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Okay GM Experts, I need some help. Truck has been sluggish for a little bit now. I checked the fuel pressure and it is low. 48psi is about the highest it will go, if I prime the fuel system a few extra times I can get it up to 50psi. GM specs are ignition ON engine OFF pressure should be 58-62psi. Engine running, fuel pressure is about 48psi, If the vacuum line is disconnected I get 58psi. I realize with high manifold vacuum the pressure should be less since the engine is basically sucking on the fuel injector, but this just isn’t right. I’ve followed the factory service manual exactly and I always end up with “replace fuel pressure regulator” The original regulator I pulled out appeared aftermarket so I bought an OEM one. Same thing, so just to be sure I bought a second one – same thing. The fuel pump is new as well. If the return line is restricted pressure will hit 90-100psi. So I got plenty of pressure, but I can’t figure why I can’t get 58-62psi Ignition ON, engine OFF and somewhere close to that engine running. It’s really driving me nuts. I can’t see myself having 3 bad regulators. Oh, fuel filter is new too. The old one was perfectly clean.
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Are you sure you have good vacuum getting to the fuel pressure regulator?
There could be a bad vacuum hose or a hose that’s not sealing good.
The pump sounds like it’s fine and the regulator is new so i would make sure it is getting the proper vacuum to it.With a new fuel pump, I presume the gas tank needed to be dropped? Any chance the fuel line from the pump to the tank got slightly crimped, thus providing a lower overall fuel pressure? It’s a long shot, but just wanted to provide that input.
55-60psi is the spec for this vehicle.
If you leave the fuel pressure regulator unhooked does the truck run ok then?
This still sounds like a problem with the pressure regulator, are you 100% sure it’s installed correctly?Does the truck have the vortech system? If so, did you notice any pooling in the intake when you replaced the regulator? Those poppet injectors are known to fail.
Actually for the fuel pump change I just unbolted the bed and used my engine hoist to lift it up. It was super easy, I’m glad I didn’t drop the tank.
Yes, it is installed correctly. The o-rings get lubed with engine oil and it presses into the rail and then a little clip keeps it secured.
Beefy, I probably should have mentioned I have a 5.3 but that’s my fault. No spider setup here
I actually figured out what the problem was by chance. I noticed the AC Delco regulator has an adjustment screw that is a T10 Torx security. So, I gave it 2 complete turns and that bumped up my pressure to 58psi key ON engine OFF. At idle my fuel pressure is 54psi. I’m pretty happy right now because I was REALLY stumped. There must be a reason why they put an adjustment screw in and I’m glad they did. I feel sorry for the guys who buy the non OEM ones without an adjustment. I really haven’t driven the truck much, but it does seem to start easier and feel stronger than it did previously.
Awesome Third Gear,
Thanks for the fix. It is great to be able to file this away, in case we ever come across a similar concern. Thanks again.
Interesting I’m glad you found that. I was going to go the rout of too much resistance in the fuel pump circuit causing it not to put out like it should but the fact that it went up so much when you ‘dead headed’ the pump would indicate the pump is able to put out plenty of volume. Thanks for posting the fix, if you haven’t already please change the ‘traffic light’ to green.
54 is still 1psi too low, I would bump it up just a little bit more.
But if it runs fine and your happy with it then dont mess with it.
Glad you got it fixed.I think the 54psi at idle is okay because it is 58psi when the pump primes prior to starting. I think you can get a 3-10psi drop in pressure once the regulator gets vacuum. I agree that It definitely wouldn’t hurt to bump it up a little bit since the spec is 58-62psi. Although some places the service manual says 55-62. I like 58-62 better though.
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