Canister Purge Control Valve: Description and Operation
Canister purgingCanister purging is obtained by connecting the purge pipe to a vacuum source and drawing a controlled quantity of air through the charcoal in the canister.
The purge depression is taken from ports in both throttle housings close to and upstream of the throttle butterflies. A restrictor fitted at the point where the purge pipe divides is used to control the maximum purge air flow rate. In order to inhibit canister purging until the catalytic convertors are 'alight' a purge control valve is mounted in the purge line. The purge control valve is operated by the timer/relay such that when it is energized (closed), canister purging does not occur for the first 45 seconds after the engine has started.