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1997 Ford F-250 (Ford)
1997 Ford F-250 (Ford)

Rob's Garage

Fuel system repair suggestions for a DIY mechanic Add to ...

Hello, Rob,

We have a 1997 Ford F-250 extended cab long box truck. It has only one fuel tank, and we changed the fuel pump. When we tested the pump before we put it in the tank, it worked fine, but once we put things all back together and plugged it into the wires along the frame, it doesn't work.

The truck turns over, but doesn't fire, and when we listen, the fuel pump doesn't engage when the key is turned on. Can you make some suggestions as to what we can test to see just what the problem is?

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Thank you, Marilyn

I'm going to have make assumptions in my diagnosis based on the information you've given me Marilyn.

First, you mention that you tested the pump prior to installation. Assuming the connections were made properly, the pump ran independently of the ignition switch - that is, you simply hooked the pump to a battery.

I mention this because the fuel pump is part of a module that is controlled by the on-board powertrain control module (computer).

Again, assuming that the installation of the pump module back into the fuel tank went well, there are a few things that must be considered.

1. Grounds. Are the grounds intact? Tracking down the integrity of all grounds will require a wiring/circuit diagram to locate all of them. Often overlooked, grounds are just as important to effective electrical circuit operation as the "live half" of a circuit.

2. Electronic controls. I can only assume that the truck ran fine before the fuel pump was condemned. If not, you're looking at a full blown diagnostic process at a shop. Read: $$$

3. Inertia Fuel Shutoff Switch. Ford uses this double redundant switch to shut off fuel in the event of a collision. It may have been tripped - just like an electrical circuit breaker - but for fuel.

I have found that many starting problems with Fords can be traced to the IFS switch. It is located under the dashboard in the passenger's side footwell area, up in behind the glove box. It's about the size of a two inch square block and has a button on the top of it. The button should be in the down position to function properly. If the button appears to be sticking up, press it back down and give the ignition key a twist.

Failing that, you're on your way to your local repair shop (behind a tow truck), to have a trained technician perform a diagnostic on your truck.

Good luck Marilyn.

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