| Depending upon the air pressure and ambient temperature, fuel vapour will form above the level of fuel in the tank. |
| The activated 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 activated charcoal filter. |
| The activated charcoal stores these vapours like a sponge. |
| When the Lambda control is active when driving (engine warm), the activated charcoal filter solenoid valve -N80-, also called regeneration valve), is activated (pulsed) from engine control unit depending upon load and engine speed. The opening period is dependent on the input signals. |
| Intake manifold vacuum draws fresh air through the vent opening on the underside of the activated charcoal filter during the purging procedure (regenerating the activated charcoal). The fuel vapours stored in the activated charcoal and fresh air are pulse-fed to combustion. |
| The breather valve prevents fuel vapours from being drawn from the tank when the tank venting valve is open and intake manifold vacuum is present. It therefore ensures that the evacuation of the activated charcoal filter has priority. |
| With no voltage (e.g. wiring open circuit), the activated charcoal filter solenoid valve -N80- is closed and the activated charcoal filter will not be purged. |
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| Hose connections are secured with either spring-type or clamptype clips. |
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| Always replace clamp-type clips with spring-type clips. |
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| To mount spring type clips use pliers -T20029-. |
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