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Replaced front fuel pump; still not working

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Old 09-04-2015, 08:34 PM   #1
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Default Replaced front fuel pump; still not working

Hey guys, first time poster here. Right away I want to say that I'm scouring all the pages of the forum for threads similar to mine in order to find a solution, so I'm not just counting on this one.

Ok I have a 1996 F-150 XLT 4x4 supercab that I've had for nearly a year. The rear pump is the only one that worked for as long as I've had it. Recently I replaced it, and I decided to do the front pump as well. So I cleaned out the front tank and replaced the pump, but the truck is still not getting fuel.

Every time I switch from rear to front, with the truck running, the engine dies after about 10 seconds. It won't start when I have the front tank engaged; or sometimes it will start but run for 3 seconds then die. The rear pump works fine.

I'm at my wit's end here. The only things I can think of are some electrical problem, or a problem with the fuel lines themselves (the ones going to the front tank are heavily corroded; the rear tank lines were replaced last year. I'm sure the new pump is functional, but I've yet to take a multimeter to it.

Suggestions?
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Old 09-18-2015, 02:29 PM   #2
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There is a black box on the frame between the two tanks (kind of there) that is the switching valve. It has all the fuel lines running into it and then to the front. These are sometimes very finicky. It might be that. It was on my 1990. Mine would run on the front tank but not the back, Mine was that valve. Hope this gives you an idea.
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Old 09-18-2015, 05:54 PM   #3
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1996 is a different fuel system from 1990 - no switching valve.
Basically both your tanks are hooked together in one big loop. Whichever tank is pumping, the other one acts as a check valve.
When the pump is pumping the pressure opens a 2nd valve in that same tank to allow fuel to return to that tank when the fuel pressure regulator is open.

To track down your problem - first you can never assume that a new part works the way it should. That would be nice but it very often isn't the case which leads to a lot of frustration.
So is the front pump pumping ? If it is, it's probably either a weak pump or an issue with the lines as you suggested. Those are stainless lines though so that wouldn't be my first guess.
If it is pumping and won't run off that tank, you're going to need a fuel pressure gauge to check pressure at the fuel rail. I've personally seen a 2 week old pump that was only producing 20 psi. Sounded healthy, but not enough pressure to ru

n the truck
If it's not pumping I'd be looking at a faulty pump, short in the wiring or - the usual suspect- a faulty dash switch

1995 F150 fuel lines

Here's a picture of the fuel line system out of the truck. There are 2 halves - from the fuel rail on the motor to the filter = both lines disconnect there= and from the filter back to the tank or tanks. If you do have an issue with the lines to the front tank, you can leave the front part attached to the truck and just remove the section from the filter back. Much simpler to work on that way. Hope that helps.
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Old 09-18-2015, 09:14 PM   #4
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replace the tank selector switch first,, that don't work make sure the plug and pig tails or wires are not damaged I suggest some el contact paste,, if it still giving you grief pull the pump back out make sure the wires leading to the actual pump on the sending unit are undamaged if that don't work .. kill it with fire lol had the same issue on my 92 back worked but front didn't ended up being just a bad connection wire wise at the sending unit
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Old 10-11-2015, 12:40 AM   #5
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A cheap multi-meter could save you from extra work. It would help you see if the front pump is getting power. Without one, you should still be able to hear the pump run when selected. Have someone turn the key to on, while the rear is engaged and listen to the sound as it switches on. Releasing some of the pressure from the line will allow it to pump for a second or two. Then switch to the front and have the key put to on again. If its not running, again it would be helpful to know if its getting power. I too have had a faulty new pump and that was right from FORD.

The switch is a good guess also but its just best to have that multi-meter. You should be able to get an inexpensive one for under $10. I use a $3 meter I bought from harbor freight for simple stuff like this as my better meter sits in my tool box for more involved stuff.
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Old 10-22-2015, 07:02 PM   #6
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Just updating. My pump has been loud as hell for close to a year now. I bought a vacuum testing gauge and tested the pump. It still makes 26 in/Hg so the noise does not mean it's bad it's just noisy as the one bearing goes bad but still completely functional.
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Old 10-23-2015, 11:01 PM   #7
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Just a quick check pull ecu and smell it or open it if it smells like dead fish or see corroded caps replace it and take it to part store with u so they can match the numbers on ecu
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