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Old 12-16-2016, 03:35 PM   #1
dave`12
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Fuel gauge fix help pls

Hello. I have a 67 c10. All the gauges work fine except the fuel gauge. I checked, and the wire from the sending unit has continuity. Also checked the power from the harness (have a wiring diagram) that goes into the cluster that feeds power, it's good. Gauge reads empty.

Can anyone tell me how to test the sender? I had it out of the tank when I removed the tank to drain old bad gas. Perhaps I messed it up when I removed or reinstalled it.

Also is it safe to run power directly to the gauge, I'm afraid I might cook it running 12v.

Or does it run by completing a ground circuit?

The printed circuit was replaced when I refurbished the cluster, just about sure it is good.

Any help appreciated.
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Old 12-16-2016, 03:52 PM   #2
cg285
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Re: Fuel gauge fix help pls

take the wire off the sender. it should read over full, ground it and it should read empty. if it all does you have a sender issue. if not it is either a shorted wire going to the sender or some issue at the cluster
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Old 12-16-2016, 07:08 PM   #3
VetteVet
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Re: Fuel gauge fix help pls

-----------------
Quote:
Originally Posted by dave`12 View Post
Hello. I have a 67 c10. All the gauges work fine except the fuel gauge. I checked, and the wire from the sending unit has continuity. Also checked the power from the harness (have a wiring diagram) that goes into the cluster that feeds power, it's good. Gauge reads empty.

Pull the tan sending unit wire off at the fuse panel, and turn the key on first. The gauge should go to the 3:00 p'clock position. If it does then put the tan wire back on and then disconnect it at the sending unit on the tank. It should go to the 3:00 o'clock position again, but if it doesn't then the tan wire is grounded between the fuse panel and the sending unit on the tank.

Can anyone tell me how to test the sender? I had it out of the tank when I removed the tank to drain old bad gas. Perhaps I messed it up when I
removed or reinstalled it.

Refer to this thread to test the sender unit and for a complete troublshooting of the gauge and sending unit.

http://67-72chevytrucks.com/vboard/s...d.php?t=640615

Also is it safe to run power directly to the gauge, I'm afraid I might cook it running 12v.

You can put power on the gauge at the no.3 pin on the cluster plug or at the power terminal on the gauge itself but if you have already checked there with the meter you shouldn't have to.
Do not put any power on the tan wire or the Fuel terminal on the fuse panel. Those are the ground sides of the fuel gauge and voltage into the sending unit resistor could heat the resistor on the sending unit to the point that it might ignite the gas fumes in the tank, BOOM, not good.

Or does it run by completing a ground circuit?
Yes, the power goes through the gauge resistor and the gauge coils, then to the tank sending unit resistor,which is a variable resistor that changes resistance to the gauge as the float moves up and down. If you pull the sending unit out of the tank and connect the voltmeter to the terminal and the flange, and move the float arm up and down, it should vary the resistance on the meter between zero and ninety ohms. If the resistance doesn't move off zero then the sending unit is bad.

The printed circuit was replaced when I refurbished the cluster, just about sure it is good.

Any help appreciated.
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Old 12-17-2016, 04:30 PM   #4
dave`12
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Re: Fuel gauge fix help pls

Man, thanx you guys. I'm printing this up (including the link) and diving in this week.

thx again.
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Old 12-24-2016, 09:17 PM   #5
mMad Dawg
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Re: Fuel gauge fix help pls

You might also try checking the brass float. They tend to leak sometimes. Put it in some gasoline and leave it for a while. If it sinks it probably has a leak.I had to replace the one in my 69. They only cost about $5 .Good luck
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Old 12-29-2016, 03:38 PM   #6
dave`12
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Re: Fuel gauge fix help pls

thanx, all the tests show a sender problem. gauge moves as it should in the tests. tried moving the float up and down manually, nothing.

ordering a new sender, hopefully that will be it.
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Old 01-06-2017, 02:08 PM   #7
dave`12
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Re: Fuel gauge fix help pls

Fuel sender arrived. Put it in and boom, gauge works.

Without the advice on how to test from you guys, it would have been much more difficult.

thanx
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