Fuel Pressure drops quickly after pump cuts out

[nitefr8r]

2003 Yukon 5.3 flex fuel started not starting on first attempt. rented pressure gauge from autozone and noticed that fuel press initially goes to 52 psi when key is turned and quickly bleeds down to 0 psi if not started. when engine is running it holds a steady 44 psi. Has to be the fuel pressure regulator, right. That's what I thought so I replaced it . Guess what, still did the same thing, so I thought I'd replace the fuel filter, long overdue anyway. By the way that special tool to remove the fuel line from the filter ain't so special, what a pain in the . As your probably guessing that didn't help either.

Any ideas? Shouldn't fuel press hold steady with the engine not running and not bleed off so quickly. I don't believe it's the fuel pump, cause it seems to be doing its part, and I can't find any fuel leaks around the injectors or the fuel rail. The car runs fine and starts first time if you wait a couple seconds after turning the ignition on to start it, but it annoys the hell out of me.

Any suggestions would be much appreciated..

 

[tahoe7689]

I am having the same trouble with my 03 Tahoe 5.3 flex fuel. I have replaced the fuel pressure regulator twice (thinking the first one could be bad). I had my mechanic friend look at it with a fuel pressure gauge, and the pressure drops quickly right after the key is turned to start, like yours. He seems to think it is the fuel pump (I have a new fuel filter btw). My car has the extended start, so it will crank crank crank crank and then start, sometimes it takes longer than others......The mechanic was telling me that our fuel pumps can limp along and run the car, but be hard to start and not hold pressure...so I plan on replacing my pump, because I dont know really what else to do, and I have 150,000 miles on the original pump haha!! Let me know if you figure anything out and ill let you know how it goes after I replace it

 

[nitefr8r]

Surely we're not the only two people on this forum that have had this problem. Not sure I'm ready to drop the tank just yet, but I have to admit I don't know anything about the fuel pump other than it seems to be working. Maybe there's some kind of fuel return check valve that can go bad and allow the pressure to bleed off. Hate to spend the dough on a new pump only to have the same results.
Please let me know if it fixes your problem and any lessons learned dropping the tank. By the way, mine has almost the same mileage as yours 148k.

 

[MeanGreen03]

It's more than likely the fuel pump. These vehicles are notorious for the fuel pumps going out. I'm one of many who have replaced theirs.

 

[nitefr8r]

Did yours start out not starting on the first attempt, or did it just die on ya? Did you install the new one yourself?

 

[MeanGreen03]

It just died one day and wouldn't start up. I did install the new pump myself. It wasn't too fun of a job either but it wasn't too bad.

 

[teggenberger]

hey nightfr8r - did you replace the pump? did that fix it?
I'm having the same issues with my 5.4ltr. '01' GMC Yukon.

 

[FWFascenelli]

OK figgered it out it a "check valve"! it a one way valve that keeps the pressure from leaking back into the tank.

I have a resto-rod runing a 5.3 LS with the same issue. This is a new build, baught a AN6 check valve from summit racing fixed the issue. you just need to put it between the fuel pump and the fuel rail.

good luck

 

[ks03]

I worked on one that did this before. Ended up finding the line between the pump and the top of the sending unit had a pin hole from rubbing against the springs that hold the lower half down to the bottom