Intermittent fuel gauge stuck on full

J GOWE

MEMBER
1987 FORD F-150
5.0L
V8
2WD
AUTOMATIC
118,000 MILES

Fuel gauge pinned on full but some times seems to work. Anyone have any idea where to start to solve this problem?

Monday, May 18th, 2020 AT 5:29 PM

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Do you have dual tanks and I assume if you do then both tanks make no difference?

If so, I attached the wiring diagrams. We need to test voltage coming from the selector switch. You have a number of inline connectors that could cause an intermittent issue. However, the always being on full indicates a short to power. Basically this gauge works off of voltage. The more fuel the higher the voltage which raises the gauge.

Let me know if you have questions. Thanks

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Monday, May 18th, 2020 AT 5:59 PM

J GOWE

MEMBER
6 POSTS

We do have dual tanks. We don't use the back tank it is fouled. We only had the truck a week and she sat for 6 years.

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Monday, May 18th, 2020 AT 6:26 PM

KASEKENNY

MECHANIC
18,907 POSTS

Okay. Then let's treat it like a single tank. Check voltage on the yellow wire with the key on and see what it is telling you. If it is battery voltage then I suspect the fuel gauge sender has failed. Let me know if you have questions. Thanks

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Tuesday, May 19th, 2020 AT 4:53 PM