Functional description

The tank vent valve controls the regeneration of the activated carbon canister by means of scavenging air. Scavenging air drawn through the activated carbon canister is enriched with hydrocarbons (HC) depending on the loading of the activated carbon. The scavenging air is subsequently fed to the engine for combustion.

The creation of hydrocarbons in the fuel tank depends on:

• Fuel temperature and ambient temperature
• Air pressure
• Fill level in the fuel tank
• Time
  Fig 1: Identifying Tank Vent Valve, Engine Connection, Carbon Canister Connection

  Courtesy of BMW OF NORTH AMERICA, INC.

The amount of fuel vapour drawn in by the combustion engine from the activated carbon canister must be adapted to each operating condition of the engine. To achieve this, the tank vent valve is activated by the engine control by means of a pulse-width modulated signal with fixed or variable frequency.