Patent ID: 6834227
Filing Date: 2004-12-21
Classification: F02M

Abstract:
A fault diagnosis apparatus of a fuel evaporation/dissipation prevention system for collecting an evaporated fuel occurring inside a fuel tank into a canister and introducing the evaporated fuel into an intake passage of an internal combustion engine, comprising:first diagnosis means for serially comparing a first restoring pressure amount measured after a fault diagnosis object region of said fuel evaporation/dissipation prevention system is brought into a reduced pressure state, with a first judgment value and with a second judgment value greater than said first judgment value; second diagnosis means for measuring a second restoring pressure amount by sealing said fault diagnosis object region after an atmospheric pressure is introduced into said fault diagnosis object region when said first restoring pressure amount measured by said first diagnosis mean is greater than said first judgment value or said second judgment value, then comparing said second restoring pressure amount with a third judgment value when said first restoring pressure amount is greater than said first judgment value but is smaller than said second judgment value, and comparing said second restoring pressure amount with a fourth judgment value greater than said third judgment value when said first restoring pressure amount is greater than said second judgment value; and abnormality judgment means for judging said fuel evaporation/dissipation prevention system as being abnormal when said first restoring pressure amount measured by said first diagnosis means is greater than said first judgment value but is smaller than said second judgment value and said second restoring pressure amount measured by said second diagnosis means is smaller than said third judgment value, or when said first restoring pressure amount is greater than said second judgment value and said second restoring pressure amount is smaller than said fourth judgment value.