Fuel Delivery and Air Induction: Description and Operation

GF07.61-P-3004MLK ME Fuel Supply, Function
- refinement package
- as of model year 09

Component Identification:

Function requirements for fuel supply, general points
^ Circuit 15 ON (ignition ON)
^ Circuit 87M ON (engine control ON)

Fuel supply, general points
In all operating conditions, the fuel supply delivers filtered fuel from the fuel tank to the fuel injection valves in sufficient quantity and at sufficient pressure (injection pressure).

Fuel supply, function sequence
The fuel supply function sequence is divided into the following steps:
^ Fuel pump actuation function sequence
^ Fuel delivery function sequence

Fuel pump actuation function sequence
The fuel pump is actuated directly by the ME-SFI control unit (N3/10) through the fuel pump relay (N10/2kA). The ME-SFI control unit actuates the fuel pump relay with a ground signal. In the case of an actuated relay the fuel pump is connected with "circuit 30".
There is no regulation of fuel delivery. This is only dependent on the on-board power supply and is about 130 l/h.

Fuel delivery function sequence
The fuel pump draws the fuel through the fuel strainer from the bottom of the fuel feed module, and pumps it through the fuel filter and fuel pressure regulator to the fuel-distribution rail (single-line system). The fuel pressure is limited by the fuel pressure regulator to about 3.8 bar.

The fuel return from the fuel pressure regulator flows back into the fuel feed module.
In order to fill the feed module with fuel when the fuel level is low, a suction jet pump is installed in addition to the fuel pump. This is supplied with fuel directly from the fuel pump through a separate fuel line.