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Home >> Mercedes Benz >> 2008 >> E300 >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Mixture Formation - Basic Knowledge - 211 Chassis - 1 Of 2 >> Basic Knowledge >> CDI fuel supply, function - GF07.16-P-2006IJ

CDI fuel supply, function - GF07.16-P-2006IJ

ENGINE 647.961 in MODEL 211 

ENGINE 648.960 in MODEL 220 

ENGINE 648.961 in MODEL 211 

Fig 1: CDI Fuel Supply Function Diagram - Model 211 With Engine 648
G04987349

Model 211 with engine 648 

Fig 2: CDI Fuel Supply Function Diagram - Model 220 With Engine 648
G04987350

Model 220 with engine 648 

The fuel supply (fuel low-pressure circuit) provides a sufficient quantity of filtered fuel to the injection system under all operating conditions and at an adequate pressure.

The fuel is held in the fuel tank.

The swirl pot prevents the fuel pump drawing in air when cornering with a low level of fuel in the fuel tank. On model 211 the housing of the fuel feed module serves as the swirl pot.

Fuel feed 

The fuel pump draws the fuel from the swirl pot through the fuel strainer. The fuel pump then pumps the drawn in fuel to the fuel filter.

In the fuel filter, contaminants are removed from the fuel and the fuel is then pumped on to the high-pressure pump.

In the high-pressure pump, the fuel pressure is limited to approx. 4.5 to 6.0 bar by the fuel overflow valve.

Fuel return flow 

The leak fuel from the fuel injectors, the lubricating fuel from the high-pressure pump and the reduced fuel from the pressure regulator valve and the high-pressure pump returns to the fuel tank via the fuel return.

The returned fuel serves:

Fuel pump actuation 

The fuel pump is actuated by the CDI control unit (N3/9) via the fuel pump relay (N10/2kA for model 211 or K40/5kT for model 220).

in case of model 211.026 USA ONLY

The fuel filter water level sensor detects the water content in the fuel filter and transmits a corresponding voltage signal to the CDI control unit. If the water level in the fuel filter has increased then the CDI control unit sends a message over the CAN data bus to the instrument cluster (A1).

Overheating protection for fuel tank 

The fuel temperature sensor detects the temperature of the fuel delivered from the fuel tank in the high-pressure pump flange. The rail pressure is lowered for an excessively high fuel temperature via the quantity control valve in order to protect the fuel tank from overheating from returned fuel.

  High-pressure pump, component description 19 GF07.02-P-3010IC
  Component description for the fuel injectors Y76 GF07.03-P-6120IC 
  Component description for the quantity control valve Y94 GF07.05-P-6010IC 
  Component description for the pressure regulator valve Y74 GF07.05-P-6020IC 
  Component description for the CDI control unit N3/9 GF07.16-P-6000IC
  Component description for the fuel tank 80 in case of model 211 GF47.10-P-2000IC
    80 in case of model 220 GF47.10-P-2000IK
  Component description for the fuel pump M3 GF47.20-P-2000IC
  Component description for the fuel pump relay N10/2kA in case of model 211 GF47.20-P-2010IC
    K40/5kT in case of model 220  
  Fuel filter - Description of components 70 GF47.20-P-2100IC
  Component description for the fuel filter water level sensor B76 in case of model 211 USA ONLY GF47.20-P-2105IC
  Component description for the fuel temperature sensor B50 GF47.50-P-2010IC