Fuel Supply System

16 00 - Fuel supply system E60/E63/E64

1. General
General function description of fuel system Description and Operation.
2. Component designation






3. Function description (see also drawing)
Fuel system
The saddle-shaped fuel tank contains the surge chamber with electric fuel pump on its right side.
The surge chamber ensures that the fuel pump is properly supplied in all vehicle operating states.
The suction jet pumps direct the fuel from the left and right halves of the tank into the surge chamber.
Suction jet pumps utilize the venturi effect to draw in further fuel via a jet and pump on both quantities of fuel.
Return line, pressure regulator and fuel filter are located in the tank.
Fuel supply to engine:
The electric fuel pump draws in fuel from the surge chamber and pumps it to the fuel filter/pressure regulator via the delivery line to the fuel rail.
Pressure regulator and fuel filter are incorporated in a single unit in the tank. This removes the need for a fuel return line.
The pressure regulator limits the pressure in the fuel feed line to 3.5 bar. If the pressure rises above 3.5 bar, the regulator opens a discharge hole. The excess fuel flows back through the discharge hole into the right tank half (surge chamber) and drives the two suction jet pumps.
The fuel rail thus operates on a return-free basis.
Tank venting system (US version):
During refueling, the fuel tank is vented via the filler vent valve and the filler vent line. The gasoline gases are directed during refueling via the filler vent valve and the vent line through the carbon canister and thus discharged in filtered state to atmosphere. The carbon canister of the US version therefore has a larger volume than that of the other national versions.
The filler vent valve in the tank is closed by the rising fuel in the event of overfilling. A pressure cushion is created in the tank when the vent outlet is closed. This pressure cushion creates a backdraft of fuel in the fuel filler pipe. The backdraft of fuel reaches the gasoline pump nozzle and cuts it out automatically. A compensating volume of approx. 6 liters is thus maintained above the fuel level.
The compensating volume incorporates 2 service vent valves.
Both valves are designed as rollover valves. This prevents fuel from escaping from the fuel tank in extreme vehicle positions (overturning, inclined position).
- Reduction of excess pressure:

The process of heating fuel creates excess pressure. The gases rising from the tank flow through the service vent valves and the vent lines to the carbon canister.

- Equalization of vacuum pressure:

The process of pumping off fuel creates vacuum pressure. Air is routed in reverse sequence for pressure equalization purposes. The fuel tank is supplied with fresh air via the air filter (insect strainer) on the carbon canister and via the carbon canister itself.

The carbon canister removes hydrocarbons (HCs) from the gases created in the fuel tank and discharges the cleaned air to atmosphere.
The condensed constituents of the fuel vapors remain in the tank because the tank has an integrated compensating volume.
The carbon canister is regenerated by purging with fresh air.
The DME control unit opens the tank vent valve (depending on the load conditions and on lambda closed-loop control). Thus the vacuum pressure of the engine intake manifold is applied at the purge air line. The carbon canister is purged in this way. The fresh air needed for this purpose is supplied via the tank leak diagnosis module and the dust filter. The fuel constituents bound by the activated carbon are flushed out by the supplied air and directed via the purge line to the engine for combustion.
This operation is only possible while the engine is running.
Tank venting system (worldwide):
Refer to Tank venting system (US version) with following differences:
1. Carbon canister has a smaller capacity.

2. No tank leak diagnosis module or dust filter.

3. No pressure test line.

Leak diagnosis for tank venting system (US version):
The tank leak diagnosis module (see drawing 5.2) serves to diagnose leakages for the tank venting system within the on-board diagnosis laid down by legislation.
The tank venting system is pressurized and the pressure loss is detected in the event of a leak.
The tank leak diagnosis module is activated by the DME control unit and detects the pressure loss by way of the power consumption of the integrated pump. The air required for this purpose is supplied via the dust filter.
Determining fill level in fuel tank:
The fuel fill level is measured by a lever-type sensor on either side of the fuel tank. The fuel level sensor is supplied with 5 V by the instrument cluster and measures the voltage drop via the resistor on which the lever sliding contact rests.
The combination of the determined values from the right and left lever-type sensors produces the actual level in the fuel tank.
4. Service data, fuel system
Operating pressure: 3.5 bar
5. Schematic drawings of fuel supply systems





5.1 Fuel supply system E60/63/64 ECE/Japan





5.2 Fuel supply system E60/E63/E64 US version