1990 Ford Bronco Fuel Pump Electrical

CBERANYK

MEMBER
1990 FORD BRONCO
V8
4WD
AUTOMATIC
182,000 MILES

I have a 1990 Bronco that will not start. Through checking everything out we have narrowed it down that it will not start because the fuel pump is not working. We checked everything else fuel filter, spark, distributor, etc. We dropped the gas tank, pulled out the fuel pump and tested it by putting the red and black wires to a battery. The pump turned right on and started working so no problem with the actual pump. Once its back in and we hook everything up nothing happens. When you turn the key to the on position (or accessory mode) nothing happens. You can't hear the pump turning on like usual. We took a circuit tester and multi-meter to the actual 4 prong plug that sends electrical to the fuel pump. The multi-meter says it has some electricity going through it but the Circuit tester never responds to it. My problem is I don't know if there is a problem with the 4 prong plug, The wiring to the plug, or the actual housing of the fuel pump that has the wires and float attached to it. My question is what else can I do for testing what the problem is? Can I plug a code scanner in? Would that device find a problem in the wiring? Any suggestions would help since I am completely stuck. Thank you

3 Replies

MATHIASO

MECHANIC
1,209 POSTS

These trucks employ a single, high pressure pump which is part of the modular, In-Tank Reservoir (ITR) assembly. Besides the pump, the ITR consists of a venturi jet pump, a supply check valve and a shuttle selector valve. All this is mounted on the fuel gauge sender flange. The sending unit is separate from the ITR module.

Two electric pumps are used on fuel injected models; a low pressure boost pump mounted in the fuel tank and a high pressure pump mounted on the vehicle frame( the one may not been tested).
The low pressure pump is used to provide pressurized fuel to the inlet of the high pressure pump and helps prevent noise and heating problems. The externally mounted high pressure pump is capable of supplying 15.9 gallons of fuel an hour. System pressure is controlled by a pressure regulator mounted on the engine.
there may be 2 pumps, am I wrong? wich one you tested?

high pressure pump

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Saturday, October 31st, 2009 AT 5:14 AM

CBERANYK

MEMBER
2 POSTS

We tested the fuel pump that is inside of the gas tank not the one that is mounted to the vehicle frame. The problem is the electrical to the pump inside the gas tank. I am reading on other forums that there are recievers ( a couple of them) A shut off switch under the dash and a couple other things that will control the electrical and I am not sure were to start or what else could be causing the electrical not to go to the fuel pump.

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Sunday, November 1st, 2009 AT 11:48 PM

MATHIASO

MECHANIC
1,209 POSTS

If there is power at the inside pump connector and the inside pump does not work, replace the inside pump.
If you need instructions to removing and installation of the inside pump, let me know.
If the inside pump works and the one mounted on the frame does not works, fuel will not reach to the regulator. If there no fuel at the regularor, fuel won't be at the injectors.
I can't find or there is no inertia switch on your bronco, the switch that shut off the fuel pump when there is accident or when dry out of gas?

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Monday, November 2nd, 2009 AT 2:28 AM