why is gas leaking and the tank is not full threw the over flow valve at bottom of tank?

Question

theres no gas around the cap i tried to stop the line up with a screw and a clamp at the bottom. the gas work its way back up to the top of the tank

Answer 1

the gas may be leaking at the over flow valve because of corrosion around the o-ring seal, try looking at the manual that came with the car, it should have some troubleshooting options if you have done these and still leaks, call the dealership and if they ask for you to come in with an estimate see how much it will be and go to different dealerships, after market car repair shops often make slight errors resulting in the outcome that you go BACK to them thus making them have more business, so just ask the dealership

Answer 2

What do you mean "the gas work its way back up to the top of the tank"?
Do you mean with the overflow tube clamped shut, fuel is pooling around the gas cap?
Like was said before, the gas cap seal might be leaking.
With the overflow tube blocked, the fuel would just sit around the top of the gas tank near the cap.