PURPOSE: To prevent unsteadiness of an air fuel ratio when negative pressure is led in, in a device for diagnosing failure of an evaporative purge system formed in such constitution that evaporation fuel (vapor) in an internal combustion engine is discharged (purged) in an intake system so as to be burnt.
CONSTITUTION: The atmosphere leading hole 33d of a canister 33 is communicated with a purge passage 39 through an atmosphere passage 35, a purge passage 40 and a failure detecting purge VSV41. A purge side VSV38 for communicating with a surge tank 26 is communicated with the purge port 33b of the canister 33 through a purge passage 37. When negative pressure is led in, a tank inter- pressure switching valve 34 is opened, a canister atmosphere hole VSV36 is shut out, the purge side VSV38 is shut out, and the failure detecting purge VSV41 is opened. As a result, since vapor in a tank is led in the purge passage 39 through activated carbons 33c in the canister 33, almost of vapor is absorbed by the activated carbons 33c.
ITO TAKAAKI
HIYOUDOU YOSHIHIKO
KIDOKORO TORU
| JPH02130255A | 1990-05-18 |