When the car is running, fuel pressure is at 36psi. Doesnt matter if you have the fpr vacuum line on or off. With the car off and you turn the key on the pump kicks on for a couple seconds and gauge reads 36psi while pumping then pump kicks off and fuel pressure instantly drops to 20psi. It loses 2psi every 10 or so minutes. What is going on!

 

Car off, or WOT fuel pressure should be at it's highest setting (about 42.)
Car on and idling fuel pressure should be at it's lowest setting.
As long as the proper pressure is applied from idle to WOT, how quickly it drops when off will only affect crank time.

You may have a faulty fuel pump check valve and, or leaking injectors, if there's no other leak(s) in the system.

 

Would the check valve only alow 36psi when pump runs then 20psi when not pump is not running?

 

I don't know about your last question, but I just tested my fuel pressure 3 days ago. With the key in the on position, pressure was at 40 or so. With motor turned on it was around 42-44 or so. When revving it would stay the same. As I turned it off, it dropped to about 38psi. 1.5 hours later, pressure was around 32-34psi. 2.5 hours after that, psi was around 17-18psi.


If that is completely useless to you, I'm sorry. It's been a long week.

 

I think the check valve in the pump is bad or something. I put a fuel pump in it and it ran good while I drove it home then when I started it to take it around the block then this problem started. That was a month or so ago. I think I might have to drop the dang tank again. I really hope not.

 

Yes, but 36psi is a bit low with the the key on, try cycling the key off/on until you don't hear the fuel pump turn on then, check the pressure.

With the return line briefly restricted (pinched at rubber hose section from engine to frame) the pressure can be from 40.5 to 47psi/key on, and 30.5 to 44psi/idle for 1 hour after restriction is removed.

With the return line restricted turn the key on once the pressure peaks it should hold, if it drops you have a leak, either a weak check valve, or leaking injectors, or a leaky FPR diaphram.

Pressure is inversely proportional to vacuum applied. Less vacuum more pressure, more vacuum less pressure, if the pressure doen't change with vacuum (revving the engine) then it's blocked, or the FPR vacuum chamber is not sealed properly.

 

I think it has something to do with the pump because I took the FPR apart and it was sealed good and when the return line is clamped the pressure should go up to 80psi but it doesnt change anything. I might end up taking it to a speed shop and seeing if they can fix it. I put a pump in it before and I wont do it again.

 

I bought a Holley pump and I'm going to install it 5-7-06. Hopefully this fixes it so I can move on to more important things, like getting a NA TPI into the 11's.