What is a canister purge valve?

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What is a canister purge valve?
Car canister purge valves measure fuel vapour. (luxury car - model toy car image by alma_sacra from Fotolia.com)

Cars rely on several electrical and mechanical components in order to run properly. Some of these parts ensure that the correct fuel mixtures flow through the car engine. A canister purge valve is one such part.

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A canister purge valve is a solenoid valve controlled by the Power Train Control Module. The Power Train Control Module is a control unit that determines the ignition timing, fuel amounts and other parameters needed to keep the engine running.


The canister purge valve serves as part of the emission control system in a car, and it measures the flow and amount of fuel vapour that is recycled into the combustion process via the charcoal canister, or fuel vapour storage device. Canister purge valves are also used in "leak tests," by allowing a vacuum to be created throughout the fuel storage system when the valve is closed, thus preventing outside air from entering the system.


Factors that can affect the performance of a canister purge valve include unclean valve conditions and valve blockage. Valve blockage is caused when an obstruction becomes lodged in the opening of the valve, causing a backup of the fuel and air mixture.

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