Patent ID: 6651491
Filing Date: 2003-11-25
Classification: F02M

Abstract:
A failure diagnostic system of an evaporated fuel processing system, comprising:a first failure diagnostic device for shutting off an evaporated fuel purge passage connecting a fuel tank and an engine intake passage from air in a first operating range and determining whether there is any leakage from a large hole by monitoring a degree of increase in pressure in the fuel tank in which intake negative pressure is introduced; and a second failure diagnostic device for reducing a pressure in the fuel tank to a predetermined negative pressure and sealing off the fuel tank from air in a second operating range to carry out failure diagnosis to determine whether there is any leakage from a small hole by monitoring a degree of increase in pressure in the fuel tank; wherein said second operating range substantially includes said first operating range and is extended from said first operating range to include a lower intake negative pressure range.