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Discussion Starter #1
I am having problems with the fuel gauge. It is an Autometer 0-90 ohm gauge. I am not sure what the problem is and yes I have searched several post and looked at the stickys. I have a new sending unit in the gas tank and a new ground from it. After hooking it up it has worked fine for several months then all of a sudden it is pinged all the way to empty all of the time now. If I disconnect the sending wire it pings all the way to full. If I ground the sending unit wire it pings it all the way to empty again. I would think that this meant the the sending unit wire is grounding out somewhere but I checked and it is fine. Anything else that I am missing? thanks
 

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The only place in the harness you could conveniently disconnect the tan wire is in the trunk.

With the tan wire disconnected, you should be able to read the fuel level in ohms, full = 90 ohms, half tank = 45 ohms, fourth tank = 22 ohms wityh one meter lead to the wire and the other meter lead on a good ground.

If you read very low ohms or a short to ground, then the tan wire from the trunk floor to the sending unit has its insulation worn through between the trunk floor and tank.
 

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Discussion Starter #4
most of the time when a sending unit is bad it would peg out. it seems to me you might have a gauge problem
Is there anyway to check the gauge to see if it is the problem? I thought if it would sweep each way then it was working?
 

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same concept on gauge as in sensor. if sensor is working and is not then you think wiring. but if wiring is good, then gauge is bad, it has to read same way sensor does
 

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you tested the guage in your first post. Disconnect tan wire in trunk guage reads above full, ground tan wire (not tank side) in trunk reads below empty. Everything in front of the test point is good. The problem is between where you tested and tank. I think Everett is on the right track, wire shorted between tank and floor.

Jeff
 

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Discussion Starter #7
you tested the guage in your first post. Disconnect tan wire in trunk guage reads above full, ground tan wire (not tank side) in trunk reads below empty. Everything in front of the test point is good. The problem is between where you tested and tank. I think Everett is on the right track, wire shorted between tank and floor.

Jeff
The tan wire from the sending unit to the first connection in the trunk is new also. My ohm reader when checked from just the tan wire disconnected in the trunk shows the ohms jumping all over the place, they will not stay at a solid number? I am grounding it at a few different places and it is the same. I hope it is not the sending unit again, I just replaced it. looks like I will have to drop the tank again. i hope my ohm reader is working correctly, maybe I should try another one. Can anyone suggest a good one?
 

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If it's one of the $49.99 repro sending units, it may be bad. My cheapy unit was bad out of the box.

In a 69, it is easy enough to stick a clothes hanger rod or something like that in through the filler neck to move the float up and down and see what happens.
 

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Discussion Starter #9
If it's one of the $49.99 repro sending units, it may be bad. My cheapy unit was bad out of the box.

In a 69, it is easy enough to stick a clothes hanger rod or something like that in through the filler neck to move the float up and down and see what happens.

Is it pretty easy to tell when you hit the float? The sending unit was from classic industries, it was like $100.
 

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I just used a mini mag lite to shine in and see the float, then hooked it with the clothes hanger. It should be just a little left of center; my float was black, which made it easier to see. Just don't snag the filter sock.
 

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If you determine that it is the sending unit I suggest going with the Spectra Premium unit. I got mine from the local auto shop. I see others have posted they got theirs from NAPA p/n FG104C that is for the single 3/8" line. I have have one in mine and have had no problems.
 
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