Evaporative Emissions System: Description and Operation

SYSTEM OPERATION

The Evaporative Emission system is designed to limit the amount of fuel vapors released into the atmosphere.
The system consists of a sealed fuel tank, carbon canister, hoses and associated valves, fittings, to connect the system together. Vapors are stored in the carbon canister until engine has been started, then at a pre-determined time the vapors are purged into the intake manifold to be burnt.


CANISTER PURGE (CANP) SOLENOID

The amount of vapors drawn from the Carbon Canister into the engine is regulated by the Canister Purge (CANP) Solenoid.

The Electronic Control Assembly (ECA) signals the CANP Solenoid to open the vacuum passage between the Carbon Canister and Intake Plenum when certain conditions for evaporative vapor purge are met. All the necessary engine conditions and driving modes are provided by the inputs sent to the ECA.

Evaporative Emissions Canister:

CARBON CANISTER

The Carbon Canister stores fuel vapors from the fuel tank until the vehicle is operated, at which time, the vapors will be drawn by engine vacuum into the engine for consumption. Purging of the fuel vapors to the engine occurs only when certain engine conditions are met and is regulated by the Canister Purge (CANP) Solenoid as controlled by the ECA.

Vapor Separator:

ROLLOVER/VENT VALVE

The Rollover/Vent Valve releases vacuum or excessive pressure in the fuel tank to atmosphere. In case of vehicle rollover, the valve prevents fuel tank drainage through the evaporative hoses.


VAPOR SEPARATOR

The Vapor Separator prevents liquid fuel from entering the carbon canister, the Vapor Separator is installed between the fuel tank and Rollover/Vent Valve. As fuel tank pressure increases, fuel is forced toward the Vapor Separator and Rollover/Vent Valve. The Vapor Separator allows the liquid fuel to be drained back to the fuel tank, and the vapors to pass.