GF07.16-P-3012P CDI High Pressure Circuit, Function

GF07.16-P-3012P CDI High Pressure Circuit, Function
ENGINE 642 in MODEL 219.3, 209.3, 211.0 /2, 209.4, 211.6
ENGINE 642 in MODEL 461.3
ENGINE 642.9 in MODEL 463.3 up to 31.5.12
ENGINE 642 in MODEL 221.0, 203.0, 164.1, 203.2, 251.0 /1, 164.8, 221.1 up to model year 2008
/YoM 07





Shown on engine OM 642.910

19 High-pressure pump
21 Left rail
22 Right rail
23 High-pressure lines

B4/6 Rail pressure sensor
B50 Fuel temperature sensor
Y74 Pressure control valve
Y76 Fuel injectors
Y94 Quantity control valve

The high-pressure pump delivers fuel depending on the coolant temperature, position of the accelerator pedal, the engine speed and the fuel temperature into the left rail and from there simultaneously into the right rail. The fuel passes from the respective rail via the high pressure lines to the fuel injectors. The fuel injectors spray fuel selectively for each cylinder in a fine atomized form.
The CDI control unit (N3/9) calculates the injection quantity selectively for each cylinder according a performance 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.
The fuel temperature is detected by the fuel temperature sensor and permanently passed on to the CDI control unit.

Regulation except OM 642.920, OM 642.940 and OM 642.950 with code (494) USA version, except OM 642.920 with code (498) Japan version, except OM 642.920 in model 211.024
At a fuel temperature less than 20°C and up to 30 seconds after engine start, the feed to the high-pressure pump is not controlled by the quantity control valve. The heated fuel returns to the tank through the quantity control valve and the return line. For a fuel temperature greater than 90°C the CDI control unit activates t he tank protection function to protect the fuel tank and the high-pressure pump. This function reduces the injection quantity and rail pressure. The rail pressure is controlled in this time by the quantity control valve.

Regulation with OM 642.920, OM 642.940 and OM 642.950 with code (494) USA version, in OM 642.920 with code (498) Japan version, in OM 642.920 in model 211.024
Regulation of the rail pressure takes place according to the 2-regulator concept.

2-regulator concept
^ The 2-regulator concept combines the known standard regulating circuits, that is rail pressure regulation by the pressure regulator valve and rail pressure regulation by the quantity control valve
^ The 2-regulator concept controls and checks regulation on the basis of specified values for the system

Aims:
^ 1-regulator pressure regulation via the quantity control valve or the pressure regulator valve is possible
^ 2-regulator operation with pressure regulation is possible over the pressure regulator valve and throttling of the high-pressure pump over the quantity control valve
^ Changing of regulating mode in running mode is supported
^ The change between rail pressure regulation via the quantity control valve, via the pressure regulator valve and via 2- regulator operation takes place with the smallest possible disturbances to the rail pressure

Rail pressure regulation is subdivided into 3 regulator modes:

Pressure regulator valve regulation
The rail pressure is regulated via the pressure regulator valve during the starting procedure and for fuel heating. The quantity control valve is controlled opened. Pressure regulating valve regulation takes place under the following conditions:
^ Up to 30 s after the engine starts in idle
^ Up to a fuel temperature of 20°C
^ For OM 942.940 and OM 642.950 up to a 500 rpm higher idle speed or for an injection quantity less than 16 mm 3
^ For OM 642.920 up to a 300 rpm higher idle speed or for an injection quantity less than 30 mm3

2-regulator concept regulation
The rail pressure is jointly regulated in idle and in overrun mode by the pressure regulator valve and quantity control valve.

Quantity control valve regulation
The rail pressure is regulated by the quantity control valve under the following conditions:
^ From 30 s after engine start
^ For OM 942.940 and OM 642.950 from a 500 rpm higher idle speed or for an injection quantity greater than 16 mm 3
^ For OM 642.920 from a 300 rpm higher idle speed or for an injection quantity greater than 30 mm3

The pressure regulator valve is controlled closed.
For 2-regulator concept regulation and for quantity control valve regulation the fuel is heated less strongly than for pressure regulator valve regulation.
After switching off the engine, there is a residual pressure of about 50 to 80 bar in the high-pressure control circuit. The high-pressure system may only be opened after completely relieving the pressure on safety grounds.