Auxiliary heater does not function/intermittently does not function

Fig 1: Identifying Fuel Tank Sensor And Electric Fuel Pump

Courtesy of BMW OF NORTH AMERICA, INC.

Index	Explanation
1	Sensor opening to fuel tank
2	Electric fuel pump

Fig 2: Identifying Fuel Tank Sensor And Electric Fuel Pump

Courtesy of BMW OF NORTH AMERICA, INC.

Index	Explanation
A, B	A: Petrol; B: Diesel
A.1/B.1	Suction jet line
A.2/B.2	Mark on suction jet line at level of surge tank cover

Fig 3: Identifying Fuel Line And Suction Jet Line

Courtesy of BMW OF NORTH AMERICA, INC.

Index	Explanation
1	Fuel line
2	Suction jet line

Illustration 4 

Fig 4: Cutting Suction Jet Line

Courtesy of BMW OF NORTH AMERICA, INC.

Index	Explanation
1	Suction jet line
2	Cut off suction jet line diagonally from mark