| 摘要 |
PROBLEM TO BE SOLVED: To provide a failure diagnosing system for an evaporative purging system capable of quickly and accurately detecting the leakage failure even when high air-flow resistance exists between a canister and a fuel tank. SOLUTION: The negative pressure is introduced from the canister by opening a purge VSV. When the tank internal pressure Pt reaches a target pressure Pt0 (time t1), the purge VSV is closed to terminate the introduction of the negative pressure. In a case when the tank internal pressure Pt becomes excessively negative at that time, or when the tank internal pressure Pt is largely lowered by being affected by canister pressure Pc thereafter, a CCV 26 is opened to introduce the atmospheric air to the canister (time t2). The CCV is closed after a predetermined time (time t3), and then the detection of leakage, that is, a process for monitoring the tendency to increase the tank internal pressure Pt is started over a predetermined period, when the tank internal pressure Pt is a proper value at the point of time when a predetermined interval has passed (time t4).
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