and I'm changing the fuel filter while I'm at it. If this don't work, it's back to the beginning. Thanks for getting back to me. Paul
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Wednesday, January 9th, 2013 AT 8:18 PM
Tiny
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I hope that fixes your problem.
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Wednesday, January 9th, 2013 AT 9:17 PM
Tiny
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I hope so too! Thanks for getting back to me.I'll let you know what happens. Paul
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Thursday, January 10th, 2013 AT 3:23 AM

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