Testing Diaphragm Operated Purge Valve
Attach a short length of hose to PCV inlet orifice of evaporative canister, and attempt to blow through it. Little or no air should pass into the canister. A small amount of air will pass through a constant purge hose. Using a vacuum pump, apply 15 in. Hg to the control vacuum signal port. If diaphragm does not hold vacuum for at least 15 seconds, canister must be replaced. If diaphragm holds vacuum, again try to blow through PCV hose. An increase in airflow should be observed. If not, canister must be replaced.