Purge valve leak diagnostic systems and methods

摘要

A leak diagnostic system for a vehicle comprises a tank pressure module and a leak diagnostic module. The tank pressure module selectively outputs first and second fuel tank pressures when an engine is shut down and when engine vacuum is greater than a predetermined engine vacuum, respectively. The leak diagnostic module selectively diagnoses a leak in a fuel vapor purge valve based on the second fuel tank pressure when the first fuel tank pressure is less than a first predetermined pressure.