Evaporative Check Valve: Description and Operation

Some fuel injected 4 cylinder engines, except some turbocharged models, are equipped with a combination pressure relief and rollover valve. This valve provides a path for fuel vapors to travel from the fuel tank to the canister and provides fuel leakage protection when a vehicle rollover occurs. This valve also incorporates a pressure relief mechanism designed to release pressure to the atmosphere when fuel tank pressure exceeds that of the calibrated sealing valve.