2.3L ('83-'97) Fuel pump relay problem

[Cyndiluwhoo]

Have problem with loose fuse box tree and faulty wiring under the fuel pump relay. Driving it causes wiring to move and wont start after shut off. We even tried the bypass test. We can get it cranked but not without manipulation. Should i try to replace the whole box tree stand ? Dealership said they cant get the part so it will have to be a salvage part.

 

[RonD]

Welcome to TRS

Not sure what you mean by "fuse box tree", is that the bus bars in engine fuse box?

Have you pulled up the engine fuse box to look for corrosion on the under side?

Fuel pump power path thru FP relay(relay pins 30 and 87/3 and 5)
Battery-------20amp fuse----FP relay--------------inertia switch-------------------------fuel pump----ground

FP relay activation(relay pins 85 and 86/1 and 2)
Battery---30amp fuse----PCM relay------FP relay----------------------PCM(computer)----ground

FP relays coil gets 12volts with key on when PCM relay closes, PCM relay also powers the computer(PCM), fuel injectors and most 12v solenoids like IAC Valve and EGR

The PCM then Grounds the other coil connection to activate the FP relay for 2 seconds, and 2 seconds ONLY, when computer boots up
It won't activate again until engine starts, above 400rpms, its a safety thing
But turning key off and then on again will get another 2 second activation, each time key is switched off and then on

 

[tomw]

Re-wiring so the fuel pump connections are external to the fuse box would be a possibility, but a lot of work. You don't want to mess with the safety stuff designed into the system, and removing that circuit from the box would involve connecting to the conductors underneath the fuse box plastic.
If you can find a good used unit in a boneyard, that would be a feasible solution.
If the problem is corrosion underneath, a replacement seems like a good way to avoid future problems.
If the problem is bad connectors for the fuel pump relay, some 'surgery' could be done to replace just those connectors, though I have not looked. Sometimes using some small nosed pliers, the connectors can be re-bent to apply tension to the relay terminals and a good connection. You have to use your judgment as to which way to go.
One other possibility is to solder a relay terminal block(4-5 terminal socket) to the conductors under the fuse block and leave the relay socket above the rest of the relays and fuses, on top. You would then plug the relay into the relay socket.
tom

 

[Cyndiluwhoo]

We finally found a repacement in a salvage yard. Not sure if i can find someone to solder it. Thought about just doing a cut down and rewire to replace the whole thing. Havnt touched it yet.

 

[RonD]

Ford used external PCM(EEC) and Fuel Pump relays until the late 1980's, early 1990's

Nothing unsafe about it