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Engine not starting up?

Tiny
CLIFF ARTHUR
  • MEMBER
  • 1994 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 92,000 MILES
Always cranks but occasionally does not start. Starting fluid does not help as there is no spark at those times. Have removed ignition module and had it tested. Both AutoZone and Napa tested module and say it is okay. Tested coil resistance and both circuits are in spec. The factory tachometer lead comes from the coil but the tachometer is not accurate or even close when engine chooses to start and run. Is there another test for coil/tachometer pick up? Tachometer problem came up at same time as the starting problem.
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Monday, July 23rd, 2018 AT 2:32 PM

13 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi and thanks for using 2CarPros.com.

When you turn the key to the on position without cranking the engine over can you hear the fuel pump run in the tank for 5 seconds?

https://www.2carpros.com/articles/car-cranks-but-wont-start

Please run down this guide and report back.
It sounds like you have done your homework and checked what needed checked. However, have you determined if there are trouble codes stored in the computer? This vehicle has an OBD 1 system and it is really easy to check.

The OBD1 port is under the dash. Jump A and B (see picture) with a paper clip. key on engine off. All codes are 2 digits. Code will first flash. The check engine light will blink once, delay, and then twice in rapid succession. One flash delay then two flashes = code 12. This system will display the same code three consecutive times. After the 12, any trouble codes stored in the computer will flash.

I have attached a picture of the OBD port for you to see. Additionally, go to this link to identify all GM OBD Trouble codes.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

I hope you find this helpful. Let me know if you have other questions and what you find.

Take care,
Joe
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Monday, July 23rd, 2018 AT 8:31 PM
Tiny
CLIFF ARTHUR
  • MEMBER
  • 8 POSTS
Thanks for information on OBD 1. I jumped terminals A and B but no new codes showed up. (Battery was replaced two weeks ago and truck has not been driven much since then so not much time to acquire new codes) Check engine light has not been on before or after battery replacement.
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Wednesday, July 25th, 2018 AT 5:31 AM
Tiny
CLIFF ARTHUR
  • MEMBER
  • 8 POSTS
Any other thoughts?
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Wednesday, July 25th, 2018 AT 1:21 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Welcome back. I have to be honest, either it is related to the module (showing good but going bad) or it is in the distributor itself. Do you have access to a known good ICM? I have a feeling it is going bad.
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Thursday, July 26th, 2018 AT 7:35 PM
Tiny
CLIFF ARTHUR
  • MEMBER
  • 8 POSTS
This morning I was undecided about how to proceed. I did not want to pull the distributor if I did not have to. So I ordered a new coil and ICM. I will let you know once they are installed.
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Thursday, July 26th, 2018 AT 8:19 PM
Tiny
CLIFF ARTHUR
  • MEMBER
  • 8 POSTS
Installed both OEM coil and OEM ICM. It started up and ran well for about three miles on test drive, allowing me to get almost home. It shut off while slowing for a turn and coasted to a stop. Would not restart and had no spark. Tried to restart several time over the next 24 hours with no luck. Then this morning it started right up and I drove it the remaining half mile home. Suggestions?
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Thursday, August 2nd, 2018 AT 7:03 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,665 POSTS
When the ignition spark stops and the key is on do you have power on both sides of the coil? (Not cranking over.)
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Sunday, August 5th, 2018 AT 6:12 PM
Tiny
CLIFF ARTHUR
  • MEMBER
  • 8 POSTS
It has started and run okay for the last five starts. (I do not want to risk having to tow it so I have not left the driveway). Will check the coil on the next "no spark" and let you know.
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Tuesday, August 7th, 2018 AT 7:05 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,665 POSTS
Please do, we are interested to see what the problem is.
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Tuesday, August 7th, 2018 AT 10:21 AM
Tiny
CLIFF ARTHUR
  • MEMBER
  • 8 POSTS
The truck started again so I let it run for about twenty minutes and it then stalled. So now I have the "cranks but will not start and no spark" condition. The two wires from the ICM to the coil show no voltage with the key on. Of the other two wires connected to the coil, one shows 12.18 volts with the key on. The pattern seems to be that it runs until it gets warm, stalls, and then wont start again until about twenty four hours later.
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Tuesday, August 7th, 2018 AT 1:24 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,665 POSTS
This sounds like the engine coolant temperature sensor is shorting out causing the PCM to cut the ignition control. I have seen this problem before. Here is a guide to help you see what you are in for when doing the job and the location of the sensor for your truck:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken
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Wednesday, August 8th, 2018 AT 10:23 AM
Tiny
CLIFF ARTHUR
  • MEMBER
  • 8 POSTS
Installed new coolant temperature sensor. Started and ran for about fifteen minutes, made a clunk like noise from under hood and stalled. Now have "no start no spark" condition again.
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Thursday, August 9th, 2018 AT 8:32 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,665 POSTS
Does it crank over okay sounds normal can you make a video and upload it here in your response? I can hear if the engine has a mechanical issue. If the engine is okay lets test the wiring because it sounds like the PCM could be the problem. Here is a guide to help us check the wiring and the engine wiring diagrams so we can see how the system works. Check all power and grounds if everything checks out try a used PCM. Here is the location:

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

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken
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Friday, August 10th, 2018 AT 10:28 AM

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