No power to fuel pump

TRX4

MEMBER
1994 FORD F-250
5.8L
V8
2WD
AUTOMATIC
120,000 MILES

Truck has no power to the inertia switch, duel tank selector or the fuel pump. The fuel pump relay clicks when the key is turned on. How would I trace this?

Friday, September 20th, 2019 AT 7:34 PM

6 Replies

JACOBANDNICKOLAS

MECHANIC
108,133 POSTS

Welcome to 2CarPros.

Check the fuse which powers the switch and relay. I attached a picture of it. If the fuse is good, check to see if there is power to it.

Next, you will have to check at the PCM pin 8. I attached a picture of that also.

Let me know what you find.

Joe

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Friday, September 20th, 2019 AT 8:34 PM

TRX4

MEMBER
4 POSTS

Okay, power to and out of the fuse and power to the green wire(with yellow tracer on pin 8).

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Saturday, September 21st, 2019 AT 8:06 AM

TRX4

MEMBER
4 POSTS

But still no power to the inertia switch.

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Saturday, September 21st, 2019 AT 7:51 PM

JACOBANDNICKOLAS

MECHANIC
108,133 POSTS

Welcome back:

Then either there is a break in the wire itself or the splice has lost its connection due to corrosion, vibration, age, and so on. I circled the splice in the attached picture. You will need to trace that wire from the inertia switch back until you locate that splice. I suspect that is where the problem will be.

Let me know.

Joe

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Saturday, September 21st, 2019 AT 10:07 PM

TRX4

MEMBER
4 POSTS

I’m dumb. There actually was power to everything. I thought leaving the key on would show power but there is only power for a couple seconds after the key is turned on (to pressurize the fuel system). There was power to the pump. I changed the pump and still it wouldn’t work. It turns out it was the fuel pump hanger causing the trouble. The four wires enter the top of the hanger assembly and must be corroded because I tapped on them with a hammer while someone turns the key and the pump ran and the truck started. So I will change the hanger assembly. Thanks for your help!