Fuel System Problems
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Fuel System Problems
I have a 1984 F250 4x4 with a 460, and It died on me the other day after running for a day or two after I reset the fuel pump shut off switch.
There was no gas getting to the carb, and I couldnt hear the fuel pump so I figured that switch went on again, but i checked it and its good.
So I dropped the gas tank thinking Its the pump, But the pump runs when I attach some wires to the terminals on the tank. But I tested the harness that fits onto the terminals and I found that there are three wires going to the pump, A red, a black (the ground), and a blue (the fuel gauge).
When the ignition is on, There is fire to the blue wire but not the red, which Im assuming powers the pump since the pump wont run with the harness attached.
So, the only other problem I can think of is the relay...which I also replaced!! Am I missing something else that could be the problem?
There was no gas getting to the carb, and I couldnt hear the fuel pump so I figured that switch went on again, but i checked it and its good.
So I dropped the gas tank thinking Its the pump, But the pump runs when I attach some wires to the terminals on the tank. But I tested the harness that fits onto the terminals and I found that there are three wires going to the pump, A red, a black (the ground), and a blue (the fuel gauge).
When the ignition is on, There is fire to the blue wire but not the red, which Im assuming powers the pump since the pump wont run with the harness attached.
So, the only other problem I can think of is the relay...which I also replaced!! Am I missing something else that could be the problem?
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Joined: Jan 2001
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From: Virginia
You should have power when cranking. The starter solenoid is feeding the selector switch in the dash(if you have or had dual tanks) which feeds red wire directly during starting. After the engine fires, the relay feeds the selector switch, which feeds the red wire. The relay is activated by a oil pressure switch in the engine.
People have lots of problems with this system. If you do a search, you will find lots of info. Search like this; +460 +fuel
People have lots of problems with this system. If you do a search, you will find lots of info. Search like this; +460 +fuel
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Ok, well I searched all over and definitely learned alot. When I went to poking around, I found several wires spliced into, or missing! I spent all day today pulling out old ones and replacing some leading into the relays. (
I guess the previous owner liked wiring things together or something, since this is a recent purchase of mine) Anyway, now, when I crank, the pump does run, however it does not run when I turn the key halfway. Shouldn't the pump run for a few seconds to prime the lines if you turn the key? I know most other trucks do, I can hear them all the time... Did I miss a wire? Is there another relay? Is it the ignition switch?
I guess the previous owner liked wiring things together or something, since this is a recent purchase of mine) Anyway, now, when I crank, the pump does run, however it does not run when I turn the key halfway. Shouldn't the pump run for a few seconds to prime the lines if you turn the key? I know most other trucks do, I can hear them all the time... Did I miss a wire? Is there another relay? Is it the ignition switch?
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From: Virginia
The pump only runs when the starter solenoid is activated. After that, the engine has to build oil pressure for the pump to keep running.
You where asking in the Elec forum about a diagram, and the Haynes has this circuit in it. It's called "hot fuel handling". Most people get frustrated and just wire the pumps to a manual switch, or a relay off the keyswitch.
You where asking in the Elec forum about a diagram, and the Haynes has this circuit in it. It's called "hot fuel handling". Most people get frustrated and just wire the pumps to a manual switch, or a relay off the keyswitch.
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Well I am definitely frustrated and im very close to rigging something up!!! Ok, another question, the pump should run when the solenoid is activated which is when the key is on, right? sooo, the terminal labeled "I" on the solenoid should be hot, right? Mine, isnt so does that mean its the ignition switch or starting solenoid? But I also ran a wire from the positive terminal on the battery to that "I" terminal and still nothing turned on... I am very confused
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Ok, I tried a bunch of things again this evening and found that If I put a wire from the battery cable to the terminal "I" on the starting solenoid, AND have the ignition on, the pump runs! So what exactly does this mean? Is the ignition switch out? Still confused, what do ya'll think?
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Joined: Jun 2004
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From: Niceville, FL.
Pump should run in "Start" with full voltage and in "Run" with reduced voltage after engine starts and builds sufficient fuel pressure. If you're not getting voltage on the small terminal (I?) the contacts may be bad. You can move the pump wire over to the large starter terminal. Pump wire should be a blue fusible link to a diode to a Pink/Black Hash wire.
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