fuel gauge problem

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Jun 13, 2006 | 01:32 PM

Ron McCafferty

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fuel gauge problem

Working on a 96 PS with a fuel gauge that reads past full all the time. Does anyone out there have any idea where to go to get technical assistance, wiring diagrams or diagnostic charts besides the dealer?

Jun 13, 2006 | 01:58 PM

Cuda_jim

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From: MICHIGAN

There is a member here 1997f-350 that has a link to service manual online in his signature.

The link says "got manual", click it. Should help.
CJ

Jun 14, 2006 | 06:49 AM

Ron McCafferty

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Thanks CJ. I think I know who you are talking about. I appreciate the info.

Jun 15, 2006 | 12:48 AM

bodabdan

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From: River Valley AR

Sending units in the tank work by varying resistance. If you can locate the wires going to th seding unit you can open and short the wires to simulate very high (infinite) resistance, and very low resistance. If th egauge responds by going from one extreme to the other your gauge is probably working and I would suspect the sending unit.

Jun 15, 2006 | 06:13 AM

Ron McCafferty

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Thanks for the info,guys. This one is driving me nuts. I don't think it is a problem with the sending units. I checked them with my meter and the the resistance values were right on the money. The wiring to the switching valve and sending units is good. The only thing I can figure the instrument panel is shorted somewhere. I had the switching valve/sending units unplugged and the gauge still went up passed full when I turned the key on. Funny thing is I've got 12v, a good gnd and the signal wiring all the way back is good. I may try swapping IP's with my own truck to see if that fixes it. Thanks again.

Jun 15, 2006 | 12:32 PM

bodabdan

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From: River Valley AR

Can you jumper some wires across the switching valve and run the signal from the sending unit straight to the harness that goes to the gauge? The point of this would be to take the switching valve out of the circuit and see if it makes a difference or not. It's possible that there's a problem with the contacts inside the valve, and this check could confirm that.
Has the instrument panel been removed lately? check for loose electrical connectors in that area and along the harness.
When you unplugged the valve the gauge stayed at full. That makes me think that an open curcuit would cause the gauge to read full, so a closed circuit should make it read empty. If you short the wires together and the gauge still reads full you may have an open circuit between the valve and the gauge. Continuity checks from the gauge to the valve should show this.
I also think there's a good chance that the gauge itself may be bad but I would try all the tests first if it could save some $$.

Jun 16, 2006 | 10:30 AM

Ron McCafferty

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I did't take the signal wire out of the loop but I think I should. Even though I check it for short to voltage I didn't check it for short to ground which would peg the gauge. Thanks for your info. Sometimes when I get frustrated I over look the simplest things.