What is a canister purge valve, and how does it function?

The canister purge valve is a vital part of the Evaporative Emission Control System (EVAP). The EVAP system seals the fuel system of your vehicle to prevent harmful fuel vapors from entering the environment. In particular, the canister purge valve is an emissions control component that allows the engine intake vacuum to take the exact amount of fuel vapors from the EVA canister into the engine intake manifold.

In newer model vehicles the purge valve is electrically operated solenoid controlled by the engine computer. When your engine is off the valve is closed. Once your engine is up and running the computer continuously and moderately opens the purge valve. This action allows fuel vapor to move from the charcoal canister to burn in the engine. A hose connects all of these parts to form the EVAP system. Like many automotive parts, dust and dirt can clog the canister. The purge valve can even crack from harsh conditions in the environment. If the purge valve fails, it can cause problems for the EVAP system which will negatively affect your car’s emission output level.