My fuel pump has gone out in both tanks on my '90 F-150 1/2 ton...does anyone know how hard it is to drop the tank and replace the front tanks pump? im going to do this Sunday, so any help before then would help me out..... thx

 

thats preetty rare, have you checked to make sure its not a bad switch, fuze, unplugged controler ,etc...?bob. its not that hard if the tank is empty , when you get it down , lengthen the hoses to make it esier to replace

 

Not sure where the switch, fuse or controler is...its got a half tank full...might siphen it out.....the pump wont prime most of the time...if you could tell me where the switch or fuse would be that would help me out alot....the repair manual doesnt help me worth a flip......

 

Well, the computer turns the pump on and off, via the fuel pump relay. The fp relay is the green one that is attached to the rear of the air filter housing. The it is just a matter of chasing wires to find out where the problem is. From the fp relay, the wire goes into the cab, to the inertia switch (at least on my '87, the '90 might be slightly different), then to the fuel pump switch in the dash, then it splits from there to the two tanks. If you have a high pressure in-line pump on the frame (don't think they did in '90) it would split off from the output of the inertia switch.

 

thx...well ive got the fp relay in my hand...about to go get a new one..ill let u know if that was it..if not..ill be back

 

I have another question concerning my fuel pump....im not much of an electrician but with the key in the on position i tested the wires 2 were hot...with if off only one was hot...i do believe that one stays hot all the time...with this in mind does this mean that my fuel pump is good? also my inertia switch "button" was pushed down, meaning it was ok......the only other thing i can think of is the fuel pump is bad....anybody have any other 2 cents they wanna add??

 

You've got 4 wires on the relay: one has constant 12V (with key on I believe), one is a ground; one comes from the computer, pin 19 I think - should be voltage on that one only for a second or two after the key is turned on; and the last one goes to the inertia switch and then to the fuel pump selector switch and then to the tanks.

 

Well i checked my fuel pump and when i turned the key on, i only heard one click coming from the tank, i think it was you who said before there should be two clicks....do you think the pump is bad or there is a short in my wiring??

 

Do both tanks not work? How many miles are on the truck?

 

well the rear tank went out about 2 or 3 yrs ago....now the front tank went out...i dont have time to do it so i just took it to the local ford dealership, its got about 150,000....thinking of puting in a new engine when this one goes and and just keep on truckin'

 

I'd say with 150000 miles it's about time for the pumps to fail, and I would not be surprised at all if they have failed.

 

well it was the fp.....and well i appreciate all your help EPNCSU. and everyone else's....this fourm has helped me out numerous times with my fuel pump, exhaust, and just general Ford needs....