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Fuel Filler Cap

The fuel filler cap contains a pressure relief valve to ensure that, if there is a problem with fuel tank ventilation, any excess pressure that may form can escape and the fuel tank is not damaged.

If excess pressure forms in the fuel tank, this causes the valve head (1) and with it the entire pressure relief valve (5) to be lifted off the sealed housing (6). The excess pressure can now escape into the atmosphere. The excess pressure spring (2) determines the opening pressure.

The excess pressure spring uses a defined pressure to push the pressure relief valve onto the sealed housing and is supported by the brace (3).

Fig 1: Identifying Fuel Filler Cap Components
G06896053Courtesy of BMW OF NORTH AMERICA, INC.
INDEX EXPLANATION CHART

Index Explanation
1 Valve head
2 Excess spring pressure
3 Brace
4 Bottom section of housing
5 Pressure relief valve
6 Sealed housing