| 摘要 |
<p>PURPOSE:To keep a fuel component flow passage system reaching a purge passage from a fuel tank via a canister in a sealed condition so as to diagnose the existence of leakage on the basis of a change in a pressure before sealing and a pressure after sealing. CONSTITUTION:When an engine enters an operation area in which diagnosis can be carried out, a purge control valve 26 and a drain cut valve 27 are closed, and a fuel component flow passage system 28 is kept in a sealed condition, so that evaporative fuel generated in a fuel tank 21 can escape nowhere. Therefore, a pressure is gradually increased if there is no leakage, while a degree of pressure increase is reduced if leakage occurs. A pressure sensor 29 detects a pressure value before sealing and a pressure value after sealing, and a control unit 34 compares the differential pressure with a reference value and diagnoses the existence of leakage.</p> |
