Evaporative Emissions System: Description and Operation

Fig. 24 Evaporative emission control system.:

Fig. 25 Evaporative emission control system.:

Fig. 26 Evaporative emission control system.:

CIVIC, CIVIC WAGON & CRX

This system, Figs. 24 through 26, consists of a vapor purge control system and fuel tank vapor control system.
When the purge cut-off solenoid valve is open, intake manifold vacuum opens the purge control diaphragm valve in the canister. When the purge cut solenoid valve is ON, the valve is closed and purge cut is performed. Fuel vapors stored in the canister are purged to the throttle body primary bore by the vacuum generated at the purge port.
When fuel vapor pressure in the fuel tank is too high, the two-way valve opens and fuel vapor is collected in the charcoal canister. When the vacuum in the fuel tank is too high, the two-way valve opens and air mixed with fuel vapor is drawn into the fuel tank through the canister.
The fuel filler cap contains valves to relieve excessive pressure or vacuum in the fuel tank, and also seals the fuel filler neck under normal conditions.