1997 Ford Escort Fuel Guage/ Sending Unit.

Hello. I have a 1997 Ford Escort, and recently my Fuel Guage has stoped working(Stuck on 1/2). Shortly after i put my Speaker System in... Roughly about two or three weeks later, dunno if that had anything to do with it, but i thought id mention it. I thought it was my Fuel Sending Unit. SO i bought a Brand NEW one off the net, and installed it. My Fuel Guage Still didnt work, So i bought a multi-meter, and tested my old one that i had removed from it, and it was reading the correct ohms. (15-99)ohms. Next i took off my dash, part of it, just the plastic cover so i could get to the fuel guage hand. I placed it on Emtpy, and Turn the ingintion switch over, and it went up to 1/2 a Tank. Turn the car off, Still it stayed at 1/2. I then placed the fuel hand over to FULL and repeated the step, and it went back to 1/2. So Im either leaning to a Bad Guage. or a Bad Ground to to the sending unit. I tryed to test the sending unit, while it was isntalled, by putting the positive on the fuel sending unit wire that was coming from the top of the cap, and putting the ground to the top of the cap. AND it read Nothing... So Any help would be much appreciated. Thank You. Email me @ rx_nightfire@Yahoo.com

p.s. The Tank was completly filled up.

Dash:

Old Fuel Sending Unit