| Active charcoal filter system |
| Depending upon the air pressure and ambient temperature, fuel vapour will form above the level of fuel in the tank. |
| The active charcoal filter system prevents these HC emissions escaping to the atmosphere. |
| In limited quantities, fuel vapours pass through a gravity valve (which closes at an angle of 45°) located at the highest point in the tank and through a pressure retention valve into the active charcoal filter. |
| The active charcoal stores these vapours like a sponge. |
| When the car is being driven and the lambda control is active (engine warm), the active charcoal filter solenoid valve 1 -N80-, also known as regeneration valve, is activated (pulsed) by the engine control unit depending upon load and engine speed. The opening period depends on the input signals. |
| Intake manifold vacuum draws fresh air through the breather opening during the purging procedure (active charcoal regeneration). The fuel vapours stored in the active charcoal and fresh air are fed to combustion in metered quantities. |
| The breather valve prevents fuel vapours from being drawn from the fuel tank when the active charcoal filter system solenoid valve 1 -N80- is open and intake manifold vacuum is present. It thus ensures that the purging of the active charcoal filter has priority. |
| When not energised (e.g. open circuit), the solenoid valve is closed. The active charcoal filter will not be purged. |
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| Hose connections are secured with either spring-type or clamp-type clips. |
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| Always replace clamp-type clips with spring-type clips. |
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| Spring-type clip pliers -VAS 5024A- are recommended for installation of spring-type clips. |
| Assembly overview - parts of active charcoal filter system → Chapter. |
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