Vapor Vent Control Valve

Attach a short piece of hose to carburetor bowl vapor tube of canister. Blow through hose to determine if air will pass vapor vent valve into canister. If not, valve is defective.
Using a vacuum pump, apply 15 in. Hg to vacuum signal tube in diaphragm assembly cover. If diaphragm does not hold vacuum for at least 20 seconds, diaphragm is leaking and canister must be replaced.
With vacuum still applied, again attempt to blow into the carburetor bowl vapor tube of the canister. If valve is sealing properly, air should pass vapor vent valve into canister. If air does not enter canister past vapor vent valve, valve is not functioning properly and canister must be replaced.