Yes, the tank is vented. It has a vent port on the flange and I think the gas cap is a vented style as well. I swear I could hear the pump whirring in the tank when I keyed the power a few times. I had the door open and was listening pretty close and it sounded like it normally does. The whole tank and pump are brand new. I thought about just jumping the relay to keep the pump permanently on, probably wouldn't be a bad idea to keep something to make that easier. Right now the computer is set up to prime the pump for two seconds when the key is turned on, then it shuts off until it sees an rpm signal while cranking when I can hear the relay click on again.