The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Electrical

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 02-20-2018, 11:48 AM   #1
GM man
Registered User
 
GM man's Avatar
 
Join Date: Aug 2011
Location: Gainesville, Texas
Posts: 126
No voltage from PCM fuel relay trigger

This came out of nowhere. I've had it hooked up for several months now and it's worked really good. Now I'm not getting any voltage from my PCM trigger to my fuel pump relay. If I wire around it, the fuel pump kicks on. I've been all over checking wires, fuses, grounds, etc.. and this is baffling me. In a desperate measure, I tried replacing the crank sensor and still nothing. I've read where guys have encountered this kind of issue theirs wound up being wired wrong or a grounding issue. I haven't changed anything up, so I'm at a loss.
__________________

1972 GMC Jimmy 6.0/4L65
1972 Chevrolet long bed 1/2 ton
GM man is offline   Reply With Quote
Old 02-21-2018, 03:34 PM   #2
VetteVet
Msgt USAF Ret
 
VetteVet's Avatar
 
Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,164
Re: No voltage from PCM fuel relay trigger

This is a little out of my league but I kinda understand it. I checked google and found this site with the same problem you are having so I am pasting the link for you.

http://www.pirate4x4.com/forum/gener...fuel-pump.html
__________________
VetteVet

metallic green 67 stepside
74 corvette convertible
1965 Harley sportster
1995 Harley wide glide

Growing old is hell, but it beats the alternative.
VetteVet is offline   Reply With Quote
Old 02-21-2018, 06:24 PM   #3
87Skier
Registered User
 
87Skier's Avatar
 
Join Date: Mar 2014
Location: Corvallis, OR
Posts: 664
Re: No voltage from PCM fuel relay trigger

I think is issue is one of two places. Either an ECM issue, or a wiring issue.

It sounds like you have the wiring figured out. Should have 12 v fused power to relay, good ground, wire to fuel pump, and the ECM signal.

On the ECM side, there could be something that is preventing it from powering up the fuel pump. Like a fault code. Might want to try checking codes, then resetting the computer by disconnecting the battery.
__________________
1972 GMC Jimmy Custom 4.8L (L20)/6L90E/NP205
1989 Chevy Suburban V2500 350/Turbo 400/4.11 gears
1996 Chevy Suburban K1500 350/4L60E
87Skier is offline   Reply With Quote
Old 02-22-2018, 01:35 PM   #4
GM man
Registered User
 
GM man's Avatar
 
Join Date: Aug 2011
Location: Gainesville, Texas
Posts: 126
Re: No voltage from PCM fuel relay trigger

Well I got it going. Cannot tell you what was wrong as I didn't replace anything. The wires I cut while trying to diagnose the issue, I re-soldered and heat shrinked and all of a sudden it's working again. Makes no sense. I've taken my time and carefully inspected every wire, no cuts or slices in any of them to ground out anywhere...I was fixing to get another PCM or just put the fuel pump on a switch, but now it's fixed. Thanks for the help anyway fellas.
__________________

1972 GMC Jimmy 6.0/4L65
1972 Chevrolet long bed 1/2 ton
GM man is offline   Reply With Quote
Old 02-22-2018, 05:51 PM   #5
Wrenchbender Ret
Registered User
 
Join Date: Oct 2005
Location: Lenexa, Kansas
Posts: 4,572
Re: No voltage from PCM fuel relay trigger

If there is a problem with the ignition the ECM won't kick in the fuel pump.
Wrenchbender Ret is offline   Reply With Quote
Old 02-22-2018, 06:57 PM   #6
GM man
Registered User
 
GM man's Avatar
 
Join Date: Aug 2011
Location: Gainesville, Texas
Posts: 126
Re: No voltage from PCM fuel relay trigger

Quote:
Originally Posted by Wrenchbender Ret View Post
If there is a problem with the ignition the ECM won't kick in the fuel pump.
Yeah, I read somewhere that if the crank sensor goes bad that the PCM won't kick the fuel pump on. I replaced it and nothing changed. I could hear the throttle body do it's deal when the key was on, so I'm assuming my PCM was still getting power.
__________________

1972 GMC Jimmy 6.0/4L65
1972 Chevrolet long bed 1/2 ton
GM man is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:30 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com