Evaporative Emissions System: Description and Operation

EVAP (Evaporative Emission) Control System
The EVAP controls minimize the amount of fuel vapor escaping to the atmosphere. Vapor from the fuel tank is temporarily stored in the EVAP control canister until it can be purged from the canister into the engine and burned.

- The EVAP control canister is purged by drawing fresh air through it and into a port on the throttle body. The purging vacuum is controlled by the EVAP purge control solenoid valve, which is open whenever engine coolant temperature is above 147 °F (64 °C).
- When vapor pressure in the fuel tank is higher than the set value of the EVAP two way valve, the valve opens and regulates the flow of fuel vapor to the EVAP control canister.
- During refueling, the fuel tank vapor control valve opens with the pressure in the fuel tank, and feeds the fuel vapor to the EVAP control canister.

Evaporative Emission Control System
Refer to the System Diagram to see the functional layout of the system.

Evaporative Emission (EVAP) Canister
The EVAP canister temporarily stores fuel vapor from the fuel tank until it can be purged back into the engine and burned.

EVAP Canister Purge Valve
When the engine coolant temperature is below 147 °F (64 °C), the ECM/PCM turns off the EVAP canister purge valve which cuts vacuum to the EVAP canister.




Fuel Tank Pressure Sensor
The fuel tank pressure sensor converts fuel tank absolute pressure into an electrical input to the ECM/PCM.