GF07.16-P-0001GZ Common Rail Diesel Injection (CDI), Function

GF07.16-P-0001GZ Common Rail Diesel Injection (CDI), Function
ENGINE 642.940 in MODEL 164.120 /122 /822 up to model year 2008
/YoM 07
ENGINE 642.9 in MODEL 463 up to 31.5.12

Diesel engine OM 642 is characterized by and excels due to the following basic innovations:
^ Common rail diesel injection (CDI) 4
^ V6 crankcase made out of aluminum instead of cast iron
^ Balance shaft located in the "V" of both cylinder banks which
^ turns in an opposite direction to the crankshaft
^ Valve control with roller-type cam follower
^ Load level controlled pre and post injection
^ A flow-dynamics optimized forced induction system consisting
^ of a turbocharger with variable turbine geometry
^ Exhaust gas recirculation (AGR) with water-cooled exhaust
^ gas recirculation cooler
^ Rapid glowing system with glow output stage (N14/3)
^ Highly efficient ventilation system with centrifugal oil
^ separator

The CDI 4 takes account of the following features of the extended demands upon a common-rail injection system:
^ Use of piezo injectors and thus more precise injections
^ Hydraulically optimized 8-hole nozzle module
^ Load-dependent, dual pre-injection to reduce combustion noise
^ Load-dependent, double post-injection in vehicles with code (474) particulate filter
^ Intake controlled high-pressure pump with lower than average
^ operating energy input, leading to reduced fuel consumption
^ A maximum injection pressure of 1600 bar

CDI controls the following functions via the CDI control unit (N3/9):
^ Fuel supply in all operating conditions
^ Controlling the glow functions
^ Injection quantity control
^ Emission control
^ Charge pressure control
^ Shutting of the refrigerant compressor (A9)
^ Shut-off control

To do this, the CDI control unit reads in information from the following sensors:
^ Oil temperature sensor (B1)
^ Left hot film mass air flow sensor (B2/6)
^ Intake air temperature sensor (B2/6b1)
^ Right hot film mass air flow sensor (B2/7)
^ Intake air temperature sensor (B2/7b1)
^ Rail pressure sensor (B4/6)
^ Charge pressure sensor (B5/1)
^ Camshaft Hall sensor (B6/1)
^ Coolant temperature sensor (B11/4)
^ Charge air temperature sensor (B17/8)
^ CAT temperature sensor (B19)
^ Temperature sensor upstream of diesel particulate filter (B19/9), on vehicles with code (474) Particulate filter
^ Pressure sensor downstream of air filter (B28/5)
^ Pressure differential sensor (DPF) (B28/8), on vehicles with code (474) Particulate filter
^ Accelerator pedal sensor (B37)
^ Fuel temperature sensor (B50)
^ Crankshaft Hall sensor (B70)
^ Fuel filter water level sensor (B76) on vehicles with code (494) USA version
^ O2 sensor upstream of CAT (G3/2)
^ Oil level check switch (S43)

The CDI control unit actuates the following actuators:
^ Starter relay (F58kI)
^ Fuel pump relay (F4kO)
^ Throttle valve actuator (M16/6)
^ Intake port shutoff motor (M55)
^ Vent line heater element (R39/1)
^ Left exhaust gas recirculation positioner (Y27/9)
^ Pressure regulator valve (Y74)
^ Cylinder 1 fuel injector (Y76y1)
^ Cylinder 2 fuel injector (Y76y2)
^ Cylinder 3 fuel injector (Y76y3)
^ Cylinder 4 fuel injector (Y76y4)
^ Cylinder 5 fuel injector (Y76y5)
^ Cylinder 6 fuel injector (Y76y6)
^ Boost pressure regulator (Y77/1)
^ Quantity control valve (Y94)

The CDI control unit communicates with the following components via the Local Interconnect Network (LIN):
^ Alternator (G2)
^ Glow time output stage

The CDI control unit is connected to the following control units via the Control Area Network Bus Class C (engine compartment)
^ Instrument cluster (A1)
^ ESP control unit (N47-5)
^ EIS [EZS] control unit (N73)
^ Steering column module (N80)
^ Central gateway control unit (N93)
^ Fully integrated transmission control (VGS) control unit (Y3/8n4)

STAR DIAGNOSIS can be used to read out system errors that occur, which are stored in the fault memory of the CDI control unit. This also applies for system faults which occur in the glow system, which were recognized by the glow time output stage and transmitted via the drive LIN to the CDI control unit.

Fuel supply
The CDI is supplied with fuel by the fuel pump (M3). For this purpose, the CDI control unit actuates the fuel pump through the fuel pump relay, and the pump delivers fuel through the fuel main filter to the common rail high pressure pump. When actuated by the CDI control unit, the quantity control valve regulates the feed to the common rail high pressure pump. Excess fuel flows back into the fuel tank via the return line.

Preheating system control at engine start and when driving
CDI actuates the glow time output stage via the CDI control unit. This in turn actuates the glow plugs (R9). The glow system types are as follows:
^ Preglowing
^ Start-ready glowing
^ Start-glowing
^ Afterglowing
^ Diagnostic glowing

Controlling the quantity of fuel injected at engine start and in normal driving
The CDI controls the fuel injectors (Y76) via the CDI control unit depending on speed and load. A distinction is made between "preinjection", "main injection" and "post-injection".

Emission control system
The emissions from the engine are cleaned in the exhaust system by a near-engine mounted catalytic convertor (CAT). The catalytic convertor is also used to reduce noise pollution. A lambda control is also used. On vehicles with code (474) Particulate filter, a diesel particle filter (DPF) is used.

Boost pressure control
The CDI actuates the boost pressure positioner via the CDI control unit using a pulse width modulation (PWM) signal. The boost turbocharger via a linkage. This controls the boost pressure. Thus a high boost pressure is possible even at low engine speeds.

Refrigerant compressor shutoff
Function requirements:
^ AC system activated
^ Engine speed greater than 2000 rpm
^ The values of the accelerator pedal sensor is less than 95%

The CDI control unit interrupts actuation of the refrigerant compressor. If the above listed function requirements are no longer met, the CDI control unit reactuates the refrigerant compressor.

Shutoff control
The function requirement for shutoff control is "Circuit 15 OFF". Through the CDI control unit, CDI actuates the quantity control valve and the pressure regulator valve. The quantity control valve interrupts the supply to the common rail high pressure pump, and the pressure regulator valve opens the connection to the return line.