With ignition on, engine off and pump running, I have between 50-54 psi. As soon as I turn the ignition off the pressure bleeds off to just under 9 psi in under 5 minutes. Could this be a bad regulator? Is that built into the pump, or....??
There is the problem! There are 3 common things that can cause excessive leakdown. The check valve in the fuel pump, the fuel pressure regulator and the fuel lines under the plenum, referred to as the "nut kit"
http://shop.advanceautoparts.com/Pro...rtNumber=55163 To determine if the leak is under the plenum or in the tank, the fuel pump needs to be isolated from the system just after it pressureizes the system. To accomplish this, a temporary valve needs to be installed between the pump and the fuel pressure test port. Open the valve, allow the pump to pressureize the system and immediately shut the valve off. If pressure drops, the problem is under the plenum. If the pressure holds, the problem is in the tank.