The problem is your treating the unit as a bolt in, to just install it in the tank and expecting it to read properly, it ain't going to happen....I install it, look thru the filler port, and using a long rod move the float, and see what arch of travel it has, you may have to remove it several times to "tweak" the rod so that the gauge reads "accurate", to me the upward travel limit is more important,...I'd rather have a gauge read E, and have a few gallons left, rather than read 1/2 full and run out of gas,.....I look to have the gauge read full with the float stopping about 1"-2" from the ceiling of the tank, but you have to physicaly see what the travel is, and compromise for F and E travel, the float should never sit on the tank floor when installed/adjusted, you'll run out of gas long before the float signals E, the gauge should read E with the float a minimum of 1" off the floor, it's best to have a helper read the gauge as you cycle it thru it's swing, it would be nice if a unit was calibrated for your tank, but there are too many tank sizes, and most sending units are for multible applications
