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Keep in mind, I'm a woman and learning as I go out of neccesity (no $).
I think I have a rough idea what the EEC does - but haven't been able to find the answer to my question anywhere else.
If the wiring on the EEC is afu, would that cause both fuel pumps to quit on a 1990 f350?
I have changed the fuel pump regulator. I changed out some fuses and fixed a short. Still neither fuel pump primes when I turn the key. I have a wiring issue on the plug that plugs into the EEC module.
The computer grounds the pumps to make them run, if you have doubts thats working you can test the pumps by passing the EEC.
Locate the EEC test port, hold it in your hand so the long flat side of the connector is down, turn the key to "run" then ground the far right bottom wire in that connector, use a short piece of wire to ground it with. If the pump relay works and has power to it the pump/s should run, test one then switch tanks and test the other.
If the pumps are found to run with the test then find the right wire at the EEC connector (Dark green/yellow? - EEC connector pin #8?), test it for continuity from the EEC connector to the pump connector at the tank. If no continuity find the short, or run a new wire in its place. If you run a new wire you must do so as to be weather tight. Hard to do under a truck so keep that in mind.
Scroll down to see EEC connector showing pin number locations.
My bet is the fuel pump relay or its connector. Try wiggling the wires at the connector. If it starts working you can a get replacement wiring pigtail. I've seen a lot of pre-92 trucks with corroded fuel pump and EEC power relay connectors causing this kind of issue.
Where the wires go the the fuel pump relay - those look to be in good condition. The wiring to the EEC - the spot where the 2 wires go into 1 spot (I know, I am so technical . . .) they have become severely corroded. So corroded that when I tried to clean them up they broke off. I stripped the ends and cleaned up the ends of the wires but . . . . how the heck do you hook them in? I can splice and clamp wires - better if I get a new pluggey-thing with the wires comming out and splice them into the existing wiring? Two wires into one spot. . . one for each fuel pump?