No voltage from PCM fuel relay trigger - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GM man · 02-20-2018, 11:48 AM

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.

**VetteVet** · 02-21-2018, 03:34 PM

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

87Skier · 02-21-2018, 06:24 PM

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.

GM man · 02-22-2018, 01:35 PM

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.

**Wrenchbender Ret** · 02-22-2018, 05:51 PM

If there is a problem with the ignition the ECM won't kick in the fuel pump.

GM man · 02-22-2018, 06:57 PM

Quote:

Originally Posted by Wrenchbender Ret

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.

02-20-2018, 11:48 AM	#1
GM man Registered User Join Date: Aug 2011 Location: Gainesville, Texas Posts: 127	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

02-21-2018, 03:34 PM	#2
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,703	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.

02-21-2018, 06:24 PM	#3
87Skier Registered User Join Date: Mar 2014 Location: Corvallis, OR Posts: 711	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

02-22-2018, 01:35 PM	#4
GM man Registered User Join Date: Aug 2011 Location: Gainesville, Texas Posts: 127	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

02-22-2018, 05:51 PM	#5
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,190	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.



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