Bowl Vent Solenoid: Description and Operation

Fig. 49 Solenoid vent valve:

The purpose of this valve, Fig. 49, is to close off the fuel bowl vent line when the engine is operating. It is a normally open valve located in the fuel bowl vent to canister line. This valve is on carburetors which do not have a built-in fuel bowl vent valve.
When the ignition switch is turned on, the coil energizes and the plunger is pulled against the valve seat to the closed position to prevent purge vacuum from reaching the carburetor fuel bowl and upsetting the balanced air pressure.
When the ignition switch is turned off, the coil de-energizer and spring pressure unseats the plunger to allow fuel vapors to flow to the carbon canister where they are stored until purged when the engine is started. If vacuum from the purge control valve does reach the fuel bowl vent line, the resultant low air pressure in the bowl will cause a lean fuel mixture condition. When diagnosing a driveability problem associated with a lean fuel mixture, check the solenoid vent valve and/or the built-in fuel bowl vent. The vent valves must be closed when the engine is operating.