Cranks will not start

Tiny
WEAVERISU
  • MEMBER
  • 1995 GMC SONOMA
  • 4.3L
  • V6
  • 2WD
  • MANUAL
  • 194,000 MILES
My truck let me sit yesterday so we towed it to a place I can work on it. We started diagnosing the problems it had. We had no spark or fuel, I replaced the coil and it starts on starting fluid now but the injectors aren't giving any fuel. We went over the fuel system and the pump does pump fuel then entire way to the TBI injectors. We replaced the injectors with new ones and still no luck. We confirmed we have power to the injectors with a test light but the injectors aren't receiving the signal to fire. We aren't sure why. I was hoping someone would have an idea of why?
Sunday, May 31st, 2020 AT 8:22 AM

9 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good afternoon,

If the truck runs with the system primed, then toy have spark and the ignition module is working.

That is what sends a signal to the ECM for firing the injectors.

It is either the ECM or wiring to the ECM.

I attached a wiring daigram of the injectors for you. You need to go to the ECM and test for power to the wires I circled with the key in the on position.

https://www.2carpros.com/articles/how-to-check-wiring

Did you verify the actual fuel pressure? This needs to be done as well.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Roy

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Sunday, May 31st, 2020 AT 2:46 PM
Tiny
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I have not verified fuel pressure as of yet but I have verified that there is no pulse on the injectors to fire them. Going to try and replace the ignition control module and see if that helps.
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Sunday, May 31st, 2020 AT 3:28 PM
Tiny
ASEMASTER6371
  • MECHANIC
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If you have spark, then the module is good. You said you primed it and it runs. That tells me the module is not the issue.

Roy
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Sunday, May 31st, 2020 AT 3:31 PM
Tiny
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No it doesn't run, the injectors don't spray fuel. It will run if we spray starting fluid in it. I was told that the ignition module sends a signal to the ECM to tell it when to fire the injectors.
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Sunday, May 31st, 2020 AT 3:33 PM
Tiny
ASEMASTER6371
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You do not understand what I was saying.

When you primed it with fuel, the engine started and ran until the fuel was burned and shut down. It would not run like that if the module is bad. There would be no spark to burn the fuel.

Yes, the module sends a signal to the ECM that the engine is turning and to flow fuel to the motor.

You can try a module but I doubt it will work. I do not want to see you spend money on a part that will not help you. Whoever told you that information is not familiar with how the system works.

Roy
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Monday, June 1st, 2020 AT 3:29 AM
Tiny
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I went against your advice and put in a new ignition control module and the truck started right up on its own.
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Monday, June 1st, 2020 AT 11:07 AM
Tiny
ASEMASTER6371
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That does not make sense at all.

Glad it fixed it for you.

Roy
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Monday, June 1st, 2020 AT 11:37 AM
Tiny
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I think what happened was part of it died, it was a cheap unit from a brand I never heard of and the previous owner said it was replaced 5 years ago.
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Monday, June 1st, 2020 AT 11:41 AM
Tiny
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Could be. Just glad it is fixed for you.

Roy
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Monday, June 1st, 2020 AT 11:43 AM

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