Mk 1 1.6 16v zetec, 1999

Every now and then I get a stron smell of petrol coming from the car, it's not all the time, I get it when I park up, or when am driving.

There does not seem to be any leaks.

And its not coming from petrol cap, as its a new one with new seal.

I changed fuel filter, a few months ago, but I have checked this and there is no petrol leaks.