Zac, are these assumptions correct when you did your testing
As others have stated, if some of the tests were performed with the cluster out and tested good, there could be an issue once it is reinstalled.
- The guages cluster is OEM
- The guage cluster is installed into the car
- The wiring is OEM
Red fish brings up an interesting point about filling the tank.
In this post at the end I have a plot.
Product Review: A100 Fuel Sender For 67 Dart
I have verious senders in the tank in my dart. And I plot sender resistance after draining the tank and adding 1 gallon at a time back to the tank. Your sender should have reading similar.
Lastly please post photos of your sender and the manufacturer and part number.
