I have a 2000 XC70 that will not fill up. As soon as I start to pump it shuts off and it takes several minutes to fill the tank...to what I think is full. I have checked the filter at the filler hose and it is clear and unrestricted. There are no other unusual signs at the filler hoses or vent hoses at the tank. Could this be a charcoal canister check valve malfunctioning?