fuel pump relay question
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Senior User
Joined: Nov 2004
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From: Hephzibah Ga
fuel pump relay question
I am helping a friend with his 86 f150 and our problem is the fuel pump relay contacts are not closing when you switch the key on. Replaced the relay and it did not help. If I bypass the relay the truck cranks and runs fine. So I think I need to know what sends the signal to the relay telling it to close? I'm not sure how that system works. I am also illiterate to all those abbreviations so please be easy on me. thanks
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Joined: Jan 2001
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From: Virginia
The computer grounds one side of the coil, and that triggers the fuel pump. Find the tan/lightgreen wire going to the relay, and ground it for a test. That should trigger the relay when the key is turned on.
Follow the tan/lightgreen wire as far as you can. It should go to a splice, and one should go to the computer, and the other according to my diagram goes to a "In Process Starting Aid". I am not exactly sure what this is, but it may trigger the relay during cranking. After that, the computer looks at the signals from the distributor, and if it sees them, it assumes the engine is running, and grounds the tan/lightgreen to keep the fuel relay activated.
Follow the tan/lightgreen wire as far as you can. It should go to a splice, and one should go to the computer, and the other according to my diagram goes to a "In Process Starting Aid". I am not exactly sure what this is, but it may trigger the relay during cranking. After that, the computer looks at the signals from the distributor, and if it sees them, it assumes the engine is running, and grounds the tan/lightgreen to keep the fuel relay activated.
