ChevyTuffD.A.

I have been having some trouble with my car cutting out and being down on power. I took some fuel pressure readings today from the schrader valve and this is what I got.

At idle with car running pressure holds steady at about 38psi the only thing out of the normal is that when the engine is revved up to about 5k in park the pressure goes up to about 42psi and when the gas is let off it drops to about 32 psi and then rebounds back up to idle pressure which is about 38psi. Is the pressure supposed to drop that low when the gas is let off? Would this be a problem with the fuel pump or the FPR? That is if the pressure is supposed to drop that far when the gas is let off. We tested the pressure right after this on my friends 93 z28 and his dropped to about 38-40 when he let off the gas. Any info is appreciated. Thanks, Dustin.

shoebox

Sounds perfectly normal to me. Fuel pressure will act inversely with vacuum.

1racerdude

Tape the guage to the windshield and watch it and run the snot out of it. That will tell ya if it is low or not.

OBE1 95Z28

Reving the engine in neutral doesn't put a big demand on the fuel system. As stated above, tape the gauge to your windshield and test it under driving conditions (load). Your fuel pressure regulator has a vacuum line; this is what causes your fuel pressure to rise when you accelerate (less vacuum) and drop when you decelerate (more vacuum).