Fuel Pressure. Where does it go?

[Perry Mitchell]

I have a fuel pressure gauge installed on the fuel log at the schrader valve location. When the key is switched on, the pump (yes, singular) turns on and the gauge reads 43 psi. Without starting the engine, it looses pressure fairly quick. So where does the fuel go? I recently installed new FIC injectors and the new fuel pressure regulator that Jerry sells. I don't think the injectors are leaking into the oil pan nor do I suspect the regulator. Can it be returning to the tank? This motor is installed in my 67 Camaro.

[mlipmd]

One spot that it could be leaking back is right at the fuel pump, either through the pump or at the outlet connection to the hose. I had that problem recently and found the black GM hose clamp loose at the connection to my primary pump. Replacing all those plastic clamps with SS screw hose clamps solved that problem.

[JG95ZR1]

What?s fairly quick? Less then 10sec or Less then a minute ?


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[Young1]

It leaks back thru bad check valve in pump, cracked hoses or fittings, or loose oem clamps. Remember when replacing hoses they must be in tank high pressure submersible hose. Not cheap.

[Paul Workman]

Yep! Check valve(s) in the pumps also could be leaking. To determine whether it was an injector or the pump(s), after removing the pumps, I was able to blow air (with my mouth) against each of the fuel pump outlets. One of the pumps would definitely allow air to pass back against the normal flow, and the other would not. Replacing the pump with the check valve issue solved the pressure leak-down issue! (With the new pump the fuel pressure at the Schrader valve would drop only ONE PSI over and hour or so (held at 44 w/ switch OFF).