Evaporative Emissions System: Description and Operation
EVAPORATIVE LOSS CONTROL SYSTEMDESCRIPTION
A canister containing activated charcoal, located in the right hand front wheel arch, is used to store hydrocarbon emissions from the fuel tanks.
Filter pads are fitted above and below the charcoal to prevent ingress of foreign matter into the purge line. Emissions from the fuel tank enter the canister at the bottom, and the purging air enters the canister at the top, passing through the charcoal to the purge outlet also at the bottom.
Canister 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 operated by the delay valves, so that when it is energized (closed), canister purging does not occur for the first 45 seconds after the engine has started.
The pressure relief valve is used to control the transfer vapor from the fuel vapor separator to the charcoal canister. The valve is designed to prevent the flow from tanks until a preset pressure of 0.14 kgf/cm2 (2 lb/in2) is exceeded.