Gas Cap question

You need to figure out if its pressure or vacuum. If its pulling a vacuum you would likely have some issues with it starving for fuel.
I have been stuck numerous times in my car for one reason or another. I remember one time when I still had a clear plastic fuel filter on it and she stalled out on me it acted as if it was out of gas but it wasn't. After removing the gas cap and putting it back on the car fired up and I was able to drive it home.