Fuel Relay question?
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Joined: Aug 2004
Posts: 98
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From: Miami FL
Fuel Relay question?
my car wont start right now... 
when jump the fuel pump from ecm connector inside the car it runs fine.. when i turn the key to the on position the fuel pump doesnt run... should the pump run with the key in the on position.. i have a 85.. i disconnected the fuel line from the fuel rail. any help would be great
when jump the fuel pump from ecm connector inside the car it runs fine.. when i turn the key to the on position the fuel pump doesnt run... should the pump run with the key in the on position.. i have a 85.. i disconnected the fuel line from the fuel rail. any help would be great
Team Owner
Joined: Aug 2000
Posts: 40,156
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From: San Pedro CA
ok, this is how this works:
The fuel pump is wired in parallel with the oil pressure switch. Once the ECU sees 4psi of oil pressure, it will turn on the FP regardless of what the FP relay says. This is a safety net incase the fuel pressure relay dies.
To get 4psi of oil pressure, you need to crank the engine for about 5 seconds. It won't just fire up.
if this does start the car, then you know the problem is with the relay.
The fuel pump is wired in parallel with the oil pressure switch. Once the ECU sees 4psi of oil pressure, it will turn on the FP regardless of what the FP relay says. This is a safety net incase the fuel pressure relay dies.
To get 4psi of oil pressure, you need to crank the engine for about 5 seconds. It won't just fire up.
if this does start the car, then you know the problem is with the relay.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by rsauron
when i turn the key to the on position the fuel pump doesnt run... should the pump run with the key in the on position.. i have a 85.. i disconnected the fuel line from the fuel rail. any help would be great
RACE ON!!!
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Joined: Aug 2004
Posts: 98
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From: Miami FL
well guys I am not exactly sure how I fixed it but its fixed.. I ran a wire from the battery to ecm connecter to turn the fuel pump on. while the pump was on I tried starting the car... and she fired right up.. shut it off.. unpluged the wire that I ran from the battery.. and she fired right back up... maybe just a loose wire in the relay.. and me futsin with it fixed it.. dunno.. Anyway thanks for the help 
