Is my fuel pressure ok?
This is a discussion on Is my fuel pressure ok? within the General Help forums, part of the LSx Technical Help Section category; Ok, for a long time my car has not been performing like it used to (see the where'd my power ...
06-04-2006, 12:46 PM #1
Is my fuel pressure ok?
Ok, for a long time my car has not been performing like it used to (see the where'd my power go post for details). Basically, it runs smooth, but bogs when I get on the gas -- very poor throttle response. The problem seems to get worse once the engine is warmed up. It is not a blatant issue (others who drive it don't even think anything is wrong), but I have had it a long time and know something is up -- for one, I can't break the tires loose without using the clutch anymore (ie, just getting on the gas while in gear), and that used to happen to me even on accident.
Anyway, after trying a ton of different things to fix it, I finally bought a fuel pressure gauge and checked that out. My pressure reads 50 psi at key on and 58 at idle. At first, I thought I had found my problem, because the Haynes service manual (and the instructions that came with the gauge) said the pressure should drop 3 to 10 psi when you go from key on (engine off) to idle (I know this sounds wierd, but that's what they say -- it has to do with the manifold vacuum actuating the regulator). Also, the service manual says it should be between 55 and 60 psi (for my car) at key on, and mine was not in this range. So the way I see it, I have two problems: pressure too low at key on, and pressure went up instead of dropping when I started the car.
So last week I took it to a dealer to see if they could sort it out. Their "fuel systems expert" says that there is absolutely nothing wrong with my fuel system (I haven't had a chance to go over the details with him). He must be giving it the ok since my pressure is high enough with the engine running (I know that he did also hook up the pump and regulator to a computer to check them electronically). I also talked to someone else who told me that it doesn't matter if the pressure doesn't drop when you start the car, as long as the pressure when running is good enough.
So what does everyone here think? Is my pressure ok since it's high enough at idle, or could the fact that it goes up instead of dropping like the service manual says it should indicate a potential problem with (possibly) the fuel pressure regulator? Should I further explore the pressure by measuring it at higher rpm's than idle to make sure it stays up around 58 psi (I will do this anyway as soon as get a chance)?
Thanks a lot for the help. I do see the logic that it's ok as long as the pressure is good with the engine on, but I just have trouble reconciling that with the fact that the Hayne's manual says something is wrong if it doesn't drop...
06-04-2006, 06:36 PM #2
- Join Date
- Aug 2005
- Thornton, CO
Red Tint Jewelcoat
- 2008 Trailblazer SS
My stock pressure was 60-62 PSI at idle.
WOT I was hurting it pretty good, but I was at the limit of the stock pump. 53 PSI WOT.
If you are over 53-54 PSI WOT or anytime really you are okay.2008 Trailblazer SS
Yank PTB3600, Kooks 1 7/8" LT's, 4" intake, E-fans, Magnaflow, Sonnax kit, tranny cooler, tune.
Lowered, HID's, tinted.
1999 Pontiac Trans Am WS.6 #1747 SOLD
531.1 RWHP 481.3 FT/Pounds all motor.
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