Evaporative Emissions System: Description and Operation

Evaporative Emission (EVAP) Control System

Refer to the System Diagram to see the functional layout of the system.

EVAP Canister
The EVAP canister temporarily stores fuel vapor from the fuel tank until it can be purged back into the engine and burned (Refer to the System Diagram to see the functional layout of the system).

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




Fuel Tank Pressure (FTP) Sensor
The FTP sensor converts fuel tank absolute pressure into an electrical input to the PCM.




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

- The EVAP 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 canister purge 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 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 canister.