Evaporative emission control system with vent valve

摘要

An evaporative emission control system of an internal combustion engine's fuel system including a vent valve. The vent valve provides a mechanism for closing the evaporative emission control system creating a pressure differential between system and atmospheric under various conditions whereby the system can be automatically diagnosed. The vent valve relieves pressure or vacuum in the system that exceeds a threshold necessary to detect the presence of leaks. The vent valve includes a vacuum actuator providing a low restriction flow path for system purges.