I have a 91' Trans Am 305 TPI. I know they had a recall on the "filler neck" which entails the entire gas tank needs to be replaced. I replaced the gas tank and fuel pump (carter pump) and kept the rest original. When I fill up for gas or even 3/4 full, gas leaks out from the filler neck / filler tube down the side of my car and smells of gas, obviously. Why is this happening? The same problem happened with my old gas tank and now its happening with my new tank. Any Advice would be MOST appreciated.

 

Check the gas cap seal, The vent tube to the carbon canister and the canister itself. Either your gas cap is not sealing or there is pressure being built up in the tank.