fuel pump wiring question

purplepeopleeater · Sep 5, 2016

I've been trying to get this 87 ranger 2.9 I just picked running. Neither fuel pump is coming on with key on, truck cranks but will not start unless I squirt gas into the intake. Then it dies after its used up. Brand new relay, testing the wires from the pump relay, I get power at yellow always, red with key on, orange going to the inertia switch, never has power. Traced it and it looks preferably fine as far as I can trace it. I get no power at the inertia switch either. I've reset it and also jumped it, both get no better results. My question is, can I run a hot wire from say a spot in the fuse box that has only key on power, down to a toggle switch then to the supposed to be hot wire on the inertia switch. The idea being that it will supply the needed power from the inertia switch back to the fuel pumps while still keeping the safety feature of the inertia? Thank you for any help guys, you are always helpful and it does not go unnoticed.

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RonD · Sep 5, 2016

Remove Fuel Pump relay
Put in a jumper wire between Yellow(24/7 power) and Orange wire(to inertia switch)

Fuel pumps should now be on.

If not then Relay base may be bad or the Orange wire is.
If pumps come on then wiring to pumps is OK, problem is computer is not turning on the relay.

This relay gets 12volts(red wire) when key is ON, but has no Ground so can't close and send the 30amp power(yellow wire) out to inertia switch(orange wire)

The Computer controls the Ground to turn fuel pump relay on and off, it is usually a Tan wire with a stripe.
But what ever the color the 4th wire is the Ground for the Relay, and that runs to the computer.
You can Ground this wire and fuel pump will run any time the key is ON, better than a toggle switch, if this wire is the problem.
Or you can trace it back to computer, pin 22

No you don't want to by-pass the Relay, pump would be on 24/7.

And no you don't want to toggle switch a 30amp circuit, that's why there is a relay.

Battery------30amp fuse---(yellow wire)----fuel pump relay------(orange wire)------inertia switch--------------------Fuel pumps----Ground

If you want to replace the Orange wire, from Relay to inertia switch, that's fine

purplepeopleeater · Sep 5, 2016

Thank you for that excellent help. After pulling the in take fuel pump, I realized it was dead when I hooked direct power to it, put in a new one. Now it does the 2 second prime and seems in good order, but as luck had it, the high pressure pump is also dead. Do you know if it's common to have both pumps die? The truck has sat for several years before I got ahold of it.

fuel pump wiring question

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