EVAPORATIVE EMISSIONS SYSTEM VAPOR BLOCKING VALVE LEAK DIAGNOSTIC WITH SINGE PRESSURE SENSOR

A method is disclosed of testing operability of a vapor blocking valve (VBV) in a first passageway that is fluidly arranged between a fuel tank and a carbon canister. A canister valve solenoid (CVS) is arranged in a second fluid passageway that fluidly interconnects the carbon canister and an atmospheric port. The method includes obtaining a first desired pressure in the first passageway, closing the VBV, opening the CVS, monitoring a first test pressure in the first passageway with a pressure sensor, obtaining a second desired pressure in the first passageway, opening the VBV, opening the CVS, monitoring a second test pressure in the first passageway with the pressure sensor, comparing the first and second test pressures, and determining the VBV operability based upon the comparing step.