Fuel problem
Thread Starter
Cruising
Joined: Jun 2018
Posts: 11
Likes: 2
From: Victoria BC
Fuel problem
I have a 1988 vette with fuel problems. I have recently purchased and only have verbal diagnosis from previous owner. The original problem was fuel in the oil. The fuel pressure regulator was replaced, the injectors were replaced. I have checked the return line and it's clear, I put a pressure gauge on the schrader valve, when I turn on the ignition the fuel pump starts up and the gauge moves up to 45 lbs and I hear I click noise on the motor and the pressure drops to zero on the gauge. That may be the check valve on the fuel feed line but probably not the reason for fuel in the oil. Any ideas?
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
The fuel relay comes on for about 2 or 3 seconds when you turn the key on. So, yes it's likely the check valve causing the fuel pressure to drop.
You can check the regulator by pinching off the return line. You should see a higher pressure and it wouldn't drop if the regulator is leaking. But, considering the regulator holds 45psi correctly it's likely OK.
I have run an EFI engine for years without a check valve. It can take a little longer to start after sitting all winter. Otherwise, it starts just fine. Generally speaking, GM puts both ends of the fuel line loop at the bottom of the tank under the fuel level. So, there is no path for air to get into the lines meaning it should pressurize quickly once the pump starts to run. You seeing 45psi quickly is confirming this.
The only places fuel could get in the oil is the injectors or regulator. So, besides the pressure dropping quickly, what other issues do you still have?
You can check the regulator by pinching off the return line. You should see a higher pressure and it wouldn't drop if the regulator is leaking. But, considering the regulator holds 45psi correctly it's likely OK.
I have run an EFI engine for years without a check valve. It can take a little longer to start after sitting all winter. Otherwise, it starts just fine. Generally speaking, GM puts both ends of the fuel line loop at the bottom of the tank under the fuel level. So, there is no path for air to get into the lines meaning it should pressurize quickly once the pump starts to run. You seeing 45psi quickly is confirming this.
The only places fuel could get in the oil is the injectors or regulator. So, besides the pressure dropping quickly, what other issues do you still have?
Thread Starter
Cruising
Joined: Jun 2018
Posts: 11
Likes: 2
From: Victoria BC
So if I turn the key on, and the fuel pump engages, and the pressure quickly comes up to 45 psi, then I hear a click under the hood ( presumably the FPR) and the pressure then immediately drops to 0. Shouldn't the fuel pump kick back on to try and maintain pressure? As it is now I have to turn off the ignition and turn it on again to get the pump to kick on, then the click again, and sudden drop in pressure.
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
No, after the 2 second pump prime the pump won't come on again until you start cranking the engine. Starting with 0 pressure will make the cranking time slightly longer, but it won't stop it from starting and running.
