I recently got a non-running 1987 F150. The gentleman I got the truck from mentioned that the rear fuel tank would mysteriously overflow the front tank, so he believed the FSV was malfunctioning. I have bypassed the valve and replaced the fuel filter but can't seem to get the truck started. I have checked to see if the high pressure pump is working properly and it is. I have also checked to see if the in-tank pump is working as well and it is. I have tried using starter fluid to see if the truck will run and that was successful. However, after the fluid burns out the truck stalls and quits running. I admit I'm not the most mechanically inclined person I know so I need all th help I can get. Anyone have any suggestion? I'm all ears!

 

Do the fuel pumps run all the time the key is on?

 

Have you checked to see if fuel comes out at the fuel rail schrader valve?

Do you hear the high pressure fuel pump kick on when you go to turn the key?

 

Thanks for the replies guys! When I turn the key to the on position I can hear the high pressure pump kick on. I have yet to locate the schrader valve on the fuel rail, I think it is behind the engine out of reach. If I'm wrong feel free to correct me.

Thank for the input,
Ty

 

If you are saying the pumps are running all the time the key is on and the engine is not running then I would say a bad EEC Computer.

What size engine do you have?

 

I have the 4.9 L6. The previous owner changed the EEC before I got it but he saved the old one. Yesterday I got the old one and installed it and the truck made an attempt to run but that was about it. Do you think the original could be bad as well?

 

Not sure, do the pumps run all the time the key is on with the old one?
Do you have no spark with the computer installed and you have spark with it out?

 

Hi Bill, Sorry to take so long to get back with you. To answer yout question, I do get a spark with the installed computer. The pump which is bolted to the frame runs for a few seconds when the ignition is turn to the on position but seems to stop. I located the schrader valve and it released no pressure at all. I have changed the fuel pump relay thinking that might rectify the issue, but it didn't. Do you think the fuel pump is bad?

 

Sounds like the computer and frame fuel pump are OK for now and your old fuel pump relay was good.
The frame pump is only to run for one second when you turn on the key and do not crank the engine.

To test the fuel system you need a paper clip, a test light, a 5 Gal bucket and a fuel pressure gauge (can be rented at most auto-parts stores).

First jump the self-test plug on the drivers fender pin #2 to #6. (image below)
Turn on the key but do not crank the engine.
The frame pump should run and the selected tanks pump inside should run as well. Listen at where you put the fuel in or under each tank.
If you do not hear the selected tanks pump run hit the bottom of the tank with a rubber hammer and see if it starts. If still no go try reversing the wires to the pump to see if you can break it loose then revers the wires back, if not then check for power on the power wire to the pump with a test light.
If you have power at the plug and the pump still does not run then change out the tank pump.

If you do not have power on the pump wire than check for power going in and out of the selector switch.

If both fuel pumps run (the frame and selected tanks) then turn the key off and hook the fuel gauge to the fuel rail. Do not let the frame pump run for more than 5 minutes at a time with no fuel as it uses fuel for cooling and you can burn it up.

Turn on the key and see if you get any pressure on the gauge with pin #2 to #6 of the self-test plug shorted.

If no pressure on the gauge with both pumps running turn off the key, pull the hair pin out of the supply fuel hose coming from the selected tank at the input of the fuel selector valve and pull the hose off and stick it in the bucket. Have someone turn on the key and see if you get a steady flow of fuel out of the line, if so turn off the key and put the hose back on. Then take the pressure supply fuel hose leaving the selector valve off and stick on a short piece of fuel hose and aim it in the bucket, turn on the key. Fuel should come out of the valve if not replace the valve. The pressure from the tank pump should be from 7-12 PSI.



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