Originally Posted by 215ranger
My Q is there has to a vacuum inside the gas tank or not or is it pressure i know that my dads F150 and my cousin mustang makes a sound of the air going in or out when you go get gas because my ranger does not
When the engine is running, the tank can have positive pressure or vacuum or be at atmospheric. When the engine is off, it is more likely to have positive pressure caused by the vapor pressure of the fuel.
I don't know what criteria the inspector was using. Maybe he found a tank leak code stored in the PCM memory.