Fuel Pump Not priming
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Freshman User
Joined: Dec 2013
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Fuel Pump Not priming
i have an 87 f150 with 302 efi. i rebuilt the engine in my engine class and it ran before. now i put the engine back it in starts with starting fluid. i replaced the fuel pump relay and main relay but the fuel pump relay does not prime the fuel pump when the key is on or trying to start. but i know it has power because when i take the relay cap off and touch the connections together manually i can then hear the fuel pump build up pressure. what could it be? new pump or bad wires/ connections. or does my truck turning over with out the key have anything to do with it.
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
More than likely a bad computer but you need to ground pin #6 on the test connector with the key on and see if they run then.
If they do then short pin #2 to pin #6 and see if they still run all the time with the key on.
You also need to make sure the small black wire with a green stripe on it has a good connection at the NEG post of the battery.
Let us know what you find.
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If they do then short pin #2 to pin #6 and see if they still run all the time with the key on.
You also need to make sure the small black wire with a green stripe on it has a good connection at the NEG post of the battery.
Let us know what you find.
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Freshman User
Joined: Dec 2013
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Alright so I grounded pin 6 and the fuel pump came on. Barley made a humming noise. And then when I shorted #2 and #6 the fuel pump came on a little louder when I turn the key one. So is it a bad computer?
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
What exactly do you mean when you say,
"or does my truck turning over with out the key have anything to do with it"
that's not real clear, statement could mean many things that would widely differ in cause.
If as simple as can start it without putting the key in the ignition for example? then no just needs a new key tumbler installed.
If cranks over moment you connect the battery? yea might have something to do with your issues.
"or does my truck turning over with out the key have anything to do with it"
that's not real clear, statement could mean many things that would widely differ in cause.
If as simple as can start it without putting the key in the ignition for example? then no just needs a new key tumbler installed.
If cranks over moment you connect the battery? yea might have something to do with your issues.
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