Need some help please...

I had the typical fluxuating gas gauge and decided to replace the fuel sending unit. I put everything back togther and put4 gallons into the tank. The guage was reading empty, so I did a fill up. The gas guage went to 3/4l and stopped at 20 gallons. I drove around and the needle would not advance to "F" (full).. I disconnedted the 3 pin harness that connects to the sender and fuel pump, and the guage needle went past "F".. I checked the ground wire with my ohm meter in the harness and the tank. They both appear to have a good ground. Is it possible that the fuel sending unit counld be bad, or should I wait until the gas runs out to see if the gauge moves. Also, is the guage supposed to be on "E" when the ignition switch is turned off? (This is how my explorer operates, but the blazer is staying on past full when the ignition switch is either turn on or off.)

 

On my 95 the gage goes down just a tiny bit with the key off but holds.

 

I was searching the threads and some say that if the gauge passes "F", the problem could be a bad ground. The truck runs perfect and I am assuming that the ground wire coming from the harness is making contact to both the sender and fuel pump. Is there way I could add an additional ground wire to the sending unit?

Thanks
Bizzs