My wife went to fill my recently purchased wagon up and came back complaining that she only put a couple gallons in because it kept spilling gas. I thought she must have had the nozzle in too far or not far enough. But sure enough, everytime I fill it up (at different stations) 2 seconds after pulling the handle, the automatic shutoff on the pump kicks off and then gas comes gurgling out the top (sometimes forcibly). So the process to fill up requires barely pulling the "trigger" then stopping to allow the neck to catch up. Any ideas on what might be going on here? My thought would be a vent line may be clogged. Thanks for any help!