INTRO
Hey everyone, I Have a 2005 GMC jimmy that has the fueling issues from hell. It all started last year with a dreaded 'no start' after filling up the truck. Was able to run it on ether/starting fluid but other than that nothing. Naturally I ended up changing the entire fuel pump + sending unit assembly and all was good. Fast forward one year (11 months and 1 week to be exact) and its acting up again. This time is particularly difficult for me to diagnose, so I need help before all my hair falls out and I gain 50 lbs from binge eating Nutella-to-go's

VIDEO LINK:
SYMPTOMS
- randomly dies, doesnt want to start, turns over, doesnt fire
- cycle key many times, fuel pressure gauge at Schrader valve reads 0 PSI, I can hear the relay clicking
- then, after an arbitrary amount of time, fuel pressure has a normal operating condition is 55 PSI
- at total random, the fuel pressure drops, 50, 40, 30, 20 (starts sputtering), hangs around 10, barely idling, then 0, then she dies
- interestingly enough, when it does work, and I shut it off, the fuel pressure actually climbed from 53 to 60 psi when off (after about 4 minutes)


THEORIES
1) fuel pump is at random not running, faulty fuel pump? unlikely after 11 months but it does happen
2) wiring at fuel pump has disconnected, causing random power on / power off situation. Possible - to investigate
3) fuel pump relay faulty, working intermittently. Unsure how to test since symptoms are very erratic
4) fuel pressure regulator faulty, causing low pressure. Am I looking at this right? Is this hypothesis even reasonable? If the FPR is after the Schrader valve, would this even be possible?


CONCLUSION
My last resort is to buy a new FPR and a new fuel pump relay (if they are cheap) before changing out the pump. The clock is ticking, I have a 12 month warranty and its 11 months and one week lol.

Thanks everyone for reading, I hope I didn't babble!

 

CB
Lift up your hood and go to the fuse box under your hood, you read the legend under the lid and it says which one in the fuel pump relay. You have several other relays that have same number; just trade them around and see if this fixes the problem. I thinking it might be your fuel pump. Sometimes a heavy vibration on your fuel tank will get a sticky pump to run. If this is the case replace, it which I would probably do anyway because of the warranty expiring. soon.
L

 

Good idea. Will swap relays.

Any possibility of it being the regulator or does it only control fuel pressure post rail.

Thx

 

What brand of pump?

BTW, nice write up of your question.

 

I Believe the brand is Spectra

 

Check threads here to be sure but I think the collective opinion is that the only reliable replacement pumps as AC Delco. Because you have the warranty you still might want to replace it with another Spectra although if you have to replace it, you might consider going for the AD Delco one.

 

So just to be clear guys, the point of this thread isn’t to debate which fuel pump is better

the point of this thread is to find out what could cause 0psi at the schrader valve?

fuel pump only?
relay is possible.......
what about the FPR? Does that regulate post rail only?

 

I think the point Christine was trying to make is that anything other than AcDelco, or Delphi pumps Will give u problems....seeing how u believe u used Spectra, I would highly suspect it being your problem.......if u think it could be a Fpr problem, try disconnecting fuel line then try priming the pump.....