My fuel sending unit seems to be grounding itself out

[texfj40]

My voltmeter indicates the center male connector is grounded for some reason. My thought was that the center male connector of the sender was insulated and that one of the screws holding the unit to the tank was to have a ground wire in order to send an accurate reading to the guage. If the center male connector is supposed to be insulated from a ground...how do you dissasemble to correct? 71 fj40. Your kind assistance is appreciated! Thanks

 

[dargreg]

Its suposed to the question is how many ohms are you getting.The unit is like a big variable resister.

 

[texfj40]

I am getting anywhere from 17-120 ohms from the sender, depending upon level of float. Right now 3/4 full about 30 ohms. I alternate 3 fuel guages (two borrowed that are known to work) to check by and all each indicates barely just under 1/4 full...tank 3/4 full. I have the + hot lead on the left guage post (looking from driver side) and the sender on the right post. I think I may have a ground problem?