Fuel pressure issue

devilblue14 · September 5, 2014

I am having a fuel pressure issue with my 99 z71 with the 5.3. when i initially prime the fuel rail the pressure comes up to the desired 58-60 psi. The problem i am having is that immediately after the fuel pump is done priming the fuel rail the pressure drops off to zero in less than 3 seconds. I have replaced the fuel pump already and it is still doing the same thing. I checked the fuel pressure regulator and it is ok. Im kind of stuck and looking for suggestions.

00Silverado4x4 · September 5, 2014

As far as I know the regulator is where the check valve is located that keeps the fuel pressure up when not running. I think you may want to take a closer look at that. If not, then you must have a fuel leak somewhere.

bossier62guy · September 5, 2014

Does the truck start? If so what's the pressure when the engine is running? Was this the same problem w/ the previous fuel pump? What brand of fuel pump did you install? The check valve that holds the pressure is part of the fuel pump assembly....not the regulator. I suppose you could have an injector stuck open, etc. but that's bleeding off really quick.

devilblue14 · September 6, 2014

Does the truck start? If so what's the pressure when the engine is running? Was this the same problem w/ the previous fuel pump? What brand of fuel pump did you install? The check valve that holds the pressure is part of the fuel pump assembly....not the regulator. I suppose you could have an injector stuck open, etc. but that's bleeding off really quick.

Yeah the truck starts, but sometimes it takes a couple tries before she actually runs. the fuel pressure is 51 when running. This is exactly what the old fuel pump was doing. I bought a delphi fuel pump off of rock auto and installed it.

bossier62guy · September 6, 2014

Did you take the vacuum line off of the regulator as was suggested earlier to make sure you aren't losing pressure there? If it's dry my guess is you have a leaking injector(s) but you'll need special tools to verify that. BTW, you did put in a new fuel filter when the pump was changed right?

dukbludvl · January 22, 2015

I'm having the same issue on my 5.3L 2000 yukon with 330k miles on it; it used to fire right up, but now it sometimes takes a few seconds to turn over, mostly on the first start of the day when I leave the house in the morning; I tested the fuel pressure today and this is what I got (using what I assume is a cheap loaner tool from AutoZone):

* cycled key to IGN (but did not start) 3 times so it would build up pressure; the first time I turned to IGN it only went to 15 or 20 psi, but it built up to 55psi after 3 or so cycles to IGN; pressure reads 55 while pump is priming for the first few seconds, then when pump stops priming (which I can hear the whine of it clearly), the pressure drops to about 53 and holds steady; then, when I start the engine the pressure drops to about 50 and holds steady; with the engine running, I pulled the vacuum hose off the fuel pressure regulator and the PSI jumped up to about 58, which I think is what it's supposed to do, right? I replaced the vaccuum hose and it goes back down to 50-53 psi with the engine running; when I turn the engine off, it drops to about 48-50 and seems to stay there at least for a while; after a few hours, it had dropped to 40 psi;
can anyone who knows what they're doing when it comes to this stuff tell me first of all if i have any issues based on these readings, and if so, what you think it might be?

I replaced the original fuel pump in June 2010 when I was at 202k miles, so that was about 130k miles ago;

Please help, thanks!

00Silverado4x4 · January 22, 2015

From what I've read up on here, it sounds like your fuel pressure regulator is going bad on you. There is a way to confirm that, I just can't remember how right off hand.

dukbludvl · January 24, 2015

Can anyone confirm this - that it's likely that my fuel pressure regulator is bad, and of there's a way to know for sure

8.1HD/ALLISON · January 24, 2015

If I recall you should be seeing 62 psi minimum. Sounds like a weak pump. If the fuel pressure went up when removing vacuum hose from regulator, and its not leaking, regulator is good.

dukbludvl · February 15, 2015

Is it possible that my fuel pressure regulator is bad even though i'm not seeing any gas when i pull the vacuum line there? My 2000 yukon with 330k miles recently started having a long crank issue. It sometimes takes 1-2 seconds, sometimes longer before it starts. Previously, it has always started really quickly (much faster compared to my wife's 2007 accord, which I always think cranks a long time when I start it by comparison to my yukon). I recently changed plugs, wires, engine air filter, fuel filter and cleaned throttle body and MAF sensor. None of that has helped. I'm on the second fuel pump (it now has about 120k miles on it in about 4 years), so maybe it's the pump going again? But, I'm wondering if it might be the fuel pressure regulator, even though I'm not seeing gas in the line. I'd rather replace the FPR for $80 than the fuel pump for $600. What do you guys think - could it be the FPR? It idles, accelerates and runs like normal once started.

Steve M Jones · February 12, 2020

I have 2011, 1500 Silverado with a 6.2l motor and it’s dropping dropping pressure when you go to accelerate. I replaced the fuel pump about 30k miles ago with a Delphi unit and have had no problems until now so I replaced the fuel module above the tank and the codes went away now it’s still cutting out with no codes coming up. It’s holding at 58 psi but then at an idle it cut out to about 20 psi. The cranking psi is 78, any ideas? What is the running pressure for a 6.2l suppose to be?