i take it most cars had non vented caps? what does a vented cap look like?
i thought about using a pcv valve on the vent line going to the canister-when removed, so it only lets pressure out when needed ?
any points or ideas on this? thanks guys

 

Tank has a vent above the rear axle. Check the passenger side (UK) for a hose with a plastic 'mushroom' on the end of it. That is a 2-way vent to control the tank pressure/vacuum.

RBob.

 

hi thanks, yeah i knew that was there but couldnt find any info on it.
i herd it was oneway only ? ive never had pressure in the tank untill i blocked the canister pipe - now i get that woosh when i take the cap out. car drives fine so i am not too bothered aslong as the tanks not guna explode !!! lol

 

Just wait till you get low on gas. From the pressure built up the fuel pump will start howling. A vented cap looks just like a regular cap. The only thing you do is after it is tight turn it back like a half turn to the tank can vent.

 

one thing i have noticed is that one problem - stutering between 2-3k and in bends has stopped ;-) looks like ive fixed my previous post of 9mpg with this as well fingers crossed
thanks for the help and advice