I had a new gas tank line put in. I was leaking gas above the tank from where you place the gas pump in at the gas station. The old line was rusted - so my mechanic replaced it, but now when I get gas at the station, the pump keeps shutting off after about 1 gallon is delivered - it keeps shutting off the gas pump into my gas tank input. The attendant has to stay there and keep pressing the gas trigger to deliver gas -- it just stops after a few seconds. He said it might be air in the tank -- so he tries turing the pump upside down, but still the problem exists. Can you help me?