Apparatus for venting fuel vapors

Apparatus for venting fuel vapors present in the fuel bowl of a carburetor for an internal combustion engine, said carburetor having at least one air passage through which air is drawn into the engine, a throttle valve positioned in said air passage and movable between an open and a closed position to control the flow of air therethrough, a fuel circuit by which fuel is delivered from said fuel bowl to said air passage for mixing with air passing therethrough, and fuel metering rod responsive to the movement of the throttle valve for controlling the quantity of fuel delivered through said fuel circuit, the apparatus comprising:

• a fuel bowl cover having a vent through which fuel vapors discharge when the vent is open;
• a fuel pump comprising a piston movable in a cylinder for supplying fuel from said fuel bowl to said air passage as said throttle valve opens, the fuel pump including a stem connected to the piston, said stem being substantially axially aligned with said vent and having an axial bore therein;
• a valve for opening and closing the vent, said valve comprising a washer mounted on a screw which is received in said axial bore, the position of said screw in said bore being adjustable thereby to seat said washer against said cover and close said vent;
• and,
• means responsive to the movement of said throttle valve for actuating said pump as said throttle valve opens whereby said valve is open and vapors in said fuel bowl are vented, said pump actuating means comprising a shaft adapted for rotational movement by said throttle valve as it opens and closes, an S-link connecting said shaft to said stem to move said stem to a position in which said valve carried thereby seats against said fuel bowl cover when said throttle valve is substantially closed thereby to close said vent and to move said stem and said valve away from said cover as said throttle valve opens thereby to open said vent, the position of said shaft when said throttle valve is at other than its substantially closed position being sufficient to maintain said stem and said valve in a vent opening position whereby said vent is closed only when said throttle valve is substantially closed and is open at all other throttle valve positions.