I had the same trouble with cheap overseas sending units. Purchased a unit (non-asian) from mopar mall and had no problems. Installed in original tank.
https://www.moparmall.com/2584947-fuel-trank-gauge-sender-sending-unit-p/303-013.htm
They normally offer 15/20% off during holidays.
This problem is normally ground related if your charging system is working. You should see a ground wire coming from the right side headlight harness and secured on the radiator support. Make sure there's no corrosion on the connector or run a jumper wire from there to the negative side of the...