Fuel pressure issue

[Welderdad]

1998 Chevy k3500 Silverado 7.4L

I'm testing at 45-50 psi after truck is warmed up. When revving it'll hit 50 psi and idle around 45 psi.

From what I understand should be 55 to 65.
Truck feels mostly good. But constantly feels a little sluggish. Idles perfect, starts hot or cold. No misses.

I started with fuel pressure regulator, then fuel injectors, lower intake gasket, distributor oil pressure sensor, then I got distracted and did water pump , radiator, alternator, etc.

Back to fuel.

What's on my mind . I was told there are several fuel pressure regulators that fit but only TWO that allow correct flow. Is this true? I can't verify the part number on the one I installed but can verify it was new.

I need to decide to do a new fuel pump, or tear out the new FPR and deconstruct all the hard work I did to get there.

If anyone has the correct part number for the correct fuel pressure regulator I would probably start there as It's a more cost effective route.

Also the part number to the specific fuel pump with assembly would be awesome. There's so many to choose from I don't want to put the wrong on in.

The goal is to keep the truck as close to stock as possible.

 

[movietvet]

You did all that and no fuel filter? Did you do a back pressure test on the catalytic converters?

More Information for WIX 33481

 

[Welderdad]

Oh , yes I did fuel filter as well forgot to mention . I don't know what a back pressure test on cats is. But I will look now. They are stock cats.

 

[Carlaisle]

There is no fuel pressure spec for running pressure, only key on engine off. This is 56-62 and it should hold. If you can visibly see it bleed down you have a problem that needs addressed. There are many fuel pressure regulators that will fit, but only one that has the correct pressure for the stock L29 engine. The part number you want is FP10021. Don't trust any of the parts store interchange lists. You need that exact part. What injectors did you use?

 

[Schurkey]

FIRST thing to do is to verify that the fuel pressure gauge you're using is accurate.

You'll spend the rest of your life chasing a non-existant problem if the gauge is incorrectly showing lower pressure than what the pump/regulator is actually providing.

Next, I'd connect a scan tool, and look at the short- and long-term fuel trims. If the computer isn't adding fuel, the pressure can't be low enough to matter.

 

[Welderdad]

There is no fuel pressure spec for running pressure, only key on engine off. This is 56-62 and it should hold. If you can visibly see it bleed down you have a problem that needs addressed. There are many fuel pressure regulators that will fit, but only one that has the correct pressure for the stock L29 engine. The part number you want is FP10021. Don't trust any of the parts store interchange lists. You need that exact part. What injectors did you use?

Thank you for the part number. I will rerun test engine off key on and report findings.
I used ford Bosch injectors I referenced this forum to find . I'll find that part number.

 

[Welderdad]

FIRST thing to do is to verify that the fuel pressure gauge you're using is accurate.

You'll spend the rest of your life chasing a non-existant problem if the gauge is incorrectly showing lower pressure than what the pump/regulator is actually providing.

Next, I'd connect a scan tool, and look at the short- and long-term fuel trims. If the computer isn't adding fuel, the pressure can't be low enough to matter.

I don't have a 2nd fpr tester or a scan tool. But I will follow up with this today. I can buy one at harber frieght an test and return or just keep if price is right.

 

[Welderdad]

Thank you for the part number. I will rerun test engine off key on and report findings.
I used ford Bosch injectors I referenced this forum to find . I'll find that part number.

Bosch 0280150943 / Ford FOTE-D5B

Unlock Horsepower by replacing your clogged dirty injectors with our professionally 100% rebuilt Flow matched fuel injectors, your engine will run smooth and balanced for maximum performance

www.injectorplanet.com

That link is the exact one I bought injectors from.

 

[Welderdad]

And some more info. I started the fpr mission after I bought the truck from a mechanic he gave me the fpr and lower intake gasket set. He suggested while I was there to do distributor, oil sensor, upper plenum gaskets. I went ahead and did egr gasket and butterfly valve gasket on the intake.

So I bought fuel pressure gauge tested fuel at 35-40 running and it would not start when hot. I did all the above repairs at once including a fuel filter. And now I have no hot start issue at all and better psi while running. Those repairs fixed a leaking rear lower intake oil leak I didn't know about.

I put it back together and it ran way better.

After that I did water pump because it was leaking at its gasket. When that was fixed on the test run it cracked the radiator. My thinking is the correct pressure from new water pump cracked the stock original radiator.

So $500 all aluminum radiator was installed. Then alternator went. Now ac is gone. And steering box is leaking.

This fuel issue has me stumped since day 1 when I bought the truck a year ago. I gotta solve it before I move forward.