fuel pump power

[wilsbronco]

I'm a new owner of a 1981 bronco, frankenstein version. It's current engine has 40k miles and is fuel injected. The fuel filter and pump are underneath on the rail, as in later Ford models. It had been sitting for probably a year. We put a new battery in, it turned over and started right up first try, ran for a few seconds (sounded strong), then died. Now it turns over but won't start. Its not getting fuel. We replaced the fuel filter, pulled the pump (looks fairly new, so we put it back in for now). Confirmed in the engine compartment that no fuel is getting there (there IS gas in the tank). Multimeter says that there is no power getting to the pump. I can't find the intertia switch as its not behind the brake pedal by the firewall in the passenger compartment where its suppose to be. The hot wire for the pump I've traced into the engine compartment into a mass of wires that are near the steering column. I think I might see it coming out and going towards the drivers side where it appears to be plugged into a relay with a few other wires (not completely sure, but there is another red wire of the same guage going there).

Any educated guesses as to where I might start hunting for the inertia switch, if it indeed has one? Any relays to look at?? I've checked the fuse panel and all fuses are intact (although there's an open slot that looks like maybe a fuse SHOULD be somewhere and isn't). Any other suggestions??

THANKS!

 

[Seabronc]

An 81 didn't come with EFI, so if it is installed at all, it could be any where. I'd take a meter and work back from the pump tracing the wire. If the switch is installed it is between the relay and the pumps. Do you have 12V coming in and out of the relay to the wire for the pumps? Have you tried changing that relay? Do you have 12v to the coil of the relay?

Good luck,

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[BIGWILL-5811]

I just replaced the whole fuel system on my 88 351, like the other guy said trace your power from pump forward. undo the fuel line at the high preasure pump and turn the key, do you have fuel there? do you have a fuel resivouir unit? that was my whole problem, it had a resivouir with a bad gasket in it.. good luck.. oh did you check for proper direction of flow on pump, filter? and did they install an inertia switch??

 

[wilsbronco]

I traced the wire from the fuel pump directly to a relay in the engine compartment. After running some test wires from the pump directly to the battery, the pump ran and so did the engine. I got a new relay which got juice to the pump, it did have a bad ground so I rehooked up my temp wire from the negative straight to the battery. Everything ran for a few minutes before it killed. No power at the pump again. As the original relay did not have any numbers, the parts store was guessing and gave me one that looked the same.

Do I have the wrong relay? Probably another problem further upstream?

Thanks for the help so far! It's very much appreciated.

 

[Seabronc]

I traced the wire from the fuel pump directly to a relay in the engine compartment. After running some test wires from the pump directly to the battery, the pump ran and so did the engine. I got a new relay which got juice to the pump, it did have a bad ground so I rehooked up my temp wire from the negative straight to the battery. Everything ran for a few minutes before it killed. No power at the pump again. As the original relay did not have any numbers, the parts store was guessing and gave me one that looked the same.
Do I have the wrong relay? Probably another problem further upstream?

Thanks for the help so far! It's very much appreciated.

A stock EFI has an EEC relay that supplies the 12V to pick the pump relay. Power for the pumps should be coming via a fuse to the relay and then to the inertia switch (which you don't seem to have) then to the 2 pumps. I would suggest that you wire in an inertia relay. It is there as a safety device to shut off the pumps in the event of an accident, nothing like fuel being squirted all over after an wreck.

Good luck,

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[wilsbronco]

I agree that wiring in an intertia switch is the right thing to do, and I plan on it after I get the thing running. Nothing wrong with being safe! In the meantime, I've used the multimeter and believe that the new relay is just fine. It's a problem further upstream. The control wires going into the relay turn the pump on for about 3 seconds when the key is turned into the "on" position, then it cuts off. According to the Haynes wiring diagram for an 87 FI (which ~may~ be what is living in my 81), the fuel pump relay is fed from the EEC relay. Does anybody have an idea what could be causing the signal to turn off after just 3 seconds?

Thanks again!

 

[Seabronc]

Here are a couple of diagrams from the 89 EVTM that might help. IF, yours is hooked up this way, then there are two more possibilities. On the page 40 diagram note that the ground for the fuel pump relay is controlled by the EEC, (not sure what it bases control on).

Any way, I'd check the red lead on the fuel pump relay for 12V on the fuel pump relay and watch it to see if it remains there after the engine cuts out. If the 12V cuts out, then I'd suspect the feasible link that supplies power to it, jumper around temporarily to see if it the truck will continue to run.

If the 12V remains, then check to tan with light green wire to see if the ground is OK. If the ground disappears, temporarily jumper to see if the truck continues running. That would suggest a EEC problem or possibly some sensor. The EEC control of the fuel pump in a Diesel will shut off the pump if oil pressure is too low, (not sure where your EEC came from, so it may do the same).

Good luck,

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