I have a question. The last few times I've filled up, when I unscrew the filler cap there is the distinct sound of air entering the tank. My deduction is that it appears that as the petrol is consumed, there is no air replacing it's volume in the tank.

Normally, I would imagine any such liquid tank system requires a 'breather' in order that a vacuum (or at least very low pressure) is not created when the petrol leaves the tank. This does not appear to be happening with me.

It may well be that this is quite normal and I've just never noticed it before. However, that being the case, I'd have to say it is extremely un-Porsche to design a system that way as, naturally, with no breather to equalise the space in the tank the fuel will become progressively harder to draw out (although I guess this will not ever become seriously problematic).

Has anyone an opinion on this? Perhaps there is a breather which has become blocked?

Thanks.

 

I think that the government-mandated rules require what you describe. I've heard that when the vapor lock mechanism fails the ECU throws a warning.

BTW... all my cars do that.