the check engine light will come on after refueling, and goes out when gas is below 1/4 tank. The manual says it could be bad gas, the top is to securely on, or low fuel, but why does this keep happening over and over.

Has the gas cap been pressure tested lately? I'll bet its bad.

check engine is mostly emissions. If you have a bad gas cap then it will trip the light.

thanx guys

What year is your truck. If it is OBD I, the EVAP system will not set a code or light because of a leak in the system. The gas cap is part of the EVAP system so if your truck is earlier than 95, the cap will not be your light problem.