SEAT Workshop Service and Repair Manuals

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.

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 in limited quantities.

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.

During the purging procedure (regenerating the activated charcoal), the intake manifold vacuum draws fresh air through the vent hose on the activated charcoal filter. The fuel vapours stored in the activated charcoal and fresh air are fed in doses for combustion.

The pressure retention valve prevents fuel vapours from being drawn from the tank when the activated charcoal filter solenoid valve (N80) is open and intake manifold vacuum is present. It thus 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.

Notes:

• ◆ Hose connections are secured with either spring-type or clamp-type clips.
• ◆ Always replace clamp-type clips with spring-type clips.
• ◆ Assembly tool VAS 5024 or hose clip pliers V.A.G 1921 are recommended for fitting spring-type clips.

Observe safety precautions.

Observe rules for cleanliness => Page 20-12.

Check activated charcoal filter system => Page 20-45.

Check fuel tank breather => Page 20-55.