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:

CHARCOAL CANISTER:
A charcoal-filled canister, located in the right rear corner of the engine compartment, is used 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, located on the carbon cannister, and the purge cut-off solenoid valve, located on the upper center of the firewall. When the coolant temperature is above 167°F (75°C), the purge cut-off solenoid valve directs manifold vacuum to the purge control valve.

FUEL TANK VAPOR CONTROL SYSTEM:
When fuel vapor pressure in the fuel tank is higher than the set value of the two-way valve, located in the top of the fuel tank, 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.