| Functioning of the activated carbon filter system |
| Depending upon the air pressure and ambient temperature, fuel vapour will form above the level of fuel in the tank. |
| The active carbon filter system prevents these HC emissions escaping to the atmosphere. |
| Fuel vapours pass through a gravity valve located at the highest point in the tank and through a pressure retention valve into the activated carbon filter in limited quantities. |
| The active carbon absorbs these vapours like a sponge |
| When the car is being driven and the lambda control is active (engine warm), the activated carbon 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 is dependent on the input signals |
| During the purging procedure (regeneration of activated carbon) clean air is absorbed through the vent due to the depression of the intake manifold. The fuel vapours stored in the activated carbon and fresh air are fed to combustion in metered quantities. |
| The pressure retention valve prevents fuel vapours from being drawn from the tank when the solenoid valve 1 of the activated carbon filter -N80- is open and there is a depression in the intake manifold. It therefore ensures that the evacuation of the active carbon filter has priority. |
| If there is no current supply (cable open circuit), the solenoid valve is closed. The active carbon 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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| To fit the spring clips, use the spring clip pliers -VAS 5024A-. |
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