Patent ID: 6789523
Filing Date: 2004-09-14
Classification: F02D,F02M

Abstract:
A failure diagnosis apparatus for diagnosing a failure in an evaporative fuel processing system having a fuel tank, a canister containing an adsorbent for adsorbing evaporative fuel generated in said fuel tank, an air passage connected to said canister and communicating with the atmosphere, a first passage for connecting said canister and said fuel tank, a second passage for connecting said canister and an intake system of an internal combustion engine, a vent shut valve for opening and closing said air passage, and a purge control valve provided in said second passage, said failure diagnosis apparatus comprising:pressure detecting means for detecting a pressure in said evaporative fuel processing system; engine stoppage detecting means for detecting stoppage of said engine; determining means for closing said purge control valve and said vent shut valve when stoppage of said engine is detected by said engine stoppage detecting means, and determining whether there is a leak in said evaporative fuel processing system according to the pressure detected by said pressure detecting means during a predetermined determination time period after closing said purge control valve and said vent shut valve; gas layer temperature detecting means for detecting a gas layer temperature in said fuel tank; ambient temperature detecting means for detecting an ambient temperature; and inhibiting means for inhibiting the determination by said determining means when a difference between the gas layer temperature and the ambient temperature detected respectively by said gas layer temperature detecting means and said ambient temperature detecting means upon stoppage of said engine is less than or equal to a predetermined threshold value.