hey guys so i connected the after market fuel gauge connected it to the fuse running 12v connected the ground then i connected the wire from the tank and it started reading im not sure if its right everytime i turn the key it says i have less gas lets say i turn the key it says i have half a tank turn the key off then turn it back it will read less then half a tank what can be causing this would it be the sending unit? any help would be great thanks guys

FORD IS LIFE OIL N GAS IS MY BLOOD