Many, Many, Many years ago I bought a new Volkswagon from the Dealer, a Karrman Ghia to be correct.

I started to notice after the first few weeks, that when I removed the gas cap to fill it up, I would hear a hiss of air rush into the tank, but never gave it much thought.

Then one day I'm driving and the engine just shuts down, turns over, but won't start. Tow it to the Dealer, Service guy puts the key in and it starts right up, like new.

They find nothing, so I take it home, and on a long drive a few days later, it dies again. Tow it back, and they find nothing.

When I goto pick it up, I mention to the Service guy about the hiss of air with the Fuel cap, and he laughs and says, okay I got the fix.

A dirty stuck valve on the tank that lets in outside air, to balance any pressure build up.

He told me that it was remote, but possible of a collapsed tank, due to a vacuum build up, and outside air pressure.

Who'd have ever thought this was possible due to a stuck valve...