this has been a nagging problem for a long time. When the tank is about 1/2 full, the guage suddenly drops to just about empty. When there's more than 1/2 tank, everything is just peachy! It's really frustrating.

Has anyone else come across this problem?

 

There is an arm in the tank that when the fuel pushes it up, as in the full situation, it makes a better ground with the tank and the guage reads better. What could be happening is the arm is not getting a good ground in the tank and causing the guage to have the incorrect reading. Also check the ground wire outside the tank.