Fuel pump problem

[MUDDING B-3000]

well ive been tracing wires trying to find out why the fuel pump wont get 12V an turn on, ive followed the wires to the fuel pump relay an its got 12V at all the terminals except on the wire that runs to the inertia switch then to the fuel pump? i figured the problem was the relay so i replaced it an it still doesnt work?

the guy at the parts store said it could be another relay that also send power to the computer an then again to the fuel pump but i dont kno?

also the pump does work because when i take the relay off an just jump the the wire that goes to the inertia switch then to the pump it will turn on.

 

[nitrofan1]

Check the voltage to the inertia switch. If you haven't found it it's at the bottom of the dash right at the trans tunnel in front of the shifter under the carpet. Check the voltage going to and from the switch. If both the wires have 12v you may have a bad inertia switch. Of course check to see if the switch isn't tripped.

I had the same problem 3 weeks ago, even having it towed to my mechanic. The tow truck driver got to my truck, put the key in, started it right up and drove it onto his flat bed. The shop never got it to "not" start and the problem never came back. After some research it could be an issue with the puter. It's a long shot but try the inertia switch voltage. If it is bad Advance has the switch #S9300 for $75.99.

 

[MUDDING B-3000]

ive checked that an im not getting any power to the inertia switch, thats why i thought it would be the relay not opening. which would not send 12V to the inertia switch.

 

[nitrofan1]

Hmmm, well on the power distribution box where the relay is you should have 3 identical relays. I have swapped them in the past to eliminate the relay. If the new one & tryin swapping won't work there is a small chance the relay board may be bad. That is a last resort try. Course if you are good with wiring you may try to move the relay & wiring to an empty relay plug which you should have a couple on the board.

 

[MUDDING B-3000]

what do u mean by the relay board? like the brackets under the fuse panel that hold the relays? do those metal prongs that hold the relays like ground them or something? cuz i have mine out of that an there just sitting there so i can take readings with the mutli meter an crap?

 

[MUDDING B-3000]

i heard that it could be something with the eec relay or something? how can i check that its sending power to the fuel pump relay?

like when the ignition is off i have 12 volts to one of the 4 wires an when i turn the key to on i get 12 v to 3 of the 4, an the one with NO power is the one that runs to the inertia switch?

 

[rags]

An easy way to see if the EEC relay is working is turn the KOEO ( key on engine off ) see if the check engine light is on. If it's not on the puter has no power and will not turn the fuel pump relay on. If thats the case try switching the EEC relay with the A/C Relay and see if it works.

This happened to my 94 and was an easy fix.

 

[AllanD]

The EEC power relay, the Fuel pump relay and the A/C WOT cutoff relay all use unique connectors on an '85-92.

It wasn't until the switch to the larger load center box in 1993 that the relays plug in from the top.

He's working on his 1992.

his 1994 would definatly be easier to deal with.

That large load center with the top mounted relays is why I
used 1993 Explorer wiring when doing my 4.0 swap

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[MUDDING B-3000]

ok so if i do what rags said on my 92 will that still tell me if the comp is getting power? this is the last thing i need to figure out before i can drive this monster well then i just need a new re driveshaft but i can finally hear the thing run.

 

[BillupsOMally]

Don't know if I'm missing something, but you said with the key ON you have power to 3 of the 4 terminals??

1 terminal is always hot.
1 terminal goes to the fuel pump.
1 is power from the computer.
1 terminal is GROUND.

Without that ground there's no way the relay can energize.

If there's a wiring diagram of the relay on the side of it that makes life easy.
If not.. there should be 2 larger pins on the relay, and 2 smaller ones. The 2 large ones are for the fuel pump, and the 2 small ones are for the energizing circuit in the relay.
One of those small pins needs to be a ground, sounds to me like you might have a simple wiring problem.

Good luck.

 

[MUDDING B-3000]

ok thanks ya some one was telling me it might be a grounding problem so ill have to check it out tomorro thanks alot i think you just helped me fix the problem lol.

 

[BillupsOMally]

No problem.

Let us know how it turns out, follow-ups are always nice.

 

[MUDDING B-3000]

i got it all fixed, it wasnt grounding properly

thanks for all the help.

 

[bit]

Where was the ground problem?

 

[MUDDING B-3000]

it was a plug that came off the neg terminal of the battery that i guess was the grounds for all the relays cuz they all work propertly now lol