90 BRONCO NO POWER TO FUEL PUMP

[BroncoJoe19]

I've replaced the grounds that are directly associated with the power supply, right off the wiring harness.
A. Starter mounting bolt - replaced ground

B. Right front of Engine compartment near the battery - replaced ground

C. Lower left front of engine

D. Right front of engine compartment on upper radiator support. - replaced ground

E. Left front of engine compartment Upper radiator support - replaced ground

F. Bottom of cowl panel

G. Rear of left fender apron

H. Behind bottom of right cowl panel

I. Left rear corner of cargo area near rear lamp assembly

J. Under center rear of vehicle on rear cross member.

My wife was driving the thing when it quit. There was a raised bump in the road and when she went over it the vehicle was jarred slightly and just quit.

Thanks for the continued help.

Check ground G.

You said in your initial post that you have low voltage to the inertia switch.

If I am reading the wireing diagrams correctly,

you should have 12 volts from the fuel pump relay DK green-yellow wire to the inertial switch, and then from there by way of a red wire 12 volts to the pump.

At the pump, both the black and the orange wires should be grounded.

Does your fuel guage work?

It appears that the black wire is for the fuel gauge sending unit and the orange is for the pump.

You mentioned that you changed the fuel pump relay. Are the connections there clean? And do you have 12 volts going to it?

 

[Big_Ford_POS]

Alright now I had this same problem, so forget all this ground crap for a minute and listen up... After you try what I tell you then go back to chasing ghosts... Now get your meter and your wiring diagram and make a jumper wire no longer then a foot. Get a box of fuses cause if your clumsy your gonna burn a few. Before you do anything, pull your fuel pump relay and check all the wires coming into it. (very inportant... casue my problem was a corroded connector inside the relay plug that finnaly broke, but it stayed inside and would occasional make connect and **** me off, it finnaly died for good at a red light, leaving me to block traffic and then get towed for 60 bucks.) Pull on all your wires and look up inside the back of the plug with a flashlight buy don't break the connector. The ford dealer sells a new pigtail with wire that you just splince back on. Now if that is all good find your fat wire that is supply power ( two thin wires just activate the coil in the relay when the EEC relay tells the fuel pump to come on). The wire your looking for is all time power weather the key is on or not (yellow 37 according to the diagrams on the post). If you have power there then use your jumper wire to take power from that to the wire that goes to your pump. (Use your diagram to find out which one that is {Brown 276}) If you do it right then your fuel pump should come on. If it comes on then your problem is not ground or the in the pump or even at that end of the truck. If it doesn't come on sucks to be you.... If it comes on then turn over your truck and it should run.

Now the second problem is why doesn't the relay get told to come on. Try the above and see what you come up with.... then report back....

 

[dramin]

I am having a similar problem to my 93 bronco 5.8l 351 full size, when i turn on the ignition the fuel pump does not turn on. I have replaced the fuel pump fuse and fuel pump relay, they both have 12v going to them when the ignition is on. I initially thought it was the fuel pump because i checked for juice down at the pump and i had hot so i replaced the pump only to find that the pump works fine. later checking i found that i only have 3 volts on 1 wire (yellow) which is obviously not the power to my pump. I am thinking i have a bad ground on the relay, does anyone know where that ground is? its too hard for me to trace the wiring from the power control box because my haynes manual doesnt have correct wiring colors and theres a shitload of wiring on that harness there and i dont want to tear it all up. my inertia switch also only has 3volts going to it through the dk grn/yellow wire and neither of the other 2 wires are hot when i disconnect the plug and check them. If anyone knows where my fuel pump relay is grounded id love to know or has any other ideas about what could be causing me to be getting no electricity to my fuel pump lemme know!

 

[PonyXpress]

Look at the previous posts on this thread for wiring diagrams posted by seabronc and ground locations posted by broncojoe.