Question fuel guage reads way over full

ward cleaver · May 28, 2008

My fuel guage is reading way over full on either tank. (front tank's empty and back tank's half full.
I checked the wire connection at the fuel tank selector valve (looks good).Where else should I look? This sucks when you don't have much fuel in your tank.

bushpilot · May 28, 2008

Hummm if it were just one tank i'd suspect it to be the sending
unit...doesnt seem likely that BOTH sending units in BOTH tanks
are bad.

just thinking out loud here but generally if the resistance is LOW
the tank should show full...in your case it sounds like the resistance
is close to zero<pushing the needle past full> ...knowing this id be
looking for a SHORT <to ground> between the gauge and the float(s).

unfortunately in your truck i dont know how the switch plays into
the gauge set up... sorry...

ward cleaver · May 28, 2008

I got a schematic of the circuit and it says it should read 145 ohms full and 22.5 ohms empty.
I'm thinking it's a loose ground somewhere?

johndeerebones · May 30, 2008

ward cleaver said:
I got a schematic of the circuit and it says it should read 145 ohms full and 22.5 ohms empty.
I'm thinking it's a loose ground somewhere?

A loose ground would have more resistance, if you have access to a signal generator that would be great, or you could go to radio shack and but a bunch of resistors and pots to make your own that runs in that ohm range....

BlueMule · May 30, 2008

ward cleaver said:
I got a schematic of the circuit and it says it should read 145 ohms full and 22.5 ohms empty.

That's right, so a break in the wire would cause the gauge to read past full.

Pin # 5 on the fuel selector valve is a yellow wire with a white tracer, check it for continuity between the valve and the gauge.

Question fuel guage reads way over full

ward cleaver

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bushpilot

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ward cleaver

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johndeerebones

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BlueMule

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