Fuel Pressure. Where does it go? - ZR-1 Net Registry Forums

Perry Mitchell · 04-05-2022

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 · 04-05-2022

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 · 04-05-2022

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

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Young1 · 04-05-2022

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 · 04-07-2022

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).

04-05-2022	#1
Perry Mitchell Join Date: Nov 2018 Location: Washington Posts: 98	Fuel Pressure. Where does it go? 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.

04-05-2022	#2
mlipmd Join Date: Mar 2021 Location: Crawfordville, FL Posts: 220	Re: Fuel Pressure. Where does it go? 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.

04-05-2022	#3
JG95ZR1 Join Date: Aug 2017 Location: Queens, NY Posts: 166	Re: Fuel Pressure. Where does it go? What?s fairly quick? Less then 10sec or Less then a minute ? Sent from my iPhone using ZR-1 Net Registry

04-05-2022	#4
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 897	Re: Fuel Pressure. Where does it go? 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. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

04-07-2022	#5
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	Re: Fuel Pressure. Where does it go? 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).