Patent ID: 6192742
Filing Date: 2001-02-27
Classification: F02M

Abstract:
A leakage diagnosing apparatus for an evaporated gas purge system having a fuel tank with a removable cap, an intake pipe for an engine, a passage which connects the fuel tank to the intake pipe, a canister installed in the passage for adsorbing evaporated gas, and a purge control valve installed in the passage for controlling a purge of said adsorbed evaporated gas from the canister to the intake pipe, said apparatus comprising:leakage diagnosing means for diagnosing existence of leakage in the purge system by detecting at least one of: (a) pressure in a part of the purge system at least including the fuel tank and the canister if said part of the purge system is hermetically sealed with said cap after introducing air therein, and (b) pressure change in said part of the purge system if it is hermetically sealed with said cap after introducing air therein;means for reintroducing air into said part of the purge system when it is tentatively determined that leakage exists during idling of the engine; andmeans for canceling said earlier tentative determination of leakage existence if it is determined that said cap likely was not sealed with the tank during the earlier diagnosis.