Patent ID: 6637416
Filing Date: 2003-10-28
Classification: F02M

Abstract:
A diagnosis apparatus for detecting an abnormal state of an evaporation gas purge system line having a passage connecting between a fuel tank and an intake pipe for an internal combustion engine, a canister disposed in the passage for adsorbing evaporation fuel gas from the fuel tank, a purge control valve for controlling a purge of the evaporation fuel gas from the canister to the intake pipe and an atmosphere change over valve for opening and closing an atmosphere communication hole of the canister, the abnormal state of the evaporation gas purge system line being due to at least one of abnormal causes among a valve closing lock of the purge control valve, a valve opening lock of the atmosphere change over valve and a large amount leakage that the evaporation fuel gas leaks to atmosphere from a portion other than the atmosphere communication hole, comprising:pressure detecting means for detecting a tank internal pressure of the fuel tank; abnormal state detecting means for judging an existence of the abnormal state by detecting a fact that, when the purge control valve is opened to introduce a negative pressure from the intake pipe to the fuel tank via the passage in a state that the atmosphere change over valve is closed, the tank internal pressure detected by the pressure detecting means does not decrease up to a given negative pressure at a time when a given time has lapsed after opening the purge control valve; and abnormal cause determining means for identifying the at least one of abnormal causes based on the tank internal pressure detected by the pressure detecting means when the existence of the abnormal state thereof is judged by the abnormal state detecting means; wherein the abnormal cause determining means has one of two calculation means, one calculation means calculating a change amount of the tank internal pressure during a given period and the other calculation means calculating an integration value of the tank internal pressure during another given period, and comparing means for comparing one of the change amount and the integration value with at least one of threshold values so that the at least one of the abnormal causes is identified.