I've noticed the last few times I've fueled up that there's no pressure escaping when I undo the gas cap. In the past I've noticed a slight pessure release whenever I've removed the cap. Does this indicate a fault somewhere in the fuel system? Shouldn't there be a constant slight pressure whenever the engine's running, and for a short while, at least, thereafter? What would be the most likely culprit?

I checked the fuel cap rubber seal and it seems soft and pliable still, though I think I'll replace it anyway (is it available separately?).

Thanks

Gary