When you rev up the motor (not driving, just rev up to lets say 4000 rpm) should the FP fall or rise on our cars?

Thanks, Jason

 

idling my car is at 38 psi when i rev it up then it goes to 45psi. so to answer your question it goes up.

 

Ok lets say fuel pressure drops, What will this do and why would it drop?
It drops on my camaro from 40 to about 30

I have a Holley Adj. Fuel pressure regulator a NOS inline pump along with the stock in tank, and MSD 50 lbs/hr injectors.

 

My experience with lowered fuel pressure is that the car will not run "up to par" so to speak and when you get up in the rpm's, it is harder to get them up any higher. And 2nd, don't know the setup in your car, but you should have more than 40psi in the 1st place.
Just my .02

 

My car was tuned at 38 ponds static (no vacuum lines hooked up to pressure regulator) When I put the lines on it goes to about 40 # or so maybe 42 I cant remember.
But when I rev the motor the fuel Pressure drops big time. does that mean the pumps are not enough, bad injectors, lines too small?

Also from reading it looks like fuel pressure should drop when you hook up the vacuum lines. Mine goes up? Man I gotta do some more reading on this.

Any help would be appreciated guys!

Thanks

 

TTT

 

Man I am having the same problem here. My car dropped 8 to 10 psi, revving w/o load, with vacumm hose connected. I replaced my filter with a new one, and now it goes down about 4 psi. My performance was restored a little, but not enough. Everyone is telling me it should be around 43 psi at WOT. I am about 8 psi off!!! I will turn up my fuel pressure tommorrow to see what is up. I still have stock fuel pump though.

Is your performance not up to par?

 

Fuel pressure is inversely proportional to manifold vacuum.... the more vacuum the less fuel pressure.

Rev'ing the engine is not a good indicator of fuel pressure. It would go up immediately after snapping the throttle open, go down as the vacuum stablizes, and then go down further when the throttle is closed. It should be ~43.5 psi with the vacuum removed. With a good fuel filter installed you need to place the engine under load, go WOT, and bring the revs up. It should get close to 43.5 psi. It's best to tape the fuel pressure gauge to the windshield and have a buddy watch it while you drive.

 

i dont know if its because i have a 93 (22lb injectors) or what but i get 30psi at idle and 38-40 max at wot .

 

GM states that fuel pressure on these cars should be between 41-47 psi...they don't state whether or not that is under a load, but I would be assuming so.

 

Under load for two reasons.

1.) if there is any vacuum it will lower the fuel pressure. WOT=almost atmospheric/little vacuum
2.) testing with full load may uncover fuel delivery problems that may not arise with low fuel demands (ie, dying fuel pump, clogged filter, etc.)

 

There you have it!!!