Gas gauge problems

Dana67Dart said
Where are you doing this grounding? If the car is a unibody the "chassis" and "body" should be the same

I was told by napa to test the sender wire by grounding it to frame,should move the gauge to full,then to plug sender back up and use same test wire to ground sending unit to body,if the gauge moved then the grounding strap at tank needed to be removed and all contact points be cleaned and re-installed