Tank Isolation Valve

The fuel tank isolation valve is installed on the carbon canister. The fuel tank isolation valve is activated by the hybrid pressure refuelling electronic control unit (TFE). The fuel tank isolation valve is normally closed when de-energized.

While driving, the pressure is limited to the permissible values by briefly activating the fuel tank isolation valve. The fuel tank isolation valve is also activated in order to relieve the pressure in the pressurized fuel tank before refuelling.

As keeping the valve open would require some power consumption, the activation time is limited depending on the fuel filler flap. The length of activation is 10 minutes if the filler flap is not opened and 15 minutes if the filler flap is opened.

During phases of standstill, the excess pressure and vacuum are limited by two non-return valves that are integrated in the fuel tank isolation valve.

Fig 1: Identifying Tank Isolation Valve

Courtesy of BMW OF NORTH AMERICA, INC.