94 Aerostar - Beginning this last summer, problems during fueling began. When tankwas full, fuel would spray out of filler pipe as the pump shut off. When I tried a slower fill rate, often the pump would not shut off at all as fuel poured out of the pipe. This has been occurring at several different gas stations. I have been trying to be especially careful, monitoring the fill by sound. Several times, however, as it approaches full, I shut off and pull the nozzle only to have fuel come back up and flow out of the filler (four foot puddle!). I just dropped the tank and inspected the filler pipe, vent, etc. and see nothing out of the ordinary. Any ideas?