Computer or wiring? 93 Fuel issues.
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Joined: Sep 2010
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From: Kentucky
Computer or wiring? 93 Fuel issues.
Hello fellow Ford owners. I bought a 93 Bronco a couple weeks ago( I know its not a truck but I have 3 F150s) it has 93,000 miles and is in perfect shape. It is a 5.0 AT and is all original one owner Bronco. It set for about 4 years in a garage before I bought it and it ran great. About 2 nights ago I drove about 20 miles and stopped for gas. I restart the truck and drive about 10 feet and it quits like I turn off the key.
I checked fuses and relays and found the fuel pump fuse for the FP relay blown and changed it and it popped as soon as I turn on the key. Thinking I had a bad fuel pump I changed it and had no power to the pump. I pulled the FP relay and I have power on 3 sides of the relay. I have 12v on the yellow,red,and lt blue/orange. I thought I should have a ground in there somewhere. If I cut the lt.blue/orange wire and ground it going to the relay the pump runs fine. Does the computer ground this wire? Does it sound like I have a bad computer or something else going on?
I checked fuses and relays and found the fuel pump fuse for the FP relay blown and changed it and it popped as soon as I turn on the key. Thinking I had a bad fuel pump I changed it and had no power to the pump. I pulled the FP relay and I have power on 3 sides of the relay. I have 12v on the yellow,red,and lt blue/orange. I thought I should have a ground in there somewhere. If I cut the lt.blue/orange wire and ground it going to the relay the pump runs fine. Does the computer ground this wire? Does it sound like I have a bad computer or something else going on?
Fleet Owner
Joined: Aug 2005
Posts: 23,667
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From: Easton,Ks
Yes the computer grounds the blue/orange wire to turn on the fuel pump.
The red wire is the power to the coil of the fuel pump relay and it comes from the PCM Power relay.
The yellow wire comes from the starter relay battery side to power the common contact of the fuel pump relay.
The dark green wire with a yellow stripe comes from the NO contact of the fuel pump relay and goes to the fuel pump.
It is normal to have power on the three wires with the key on and the engine not running.
I would look somewhere else beside the computer for your short.
I will post you a diagram on my next post in a few minutes and by the way a Bronco is classed as a truck.
The red wire is the power to the coil of the fuel pump relay and it comes from the PCM Power relay.
The yellow wire comes from the starter relay battery side to power the common contact of the fuel pump relay.
The dark green wire with a yellow stripe comes from the NO contact of the fuel pump relay and goes to the fuel pump.
It is normal to have power on the three wires with the key on and the engine not running.
I would look somewhere else beside the computer for your short.
I will post you a diagram on my next post in a few minutes and by the way a Bronco is classed as a truck.
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
I have 12v on the yellow,red,and lt blue/orange. I thought I should have a ground in there somewhere. If I cut the lt.blue/orange wire and ground it going to the relay the pump runs fine. Does the computer ground this wire? Does it sound like I have a bad computer or something else going on?
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From: Kentucky
Ok I traced out the wires from the computer to relay,STI connector,inertia switch and pcm/eec relay. I also traced the harness to the fuel pump and checked the grounds for the computer and case ground. Everything has checked out so far. The only thing even slightly wrong with the truck was the outer ring on the key switch would spin completely around sometimes w/o the key in. I have a 96 F150 5speed 4x4 OBD2 small lift with a mild 351w,fresh rebuilt in the fall. Was planning on swapping the complete drivetrain over in the spring. With this donor truck how hard would this OBD2 swap be? How much of the computer harness is under the dash itself? Sorry I knew it was classified as a truck w/ the body on frame and all its just that I was in the F150 section as yall have taught me a lot though the years. Thanks for any insight on this.
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