Abstract: A fuel-vapor purge and air-fuel ratio control system controls the amount of fuel vapor to be purged under an engine vacuum into a carburetor of an automotive engine from a charcoal canister and also controls the air-fuel ratio of an air-fuel mixture to be supplied to the carburetor. The fuel vapor is purged form the charcoal canister by applying the engine vacuum to the charcoal canister only when the air-fuel ratio is controlled. The applied engine vacuum may be regulated to control the amount of purged fuel vapor to change in proportion to the amount of air drawn by the engine, or the amount of purged fuel vapor may be increased to an upper limit when the air-fuel ratio is in a normal air-fuel ratio control region, and the amount of purged fuel vapor may be reduced to a lower limit when the air-fuel ratio is outside the normal air-fuel ratio control region.

Abstract: An outer vent control device for use with a carburetor includes a valve housing adapted to be attached to the outer wall of a float chamber in thermally conductive relation, a first control valve disposed in the valve housing and openable when the engine stops its operation, and a second thermosensitive control valve disposed in the valve housing and closable when the temperature of the float chamber drops below a preset temperature. The second thermosensitive control valve includes a thermosensitive unit and a cover attached to a valve housing thereof in covering relation to the thermosensitive unit. The second thermosensitive control valve also has a valve seat member with a valve seat disposed in the valve housing and a valve body movably disposed in the valve housing and seatable on the valve seat. The valve body has an upper conical surface facing an inlet port remotely from the valve seat. The cover has a ventilation hole defined in the bottom thereof at a lowermost position thereon.

Abstract: An evaporative emission control system for an internal combustion engine, in which fuel vapors generated in a fuel reservoir are stored in a fuel vapor storage canister when the engine is stopped so that the fuel vapors may be used when the engine is in operation. A purge control valve is disposed on a discharge port of the canister. The purge control valve is designed so that it is not opened unless a temperature of the engine exceeds a level above a predetermined threshold even when the engine is in operation. When the engine is operated at a low temperature, the stored fuel vapors in the canister are not released for stabilization in the air-fuel ratio of a mixture fed to the engine, and when the engine is operated at a high temperature, the stored fuel vapors are released into the engine to effectively consume the fuel.