I have a 1990 f150 4x4 5.0 with duel tanks. truck won't start.I was told that I needed a fuel pump but I couldn't see 2 pumps going up at the same time.
then I noticed that the FP relay wasn't kicking in so I replaced it, still the same thing. I don't want to replace fuel pumps until I can get the FP relay working.
If anyone can help me I would really appreciate it.

 

There is a frame pump also check that it might be out. There is a fuel pump thread in this section. Check it out by typin in fuel pump trouble in the search box.

 

My book says that there are only have 2 pumps 1 in each tank. I looked and cat'n find a 3rd pump. Is there anyway to jump the FP relay and go straight to the pumps just to see if they pump. I would to thank you for your help.

 

I know older trucks, pre '87 had the 3 pumps. Low pressure pumps in the tank(s) and a high pressure pump on the frame rail near drivers door and in front of the selector valve. Ford may have deleted the frame pump and now use in tank HP pumps?

Note that the EEC turns off the pumps after 3 or 4 seconds via FP relay if the engine does not start for any reason.

Also with the older trucks there is a pump pin in the OBDI connector which you can ground out to force the pumps to stay on. Make sure the tanks are not totally empty before doing the jumper.

Or you could have someone switch the ignition on and off while you listen for the tank pumps.

 

I would to thank you for all your help. I think I know what you are telling me. I think I have to put a jumper from the A terminal to the E terminal and that should force the fuel pump relay on. I hope I am rite. let me know if you think I'm rite. I have already listened for the pumps to come on and neither one comes on and I don't think they will if the FP relay doesn't click on.

 

Is your inertia switch popped?

 

X2

 

x3 thats what i was thinking.

 

You need to do a voltage check at the relays,the Ecm relay is what activates the the pump relay so check it also.

 

My book says the inertia switch is under the passanger kick plate but its not there. is there any other place it could be. I will try to get the voltage checks done as soon as posible. I am going to try to jump the pumps on using the test terminals as soon as i get a chance. please be patiant with me and thanks