68 Charger fuel gauge not working properly help

[Lost Sheep]

I have a 68 Charger and the fuel gauge is not showing 3/4 of a tank like it should. Replaced the sending unit in the tank and wont show over 1/2. Anyone have any ideas why or ideas to make a ground to the tank? Thanks 8n advance.

[b5blue]

Buy a fuel sender ground strap.  Don't get stainless they can't grab onto the tubing well. https://www.ebay.com/itm/Mopar-Fuel-Sending-Unit-Ground-Strap-Cuda-GTX-Charger-RoadRunner-Dart-Duster/230843842227?fits=Year%3A1970%7CModel%3ACharger&hash=item35bf5d7eb3:g:g94AAOSwajVUTaGv

[Kern Dog]

Check this out:

[XH29N0G]

You might also look up information on sending units. The original mechanism, as I understand it, has resistance that changes in a non linear way.  The replacements can change in a linear way.  The gauge is calibrated to work with the non linear windings.  I could be completely wrong, but my fuel tank stopped reading correction with a change in sending unit.  I suspect it has been in and out of the tank when restored because there was a small change, but it still isn't right.  I do not remember if I tried the thing KD suggests.  I replaced it in the mid 1990's with the tank.  Next time I am under there I will check.

[b5blue]

Yea the winding's spacing is constant on new units. Factory adjusted spacing to reflect volume reading something aftermarket has no chops to do.