I have a 1991 5.7 Z-28 with 50,000 miles. Lately after fill up gas pours out of the fuel door and down the side of the car. I have replaced the fuel cap and still have the problem. It happens only occasionally and the dealer is stumped. Any ideas?

George

 

Has the factory heat shield between the gas tank and the pipe & muffler been removed? I know that heat will cause a full tank to leak out the filler neck.

 

ITs either an issue with the purge valve not opening and letting built up vapors out.(overpressurizing)

Or the fuel tank vent valve is not letting fresh air into the tank to displace the gas used and it is sucking itself in.

Or a combo of the two.

Do a search for fuel tank vent valve and you will find a part number.

later
Jeremy