OK, so it seems like the ground is real important to a correctly working fuel guage.  I've consulted the manual which tells me it works on a resistance methodology.  What I didn't figure out is, how do I make sure there is a good ground?  The sending unit seems to be located on the top of the tank and the wiring diagram only shows one wire going to the unit, implying that either there is a ground wire that isn't shown or that the unit grounds itself to the tank by virtue of its mount and the tank is grounded to the frame (probably by its mounts).  Do I have to drop the tank to get to everything or is there a royal road to fixing the guage via improving the ground?

OK, so it seems like the ground is real important to a correctly working fuel guage.  I've consulted the manual which tells me it works on a resistance methodology.  What I didn't figure out is, how do I make sure there is a good ground?  The sending unit seems to be located on the top of the tank and the wiring diagram only shows one wire going to the unit, implying that either there is a ground wire that isn't shown or that the unit grounds itself to the tank by virtue of its mount and the tank is grounded to the frame (probably by its mounts).  Do I have to drop the tank to get to everything or is there a royal road to fixing the guage via improving the ground?

My guage sender float at the tank has 2 wires coming from it and is grounded behind the left side tail light. This ground is sometimes subject to accelerated corrosion due to the location above and behind the tire. I would suggest checking the harness plug behind the tail light as well as the ground in the same area.

Does your guage work at all?

You could add a ground wire from
the tank to the body, also, check
your body ground between the battery
(small wire) and the body

My gauge never seems to go to full, it might get around 3/4 tank and goes down from there.  I added the ground wire to the factory harness and it didn't change anything on mine, also I couldnt' get the screws loose to take out the sending unit so I am going to have to drop the tank if I decide to change the sending unit....which I dont' know if I am going to bother with.

LOL ok my gage goes almost all the way to the Full mark, but if i stop and fill up the tank when it hits empty it only takes 8.5 gallons,  so i did some research and found out that it is suposed to have a 10 gallon tank, so i took a 2 gallon gass can filled it put it in the back of the kik, and when it got to e i reset the spedometer and drove until it died, 44.5 miles after the gage hits the e mark, put 2 gallons of gass in  drive to the gass station and put  8.2 gallons in the tank

my thoughts is it reads all but 2 gallons of the bottom of the tank and all but 2 gallons of the top of the tank.