fuel pump problem

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Apr 16, 2015 | 06:43 PM

TIRED-ED

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fuel pump problem

This is my first time on . I bought a 1987 f150 5.0 auto that would not start , replaced the computor ,now it will run ,but only from the frame mounted pump . neither tank pump will run , both in tank pumps are new the truck had been sitting a while , I am getting power at the fuel pump relay & at the inertia switch , but no power at in dash tank selector switch .so what am i missing .

Apr 16, 2015 | 09:24 PM

TobaccoBarn460

Tuned

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From: Ky

If it's like an '89, it should have a separate circuit, protected by a 10 amp fuse.

Apr 16, 2015 | 09:58 PM

subford

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From: Easton,Ks

Well there is no fuse and the power from the inertia switch goes to both the dash tank selector switch and the frame mounted pump.

Sounds like maybe someone did some rewiring.

Apr 16, 2015 | 10:00 PM

TobaccoBarn460

Tuned

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From: Ky

Oops, sorry, that would be a diesel.

If you have power out of the inertia switch you should have power to the selector switch.

The power in to the selector switch on the '89 is Red/white striped wire that should be also at the outlet of the inertia switch.

Again that's on an '89.

Apr 17, 2015 | 10:53 AM

carguy94

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From: southern maryland

how did you go about ordering or getting another PCM and were did it come from.

Apr 21, 2015 | 09:58 PM

TIRED-ED

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Thanks for the replys , first the 15 amp fuel pump fuse is good. second i had 2 cut wires just outside the fire wall but that was easly fixed , i haven't found anything that has been done to the wiring third 1st comp. thru napa to match #s on original ,that is what is in there now , 2nd comp. salvage with correct hol. interchange .I have looked at several trucks 89 -90 that don't have the frame pump like the one on the 87.and I have not been able to find a copy of the wiring harness for the 87.
Thanks for any help you can give me , Ed

Apr 22, 2015 | 07:17 AM

subford

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From: Easton,Ks

The 5.0L did use the 15 amp fuel pump selector fuse. The fuel position in the fuse box was for the 7.5L and 7.3L engines that had the motorized fuel selector valve that you do not have. It was also used for some of the 5.8L and 4.9L engines with the solenoid fuel tank selector valve on the frame.

If you have no power to the selector switch on the dash and the frame pump runs then you have an open wire in the dash area.

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Apr 22, 2015 | 05:21 PM

subford

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From: Easton,Ks

I only have the 1986 and 1988 wiring diagrams and I do not know if the 1987 is like one or the other.
I do not understand what you mean by 8 holes. The selector switch should have 6 places that the wires go into.