To improve reliability of a failure diagnostic device and a failure diagnostic method of an evaporation system performing leak detection by measuring behavior at a time of negative pressure introduction by a pump.
Negative pressure is introduced by the pump 50 under a condition of selecting a reference passage system 80 including a reference leak hole 85 by a selector valve 70 and first reference pressure measurement is performed by a pressure sensor 90 for leak failure diagnosis of the evaporation system 35. Then, the selection valve 70 is switched, leak measurement of the evaporation system 35 is performed by the pressure sensor 90 under a condition of introducing negative pressure to the evaporation system 35 by the pump 50. If pressure measured by the pressure sensor 90 does not reach a first reference pressure, negative pressure is introduced to a reference leak system 80 again by the pump 50 and second reference pressure measurement is performed. Reliable leak detection of the evaporation system 35 can be done by reflecting a second reference pressure in which condition of the pump 50 is close to that at a time of leak measurement of the evaporation system 35.
Toshio Morita
Takao Matsuyama
Tadashi Muto
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