Evaporative Emissions System: Description and Operation

GENERAL
Hydrocarbons from the fuel tank ventilation are channeled to a container filled with activated carbon when the engine is stationary. When the car is driven, the fuel vapor is then sucked into the engine by the EVAP canister purge valve opening and combusted.

The EVAP canister purge valve is a boost pressure control valve controlled by the engine control system. By taking into account the working load, etc. of the engine, it opens when the engine is capable of combusting this excess.

The hydrocarbons are channeled from the outlet via a hose to the intake manifold, where they are combusted together with their ordinary fuel/air mixture.

Evaporative Emission Canister
The evaporative canister consists of a container filled with activated carbon whose function is to temporarily store fuel vapor from the tank.

The canister has connections for intake from the tank, and outlet via the EVAP canister purge valve. In addition, there are openings for fresh air. Air is sucked through these openings, via the carbon to be cleaned, into the intake manifold.

To prevent carbon powder from getting into the EVAP canister purge valve and causing it to jam, as of M1990 the evaporative emission canister has a fine filter in the upper part.