Fuel pump or relay??
Thread Starter
Racer
Joined: Oct 2001
Posts: 262
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From: Palos Hills IL
Fuel pump or relay??
Can I determine if the pump is going or the relay is bad. I got a code 54 once. I hooked up the fuel pressure gauge and with the pressure set at 43 psi, with vaccum line off. Vaccum line hooked back up under moderate acceleration the gauge is reading about 37 psi. Car feels like it's running out of gas, especially under acceleration. I guess I know what I have to do, I'm just looking for a little verification. Any way that the relay would cause what seems like a bad pump? 
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
If the car feels like it's running out of gas, the pump may be weak. The relay is only one of the sources of power to the pump. If the pump is running, it's getting power. If the pump runs for the first 2 seconds after the key is turned to "ON", the relay is working. Hook up a pressure gauge and go for a ride. Operate the engine where it will have the greatest fuel demand, and watch for falling fuel pressure. If the pressure drops, check and/or change the fuel filter and sock. Look for kinks or other problems with the fuel lines. If no other problems are found, it's probably time for a new pump. If the pressure doesn't drop on the test drive, look elsewhere.
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RACE ON!!!
Thread Starter
Racer
Joined: Oct 2001
Posts: 262
Likes: 0
From: Palos Hills IL
OK. I changed the filter today and took it for a ride. It really didn't make much difference. I still have the guage taped to the windshield. I have the pressure set at 42 with the vacuum off, then hook up the vacuum and take it for a ride. Under slight accelleration the vacuum drops to about 36, under hard accelleration it will pick up to about 40, and I still have a miss while accellerating. So if I understood CFI-EFI correct, the reley either works or not, so if seems like the pump is at least, weak. I did just get the motor back together. I added a bigger cam, better springs, vavle job and shaved the heads for a little more compression. Ski is doing the tune for me. The tune is really close, but before I go any further with that I need to figure out it this pump is bad or not.
Instructor
Joined: Jan 2004
Posts: 178
Likes: 3
From: Evansville IN
The fuel relay's sole purpose is to pressurize system at start up. Relay only powers pump for a few seconds at first turn of key. The oil pressure switch takes over after car is running. Maybe you have a oil pressure switch on its way out.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by richdwyer
The fuel relay's sole purpose is to pressurize system at start up. Relay only powers pump for a few seconds at first turn of key. The oil pressure switch takes over after car is running. Maybe you have a oil pressure switch on its way out.
Originally Posted by Kwik88
So if I understood CFI-EFI correct, the reley either works or not
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