Evaporative Emissions System: Description and Operation

Evaporative Emission Control System:

The evaporative emission controls are designed to minimize the amount of fuel vapor escaping to the atmosphere. The system consists of the following components:

CHARCOAL CANISTER:
A canister for the temporary storage of fuel vapor until it can be purged and cycled through the engine for combustion.

VAPOR PURGE CONTROL SYSTEM:
Canister purging is accomplished by drawing fresh air through the canister and into a port on the throttle body. The purging vacuum is controlled by the purge control diaphragm valve and the purge cut-off solenoid valve.
When the coolant temperature is above 70°C (158°F), the purge cut-off solenoid valve directs manifold vacuum to the purge control valve.
When the coolant temperature is below 70°C (158°F), the purge cut-off solenoid valve blocks manifold vacuum from the purge control valve.

FUEL TANK VAPOR CONTROL SYSTEM:
The fuel cut-off valve and liquid vapor separator prohibit liquid fuel from entering the two-way valve. When fuel vapor pressure in the fuel tank is higher than the set value of the two-way valve, the valve opens and regulates the flow of fuel vapor to the canister. If the two-way valve should fail, the pressure (or vacuum) in the tank is vented through the fuel filler cap.