Fuel gauge

I'm trying to figure out if my fuel gauge is bad or if the sending unit is the culprit.

Anybody have any suggestions?

to test the gauge and wiring,,,,,,,,disconnect the wire from the tank,,,,,,,you should have a connector
near the left rear tail light,,,,,with the wire disconnected and the key on, the gauge should read FULL,,,,,touch that wire to ground and the gauge should read EMPTY,,,,,,,,also check the tank ground wire which should be connected near the top of the right rear shock absorber,,,,,,

OK, so if I disconnect the wire and the needle doesn't move, then my problem is the gauge?

And, if the gauge does move, then the issue is the sending unit?

K-Noods68 wrote:OK, so if I disconnect the wire and the needle doesn't move, then my problem is the gauge?

And, if the gauge does move, then the issue is the sending unit?

Most likely!  There is a wire connector (should be tan? 2nd gen color diagram?)coming from the floor below the left side tail light, look there and clean it and ground as Doni said with a test lead and turn the key on and off.  If its the sender, Doni has a great repair for it, he's posted it many times....you cannot buy one new...

What is your gauge doing,,,,,,does it read EMPTY or FULL all the time,,,,,,,,so we try and narrow down where the problem is,,,,,,,,in the tank or outside the tank,,,,,,,,you test the outside stuff by 1st unhooking the wire that goes into the tank,,,,,gauge should jump to FULL when you turn the key on,,,,,then touching that wire to ground should make the gauge read EMPTY,,,,,so its just a test to get us 1 step closer to the problem area, then we go from there,,,,,more tests,,,,,,so you don't end up with 100 guesses on what is wrong,,,,,,see what you find,,,,,,get us some clues and we will solve the mystery.....

My gauge reads empty at all times. I've gotten a few tips on how to test the gauge and the sender. I haven't been able to get out there to test it yet. I do recall seeing a hanging wire under the dash, when I was poking around with my wiper issue. It didn't cross my mind at the time, but now that I think about it, there might be a loose wire, since the lights on the gauge work.

Check the connection to the fuel gauge.  If the wires are loose of not connected, it will read zero.

I had this problem when I put Hella Sunshine back together.. I went through the whole troubleshooting process, then I finally reached under the dash and discovered the connection was loose. i pushed it together, and then it worked well after that! one of those 'duh' moments

That first test is just to simulate the function of the sender. If the gauge worked as described in the test, then the problem would be with the sender...... As an example, the test went as described in my 68 suburban, indicating a sender problem. I pulled the sender out and with the wires connected, moved the arm up and down, demonstrating that the sender itself was operational......I then stuck the float back into the top of the almost full tank to see if would float.....It didn't!.......The end of the wire arm that wraps around the float had rubbed a hole in it (it was a soldered brass float)... Ordered a new float from LMC for under $6 and now it works great!

Some of the tank floats may have been made from plastic or foam that can deteriorate as a result of the new gas formulations and sink....
It's a drag to hafta drop the tank for this stuff (in my burb, a PO had cut an access hole in the floor) If you can demonstrate that the problem is likely elsewhere, you can solve those problems first......You may still successfully demonstrate a bad sender after the other problems are fixed though......

I modified a NOS sender from a 59 Suburban I got on ebay. After spending about a month cleaning and coating the tank and cleaning up around the tank mount I got inpatient and put the sender in without bending (calibrating) the float arm. Now it reads full almost all the time then runs out at about 3/4 tank. Reminds me of the old VW's with a reserve switch. Anyway much better than no sender at all and when I see I'm getting anywhere close to 3/4 I just fill up again. I'm so happy with having a warning that I see no point in making perfect. One of those things to do next time the tank is out. Good luck with your project!!!