3 Series E46 325i (M56) TOUR
1. Fuel tank (plastic)
15. Expansion tank
2. Electric fuel delivery pump
16. Flood valve
3. Pressure relief valve
17. Rollover valve
4. Non-return flap
18. Pressure regulator
5. Filler neck
19. Fuel filter
6. Tank expansion line
20. Fuel rail
7. Suction jet pump
21. Fuel evaporation control valve
8. Overflow protection valve
22. Engine control unit
9. Fuel filler cap
23. Intake manifold
10. Fuel feed line
24. Flush line
11. Fuel return line
25. Activated carbon filter
12. Refuelling vent line
26. Breather pipe
13. Operating vent line
27. Tank leak diagnosis module
14. Pressure check line (USA only)
28. Dust filter
4.2 Functional description (please refer to drawing 4.4)
Fuel system
The saddle-shaped fuel tank is equipped with an electric fuel delivery pump in the smaller, right-hand side.
The suction jet pump in the left-hand side of the fuel tank transfers fuel via the tank expansion line to the right-hand
side of the fuel tank.
The suction jet pump is driven by the fuel return line.
The pressure relief valve controls the pressure required for the suction jet pump to operate. The overflow protection
valve protects the fuel return line. Should the pressure drop in the event of damage or the fuel return line becoming
separated, the valve will close.
This prevents the fuel from overflowing from the fuel tank in extreme vehicle positions (rollover, inclination).
The non-return flap prevents the fuel from sloshing back in the fuel filler neck when the fuel pump nozzle cuts off.
The flood valve on the underside of the expansion tank protects the system against overfilling when refuelling. The
rising fuel level in the refuelling vent line closes the flood valve and so creates an overpressure in the fuel tank, which
prevents the tank from being filled any further.
Fuel supply to the engine
For description, please refer to "Fuel supply system E38/39,
1.2 Functional description, fuel supply system for engine M54/62".
Ventilation system USA
When refuelling, the fuel tank is ventilated through the refuelling vent line.
Due to its large cross-sectional area, the refuelling vent line quickly feeds the displayed volume (fuel vapours) via the
expansion tank to the activated carbon filter.
The activated carbon absorbs the fuel contained in the fuel vapours. The purified air is then fed into the atmosphere
through the breather pipe, the tank leak diagnosis module and dust filter.
Ventilation during operation of the vehicle is maintained in the same manner through the refuelling vent line and
operating vent lines.
The condensed components of the fuel vapours are fed back from the expansion tank into the fuel tank through the
vent lines.
The rollover valve on the top of the expansion tank will close in the event of the vehicle turning over. This prevents
fuel from draining out into the activated carbon filter.
The activated carbon filter is regenerated by flushing out with fresh air.
SBT Functional description of fuel supply system E38 E39 E46 E52 E53
BMW AG - TIS
15.02.2013 03:46
Issue status (12/2007) Valid only until next DVD is issued
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