Patent ID: 7040302
Filing Date: 2006-05-09
Classification: F02M

Abstract:
1. A failure diagnosis apparatus for diagnosing a failure of an evaporative fuel processing system which includes a fuel tank, a canister having adsorbent for adsorbing evaporative fuel generated in said fuel tank, an air passage connected to said canister wherein said canister communicates 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; and first 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 for determining whether there is a leak in said evaporative fuel processing system based on a determination parameter corresponding to a second-order derivative value of the pressure detected by said pressure detecting means during a first predetermined determination period after closing of said purge control valve and said vent shut valve.