Fuel Pressure Leaking Off

[rjeffery]

Hey everyone, I have been reading a lot of back-posts on this site and have learned a lot about my truck. It seems like this place is a weath of information.

I have a 2002 2wd 1500 4.8L with 95,000mi. I have cat-back exhaust, and the K&N FIPK system, no other mods. It seems like I am having the same problem that a few other people are. Every now and then (usually when the engine is cold), I will turn the key and it will crank and crank but wont turn over. Then if I release the key and turn it over again, it will start. Some times it will start fine, other times it will hesitate and splutter like there is not enough fuel getting to the engine.

This started happening over the summer, and since then, I have replaced the fuel pressure regulator and the fuel filter, both of which helped for a while but the problem still returns.

I have done a fuel pressure test with the following results:
Cold (ignition on, engine off) = 60 psi
Cold start = 52 psi
Engine warm = 51 psi
Engine off = psi leaks off to 0 in under a min

The leak-off leads me to believe that I have a bad fuel pump, or a leaky injector. I am trying to find a fuel-line shut-off valve so that I can isolate the injectors to try and narrow it down.

Any input that you can give me is very much appreciated. Thanks.

[JustSayGo]

You have a huge leak. If it were through an injector you would notice other symptoms. If fuel isn't leaking externally, it is bleeding off through the FPR or the fuel pump check valve. You can remove the return line from the FPR to see if fuel is leaking as the gauge indicates the bleed off. Then you will know that you do need to replace your fuel pump if fuel isn't leaking through the return line.

[rjeffery]

What exactly is the FPR, and where is it located? Thanks

[rsmith8411]

FPR is the fuel pressure regulator. I don't have a Haynes or other manual in front of me, but it is usually easy to find.

[rjeffery]

OK, so I removed the return line from the FPR, covered the line with my finger, and turned the ignition on. Fuel pressure jumped up to 80 psi or so, then bled down to zero again. I then reconnected the return line, and turned the ignition on, the psi went up to 60 psi or so, then bled down to 0 (ignition still on). What do yall think?

[ravinlun]

Just went through this same problem. I jumpered the fuel pump relay so the pump ran constantly. I had 60 psi, but as soon as I stopped the pump the pressure dropped immediately, with it running and holding pressure it tells you regulator working. I then jumpered the pump on again and clamped the pressure line off (left side and back of engine braided flex line), then turn off pump, pressure should hold. This tells you no injectors leaking. The next step says to replace the pump/level assy, the pump is actually working fine it is just some sensor or ck valve that is bad. Well I replaced mine on yesterday and it works great now, plus my fuel level indicator was going bad also, so fixed two items with one part. good luck with yours.

[twistedtech]

I also say the check valve is bad in the pump.

[hoop22]

I'm having this same problem with my 03 silverado. Replaced the Fuel & air filter and went ahead and gambled on the Fuel PSI regulator. Still has the same problem.

My question is when you do the pressure test, where are you tapping into the fuel system at? Keep in mind I'm a bit lost under the hood and it took awhile to find the PSI regulator.

I can see this is heading towards a fuel pump, but would like to have some confidence behind me when I head to a mechanic. At least I will have ruled out anything that they try and tell me is the problem.

Thanks for the help guys!

[rjeffery]

There is a port on the fuel line right above the passenger side fuel rail. It is covered by a black cap, remove that and connect your pressure gauge to it.

Thanks for everyone's input, I will probably replace the pump as soon as I find one at a reasonable price. Anyone know where I can find a cheap OEM pump?

[ravinlun]

I paid 268 and some change for mine at advance. It has one year warranty with it.