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 a little 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 is 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 (Racetronix module). 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. I also have the Racetronix hotwire kit, so the pump is without a doubt getting plenty of juice. I'm stumped.

 

time for aftermarket adjustable fpr

 

Maybe, but there has to be something else going on here because I shouldn't have to buy an aftermarket regulator to get the right pressure. On other LSx cars I've had in the past the fuel pressure was always spot on where it was suppose to be.

 

Also, I don't even see anyone that makes an adjustable regulator for these engines. Everything out there is LT1 stuff. Do you have any links?

 

Okay I think I figured it out. The new AC Delco one has a T10 Torx Security screw in it. I gave it about 2 turns and now I'm up to 58psi when the system primes, and at idle it's about 54 psi. So I'm pretty happy right now AND i don't have to look for another regulator.

 

oh yay that is exactly what i was about to chime in with is i thought the factory ones had a t10 adjustment screw. i had a cadallac kick my butt at work over this same issue!!!

 

I drove the truck today, and it is definitely better than it used to be. The throttle response is much improved and if you put your foot into it, it pulls a lot harder. The fuel trims are looking a lot better now too. They are hanging around +/- 3% to where previously the LTs were +11 to +16 and the STs were almost always +4 to +6.

 

That's weird that it was perfect with the vacuum line off. It should be the same as key on, engine off.

 

Glad ya got it figured out, and thanks for sharing the fix, it might help others.

 

Thank you so much for posting this !