LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mercedes Benz >> 2013 >> E300 >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Mixture Formation - 212 Chassis - 01 Of 10 >> Basic Knowledge >> Fuel supply, function >> Fuel supply, function - GF07.10-P-1003OG
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Fuel supply, function - GF07.10-P-1003OG

ENGINE 642.8 in MODEL 204 

ENGINE 642.8 in MODEL 207 up to 5/31/13, 212, 218 up to model year 2014 

Function requirements for fuel supply, general points 

Fuel supply, general points 

The fuel supply supplies filtered fuel out of the fuel tank in adequate amounts under all operating conditions at an adequate pressure to the fuel injectors (Y76).

Function sequence for fuel supply 

The function sequence for fuel supply is described in the following steps:

Model 204, model 207.3 as of 12/2009, model 207.4, 212.0 as of 09/2009, model 212.2, model 218 

Function sequence for fuel pump actuation for model 207.3 up to 11/2009 and model 212.0 up to 08/2009 

The CDI control unit (N3/9) actuates the fuel pump (M3) over the fuel pump relay (N10/2kD).

Function sequence for fuel pump actuation for model 204, model 207.3 as of 12/2009, model 207.4, 212.0 as of 09/2009, model 212.2, model 218 

Switching on of the fuel pump takes place when a signal "fuel pump ON" is received by the fuel system control unit (N118). This signal is sent redundantly from the CDI control unit as a CAN signal via the drive train CAN (CAN C) and as a ground signal. The fuel system control unit also receives the CAN signal "Specified fuel pressure" from the CDI control unit.

Function sequence for low-pressure fuel circuit 

The fuel low-pressure circuit consists of the following components:

The FSCU detects the current fuel pressure based on a voltage signal from the fuel pressure sensor (B4/7) (for model 204, model 207.3 as of 12/2009, model 207.4, 212.0 as of 09/2009, model 212.2) or fuel pressure sensor (model 218) and transmits this information via the drive train CAN to the CDI control unit. The fuel system control unit evaluates the current fuel pressure, compares it with the specified fuel pressure and actuates the fuel pump with a pulse width modulated signal (PWM signal) as required such that the actual value corresponds to the specified value.

During actuation the fuel pump suctions the fuel out of the fuel feed module and pumps it through the fuel main filter to the high-pressure pump. Depending on the fuel requirement, the fuel pressure is regulated to about 4.0 bar via the pressure limiting valve integrated in the high-pressure pump.

In addition, the quantity control valve regulates the supply of fuel to the high-pressure pump depending on the engine operating point in order to keep the fuel temperature low.

IMPORTANT The leak fuel and fuel that is not required are fed back to the fuel tank via the return line.

IMPORTANT Fuel preheating system

In order to guarantee the flowability of the fuel at low outside temperatures, engine 642.8 is fitted with a fuel filter condensation sensor with heating element (B76/1) for water level monitoring.

On engines with engine timing CR6+ the heating element is energized by the front SAM control unit with fuse and relay module (N10/1) and heated by the fuel in the fuel filter.

The CDI control unit receives information about the current condensation level from the fuel filter condensation sensor.

On engines with engine timing CR60 the heating element is energized by the glow output stage (N14/3) and heated by the fuel in the fuel filter. The condensation level in the fuel main filter is monitored by means of the fuel filter condensation sensor with heating element. The CDI control unit receives the information on the condensation level via the glow output stage and the drive LIN (LIN C1) by the fuel filter condensation element.

Above a condensation level of ca. 100 ml the CDI control unit sends a message to the instrument cluster via the chassis CAN which is displayed as a warning message in the multifunction display.

View of fuel system 

Fig 1: Fuel System Flow Diagram
G10242071Courtesy of MERCEDES-BENZ USA

Function sequence for high-pressure fuel circuit 

The high-pressure circuit consists of the following components:

Depending on the signal received from the accelerator pedal sensor (B37), the engine speed and the fuel temperature, the high-pressure pump delivers fuel to the left rail and from there simultaneously to the right rail.

The fuel passes from the respective rail via the high pressure lines to the fuel injectors. The fuel injectors spray fuel in a fine atomized form. The CDI control unit calculates the injection quantity selectively for each cylinder based on a characteristics map for the respective operating condition. The injection quantity is dependent upon the fuel pressure in the rail and the actuation duration of fuel injectors.

The fuel pressure in the rail is controlled by the pressure regulating valve and quantity control valve. The effectively applied fuel pressure in the rail is detected by the rail pressure sensor, continuously passed on to the CDI control unit and limited to a maximum of 1600 bar by the pressure regulating valve.

View of the high-pressure fuel circuit 

Fig 2: View Of High-Pressure Fuel Circuit
G10242072Courtesy of MERCEDES-BENZ USA

Function sequence for safety fuel shutoff 

The safety fuel shutoff system is designed to ensure traffic and occupant safety.

The CDI control unit controls the safety fuel shutoff on the basis of the following sensors and signals:

The safety fuel shutoff is activated by the CDI control unit in the following conditions:

Absence of the engine speed signal 

If the engine speed signal generated by the CDI control unit is missing the fuel pump will be switched off.

Crash signal 

If the CDI control unit receives a crash signal indirectly via the chassis CAN or directly from the Supplemental Restraint System control unit (model 204) or the supplemental restraint system control unit (model 207, 212, 218), it switches off the fuel pump, the quantity control valve and the pressure regulating valve and actuates the fuel injectors briefly in order to depressurize the fuel system.

IMPORTANT Fuel pump actuation

Via the fuel pump relay (on model 207.3 up to 11/2009 and on model 212.0 up to 08/2009) or via drive train CAN from the fuel system control unit (for model 204, model 207.3 as of 12/2009, model 207.4, 212.0 as of 09/2009, model 212.2, model 218).

  Electrical function schematic for fuel supply MODEL 204 PE07.10-P-2703-97FAH
  Electrical function schematic for fuel supply MODEL 207 PE07.10-P-2703-97EAF
  Electrical function schematic for fuel supply MODEL 212 PE07.10-P-2703-97DAF
  Electrical function schematic for fuel supply MODEL 218 PE07.10-P-2703-97XAA
  Electrical function schematic for safety fuel shutoff MODEL 204 PE07.10-P-2722-97FAH
  Electrical function schematic for safety fuel shutoff MODEL 207 PE07.10-P-2733-97EAF
  Electrical function schematic for safety fuel shutoff MODEL 212 PE07.10-P-2733-97DAF
  Electrical function schematic for safety fuel shutoff MODEL 218 PE07.10-P-2733-97XAA
  Overview of system components for common rail diesel injection (CDI)   GF07.16-P-9997OG
scientia non olet · About LEMON Manuals