Stock Fuel Pressure Regulator

[Zero4488]

I have a couple questions about the the location and function of a stock regulator on a 98-02 F-Body. I already know it's located in the pump assembly, and I check all data and I know it reads off the return line. Now what is it referencing to adjust pressure? At WOT should the fuel pressure at the rail be increasing or decreasing? Could some one post a diagram of how the fuel pressure regulator should be hooked up to the pump assembly with all the lines, crudely drawn illustrations will be fine as long as it gets the idea across. The reason I am asking is because I used to have a fuel pressure gauge on the car and I can remember that at WOT the fuel pressure at the rail would increase, now if I hook up a gauge the fuel pressure drops. I think this might be cause my issue with the car breaking up in high rpm's being I've changed everything else including the fuel pump. I mean primed the fuel pump is in check and even at an idle everything seems fine. The theory seems to be logical. All input on the subject would be great.

-Dave

[S.J.SLEEPER]

change the f'n thing.

[Zero4488]

Originally Posted by S.J.SLEEPER

change the f'n thing.

I'm getting around to it....I just wanna figure out the workings of it....since it's not like a regular MAP reference unit....

[S.J.SLEEPER]

I believe the fpr is preset @ 53psi
and the return line feeds the pressure regulator on the fuel module which diverts fuel back into the bucket/pump module

note: return line located @ T-block in front of fuel filter by rear control arm-frame mounting area

[Zero4488]

Originally Posted by S.J.SLEEPER

I believe the fpr is preset @ 53psi
and the return line feeds the pressure regulator on the fuel module which diverts fuel back into the bucket/pump module

note: return line located @ T-block in front of fuel filter by rear control arm-frame mounting area

Now being that it's preset and fuel pressure is a constant, what makes the pressure go up at WOT? Is it the increased flow past the regulator while the injectors pulsing faster what increases the pressure?

[S.J.SLEEPER]

pressure is not supposed to increase, its supposed to stay within a couple psi, its the pulse width/duty cylce that changes relevant to maf/map/tps/iat voltage signals sent to pcm.

f.p. can range lower or higher than 58psi depending on fuel consumption of engine. (with 2-5psi +/- if it runs in the low 40's (41-43psi) than you either
1)don't have a strong enough pump/proper voltage to pump
2)restricted filter
3)fpr leaking back/holding lower than normal pressure.

fpr's are known to go bad in gms,normally rail type or under intake manifold type like in the vortecs.
whats the milage on your car?

does bill have a adjustble fpr? if so tap in to return line @ T-block set to 53-58psi and than check car for f.p. @ wot.
if drops off than you have a pump/voltage issue
doesn't than you have a bad fpr

[Zero4488]

I'm aware the the pulse width/duty cycle changes and allows more fuel to pass through the injector...I'm just trying to figure out what has changed....I distinctly remember the fuel pressure going up when I went WOT....now it drops...and breaks up....as far a a pump and voltage, Bill and I installed a racetronix pump with the hotwire kit. I'm not worried about either of those. I'm probably just going to check all the lines at the pump assembly and make sure everything seems to be alright when I replace the regulator. As far as mileage my car up there....so I wouldn't be surprised if it's just a stupid part that has gone bad over time. I just hope this is a step in the right direction....

Also with the difference in FP, my tune is most likely off. Being injector flow rate changes with the different pressure.