fuel gauge problem

[cjoenny89]

can anyone help me out with the fuel gauge? when the truck key is in the off position the fuel gauge reads 1/4 tank when you start the truck up or turn the key to the on position the fuel gauge goes to empty. I know its not empty.
It appears to have only one wire going to the tank could it possibly be I have a broken wire or a wire that is grounding out? Or could it be the sending unit?
any suggestions would be great. I wish I would have addressed this issue before I bolted the seat all back in!
Thanks
Chad

[jjzepplin]

Yep just one tan wire going to the sender. Measure Ohms at the sender. 0-90 ohms relative to how much gas is in the tank. You simply could have a bad ground. In my case I had a bad gauge and a bad sender. Find a guy an here named Tbone. He will most likely help you. I cannot find the thread he helped me on. I must have hijacked someone else.

[cjoenny89]

ok thanks! We painted the inside of the cab maybe I am not getting the tank grounded?

[jjzepplin]

Has it worked correctly in the past?

[VetteVet]

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

[cjoenny89]

thanks everyone I will do they test and see what I find out! thanks!

[cjoenny89]

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Ok I pulled the brown wire of fuse block and turned key on and gauge went from 1/4 full to like 4 or 5 o'clock position way past full. plugged it back up and turned key on it went to empty.
I ohmed out the wire un-hooked from the fuse block to the tank connection to see if the wire was good and it was good but it also shows good when you touch the tank and not both end of the wires. could my problem be a pinch wire onto the frame or will I get this from one end of the wire to the other or to the tank it showed closed not open. It just acts like one big ground?
I thought I should have have showed open from the touching the tank to the end by the fuse block and only close from each end of the wire is this where my problem is coming from?
I even ran a ground from the batter to the tank and then tried it gauge still went to zero.
I am guessing I have my fuel sending wire pinched and is grounded out? or my sending unit is bad?
Thanks for the help!
Chad

[jjzepplin]

What was the ohm reading from the sender? Measure that then if acceptable(0-90) then reconnect wire and check for the same reading at the fuse block end of the wire. If you are unsure of the wire run a new one temporarily.
The link above will tell you how to test the gauge to make sure your not chasing your tail.

[cjoenny89]

Pulled brown wire off both ends it is good it is closed in ohm test. I get 15.9 ohms on sender unit no wire hooked up. Wire hooked up I got like 16.8 ohms I think at brown wire on fuse block end. I pulled resistor on fuel gauge and it ohmed out at 90.5 ohms. I put it back on. After doing all this it shows 3/8 tank until you turn key on the it is empty. It was at 1/4 tank before i started all this. I will put some gas in it and see if the ohms go up just need to figure out why it goes empty when key is on.

[FirstOwner69]

My bet is that the sending unit float is filled with gas. Here's a link to the float I used when my gauge behaved in a similar fashion. I got mine on eBay for about $6.00. My leaker was on a new sending unit. The new float snapped right in.
http://67-72chevytrucks.com/vboard/s...d.php?t=666161

[mike16]

my sending unit like my gass tank was completely rusted to the point where ther was no internal guts. havent fixed it yet but soon to get a new sender and tank.

[cjoenny89]

New float coming so we I pull it apart and if it needs it I have it