Hello and I am located in San Antonio, TX. I have a 1993 F150 extended cab, with 5.8 and a E4OD. This forum is great and has helped with a few things before. Now I have a problem I can't figure out. I have replaced the rear tank fuel pump assembly due to the fact the truck bogged pretty bad when stepping on the gas. That problem is solved. Of course I did not read the instructions (LOL). Truck runs good off that tank but the fuel gauge always reads full. I went bad and read the instructions and it says you have to change the supplied pigtail on the truck side of the wiring. Only 4 wires no big deal. Easy right, well wrong. Swapped out the pigtail, and the truck will not start off either tank now. I have checked for spark and it is fine. I can start the truck with starter fluid. I know it is getting fire, but no fuel. I cannot hear the pumps when you turn the key on. I have checked the fuel circuit breaker, it is not popped. I have checked all the fuses and relays. All seem to be good. I can switch from front to back on the tank selector and watch the gauge move. So that seems to be working properly. I am out of ideas. Anyone have any ideas. Could it be the computer.


Thank you,
Mark

 

To start with a pegged full fuel gauge means an open circuit to ground when the selector switch is switched to the rear tank.

Does the fuel pump relay click when you turn the key to on and drop back out one second later each time you turn on the key?

I have not heard of adding a pig tail to the fuel delivery module when changed out on a 1993 F150. The only pig tail I know of is for the new stile turbine fuel pump on the F53 chassis.

 

I vaguely remember having to do a pigtail swap when replacing the sender/pump in my 92 F150 a while back. I'd re-check those new connections first. It sounds like the signal to run the tank pump isn't getting back there. could be as simple as a wiring glitch.

 

I do not hear the relay clicking. also if I switch to the front tank it does not start either. And no clicking of relay.

 

Then turn on the key and ground pin #6 of the self-test connector and see if the fuel pump relay clicks as you ground and in-ground pin #6 of the self-test connector.


You can also try to jump between pin #2 and pin #6 of the self-test connector but try grounding pin #6 first.
pin #6 of the self-test connector.



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Thanks I will try that today when I get home. If the relay clicks when I ground pin #6, then the relay is good. Correct. Also what should happen when I jump pin #2 and pin #6.

 

Check the FP fuse. Did you disconnect the battery when you rewired? May have shorted out the circuit with power going to it.

 

I have checked all the fuses and they are good. Yes I did disconnect the battery first.

 

I assumed you did. Hope it didn't come off as insulting.

 

The fuel pump fuse as no bearing on if the fuel pump relay clicks or not.

 

You might also check if the PCM Power relay clicks each time the key is turned on.
As the PCM Power relay must be made (closed) before the fuel pump relay will close.

 

How can I check the PCM power relay. Sorry for all the questions.

 

The PCM power relay supplies power over red wires to all the fuel injectors beside the fuel pump relay coil and other solenoids.
So with the key on check for power at any of the fuel injectors red wire with a loading test light.
If the test light lights the PCM power relay is closed.

 

Awesome, thanks. I will try that tonight too.

 

OK checked the relay using key on and jumped#2 and #6. Relay clicked. Also with key on used test light on red wire of the injector. It lite up. So at the point I would assume the relay and computer is good. Now I am really lost.