When the tank is full or if the vehicle is in an unfavourable position, the expansion tank balances out the volume of fuel which changes due to heat, e.g. when the tank is full. It takes up the fuel which is forced out of a full fuel tank as the result of an increase in volume.
Fuel vapor line before left-hand tank half |
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Fuel vapours are also routed via the expansion tank to the carbon canister. It is ventilated via the tank ventilation valve and relieves the pressure via the tank ventilation line.
Tank ventilation valve |
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To ensure fuel cannot flow out of the fuel tank via the expansion tank and the carbon canister when the vehicle is in an unusual position, a valve is installed in the expansion tank (rollover valve) which blocks the fuel connection when upside down.