Fuel Pump ?
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Junior User
Joined: Mar 2008
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From: Prestonsburg Ky
Fuel Pump ?
Just picked up a '86 F250 with a 460 five speed. It has been sitting a while and the fuel pumps are jacked up. Should I just bite the bullet and buy all three new ones or put an electric inline one in?
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From: Virginia
Your truck is not original. They did not offer the 5 speed in 86. Did you just buy this truck? Do you know the history of it? The only trucks in these years that had 3 pumps were the 5.0 efi trucks. The 460's only came with a 4 speed manual, and only had one electric pump in each tank, or a mechanical pump on the engine with a return line.
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Junior User
Joined: Mar 2008
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From: Prestonsburg Ky
Your truck is not original. They did not offer the 5 speed in 86. Did you just buy this truck? Do you know the history of it? The only trucks in these years that had 3 pumps were the 5.0 efi trucks. The 460's only came with a 4 speed manual, and only had one electric pump in each tank, or a mechanical pump on the engine with a return line.
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Joined: Jan 2001
Posts: 56,965
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From: Virginia
The pump thing is still true. Are you sure you are not thinking the switching valve is a pump?
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Junior User
Joined: Mar 2008
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From: Prestonsburg Ky
Maybe. A guy gave me a couple pumps earlier, can I just change one? I couldn't get both to run. And they look a lot different in size, can you tell me which one goes where.
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Laughing Gas
Joined: Apr 2013
Posts: 1,047
Likes: 63
Before you start replacing things have you figured out why the existing pumps don't run? Are they getting any power?
Maybe you've done a bunch of tests already...but if you haven't you might start by supplying power to the fuel pump bypass wire to see if you can get a pump running that way.
The fuel pump bypass wire is wired directly to your fuel pump. It is (should be) attached to one of the small terminals of your starter solenoid. I believe it's attached to the I terminal and the S terminal is your starter signal wire that activates your starter when you hit the key.
Anyway, (MAKE SURE THE TRUCK IS NOT IN GEAR!!! If you jump the wrong wire you could activate the starter and the truck could jump! Not good if you're standing it front of it!!!) you can jump a wire from the positive battery terminal to your fuel pump bypass and listen to see if a pump runs. Just don't leave it hooked up that way very long or you could fry some wiring.
If you do get a pump running via the bypass your problem may be in the main fuel pump power supply circuit.
Maybe you've done a bunch of tests already...but if you haven't you might start by supplying power to the fuel pump bypass wire to see if you can get a pump running that way.
The fuel pump bypass wire is wired directly to your fuel pump. It is (should be) attached to one of the small terminals of your starter solenoid. I believe it's attached to the I terminal and the S terminal is your starter signal wire that activates your starter when you hit the key.
Anyway, (MAKE SURE THE TRUCK IS NOT IN GEAR!!! If you jump the wrong wire you could activate the starter and the truck could jump! Not good if you're standing it front of it!!!) you can jump a wire from the positive battery terminal to your fuel pump bypass and listen to see if a pump runs. Just don't leave it hooked up that way very long or you could fry some wiring.
If you do get a pump running via the bypass your problem may be in the main fuel pump power supply circuit.
Thread Starter
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Junior User
Joined: Mar 2008
Posts: 92
Likes: 0
From: Prestonsburg Ky
Before you start replacing things have you figured out why the existing pumps don't run? Are they getting any power?
Maybe you've done a bunch of tests already...but if you haven't you might start by supplying power to the fuel pump bypass wire to see if you can get a pump running that way.
The fuel pump bypass wire is wired directly to your fuel pump. It is (should be) attached to one of the small terminals of your starter solenoid. I believe it's attached to the I terminal and the S terminal is your starter signal wire that activates your starter when you hit the key.
Anyway, (MAKE SURE THE TRUCK IS NOT IN GEAR!!! If you jump the wrong wire you could activate the starter and the truck could jump! Not good if you're standing it front of it!!!) you can jump a wire from the positive battery terminal to your fuel pump bypass and listen to see if a pump runs. Just don't leave it hooked up that way very long or you could fry some wiring.
If you do get a pump running via the bypass your problem may be in the main fuel pump power supply circuit.
Maybe you've done a bunch of tests already...but if you haven't you might start by supplying power to the fuel pump bypass wire to see if you can get a pump running that way.
The fuel pump bypass wire is wired directly to your fuel pump. It is (should be) attached to one of the small terminals of your starter solenoid. I believe it's attached to the I terminal and the S terminal is your starter signal wire that activates your starter when you hit the key.
Anyway, (MAKE SURE THE TRUCK IS NOT IN GEAR!!! If you jump the wrong wire you could activate the starter and the truck could jump! Not good if you're standing it front of it!!!) you can jump a wire from the positive battery terminal to your fuel pump bypass and listen to see if a pump runs. Just don't leave it hooked up that way very long or you could fry some wiring.
If you do get a pump running via the bypass your problem may be in the main fuel pump power supply circuit.
Will this eliminate the fuel pump relay?
Laughing Gas
Joined: Apr 2013
Posts: 1,047
Likes: 63
It will bypass the inertia switch, fuel pump relay, and oil pressure switch circuit, but not the tank selector relay...
Here's a look at it. No point in replacing in tank pumps before sorting out the power supply.
Here's a look at it. No point in replacing in tank pumps before sorting out the power supply.
Laughing Gas
Joined: Apr 2013
Posts: 1,047
Likes: 63
I've not pulled a fuel tank pump or sender so I don't have any 1st hand experience. however:
Looking at the diagram, if you have in tank pumps you should have at least three wires; power, ground and gauge, and then some fuel hoses, perhaps a supply line, vent line, and a return? Hopefully someone who's been there and done that will chime in.
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