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Crank no start problem?

Tiny
LOUD PELLETIER
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 8.1L
  • V8
  • 4WD
  • AUTOMATIC
  • 155,000 MILES
Hello, I have an 8.1 vortex with crank no start problem here’s the result of all my diagnostic.

Have 62 psi of fuel
Getting strong spark
12v at the injector
All fuse and relay are tested and are fine
Crank replaced cam replaced MAF replaced are tested and are okay.

The point is I’m not getting ground pulse to the injector and if I test with my multimeter directly on the injector connector sometime 0v or 6v on all injector but something weird happen it’s been like 3 month since I have tried to started and I notice that the cluster wasn’t show the mileage and my interior mostly disassembled (cause it’s a project truck but before send it to paint shop I want all work perfectly to when I’ll reassemble the truck after the paint )and I see the 3 wire connector on top of the ignition switch and I unplugged et plug back in the mileage comeback and before that the vats system has already been disabled I’ve already with a security problem and I know that’s not the case now and seriously I do not think it’s PCM cause I know a PCM on those truck last the life of the truck.
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Friday, March 17th, 2023 AT 6:10 AM

16 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,756 POSTS
Will the engine run on starting fluid? Also, are the injectors getting a pulse? Is the security light flashing when you try to crank it over? Also how does the engine sound when cranking it over? Can you upload a short video of the engine cranking so I can tell if the engine is hurt or not?

Here is a guide to help you check for the injector pulse:

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

This guide may help as well:

https://www.2carpros.com/articles/car-not-running-advanced

Please go over these guides and report back.
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Friday, March 17th, 2023 AT 10:37 AM
Tiny
LOUD PELLETIER
  • MEMBER
  • 39 POSTS
As I already say, the engine crank is fine, no mechanical problem, the compression is perfect. No security light and yes on starting fluid the engine run fine, and the injector doesn’t receive a ground pulse.
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Tuesday, March 21st, 2023 AT 9:18 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,756 POSTS
It sounds like the PCM is bad, but we should check the grounds first. here is a guide to help and the PCM wiring diagrams so you can see which wires to test:

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

If the grounds check out you can get and if the fuses are okay (test with ignition on) I have left the location and instructions on how to change out the PCM, you can get a preprogrammed unit by searching Google or Ebay. Also, you should unplug all injectors to see if the pulse comes back because a shorted injector can shut down the PCM injector driver.
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Wednesday, March 22nd, 2023 AT 1:58 PM
Tiny
LOUD PELLETIER
  • MEMBER
  • 39 POSTS
I asked to some experienced mechanic in those Silverado model and the common answer a bad power to PCM can cause the PCM to give only 6v to injector and for the they are all tested fine.
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Sunday, March 26th, 2023 AT 1:21 PM
Tiny
KEN L
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Okay, I have the wiring diagrams above lets use this guide to check the voltage and the main power inlets at the PCM.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go over this guide and report back. Also I would check the PCM grounds that can cause a low voltage issue as well.
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Monday, March 27th, 2023 AT 12:16 PM
Tiny
LOUD PELLETIER
  • MEMBER
  • 39 POSTS
I’ll check if the PCM receive 12v at each b+ pin on PCM and the ground but last fall I shake the under-hood fuse box unplug and plug the ign relay and the engine start right up two weeks after crank no start.
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Tuesday, March 28th, 2023 AT 12:04 PM
Tiny
LOUD PELLETIER
  • MEMBER
  • 39 POSTS
And I really the truck running tell to all mechanic on this platform. Thank you
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Tuesday, March 28th, 2023 AT 12:04 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,756 POSTS
Can you elaborate? I am not sure what you were saying on your last post? You may have a shorted injector which will shut down the drivers inside the PCM try unplugging them to see if the injector pulse comes back and if so, plug them in one at a time until the pulse stops this will be the shorted injector, or you can test each injector.

Here is a guide to help:

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Please go over this guide and report back.
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Thursday, March 30th, 2023 AT 12:36 PM
Tiny
LOUD PELLETIER
  • MEMBER
  • 39 POSTS
I took the injector off a working 8.1 daily, so injector is good.
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Friday, March 31st, 2023 AT 9:50 AM
Tiny
KEN L
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If the PCM is getting power and ground and there is no shorted injector I would try a rebuilt PCM.
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Sunday, April 2nd, 2023 AT 9:37 AM
Tiny
LOUD PELLETIER
  • MEMBER
  • 39 POSTS
Okay, update now the engine give spark once in a while still no injector pulse and it seems to receive all 12v it needs to the PCM to work and ground are good too. Yesterday I tried to start it with some quick start and even with quick start it doesn’t start 2 months ago the spark was consistent.
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Friday, May 5th, 2023 AT 2:06 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,756 POSTS
Because the spark is inconsistent it could be the crankshaft angle sensor. Here is the location so you can check it out. Check out the images (below). Please let us know what happens.
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Saturday, May 6th, 2023 AT 11:17 AM
Tiny
LOUD PELLETIER
  • MEMBER
  • 39 POSTS
The only thing I found weird is that he has start last fall and I didn’t touch the CKP. How he could have move and can it be CKP that cancel ground pulse to injector or weak ground pulse and I don’t know the code cause the BCM act really weird recently he don’t recognize the truck 8 month ago the truck start fine run fine And suddenly the BCM decides not to recognize anything and I remove the chip in the radio that makes the pass lock issue.
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Sunday, May 7th, 2023 AT 7:59 AM
Tiny
KEN L
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I have seen a bad BCM cause this problem. Here is the location and how to replace it. You can get a preprogrammed unit by searching Google or Ebay. Check out the images (below). Please let us know what happens.
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Sunday, May 7th, 2023 AT 11:36 AM
Tiny
LOUD PELLETIER
  • MEMBER
  • 39 POSTS
Cause crank no start and all symptom I told you before.
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Monday, May 8th, 2023 AT 8:25 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,756 POSTS
So to recap:

Have 62 psi of fuel
Getting strong spark
good compression
runs on starting fluid
getting injector pulse
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Wednesday, May 10th, 2023 AT 10:37 AM

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