GF07.16-P-3000OHL | CDI start quantity control, function | 5.5.08 |
ENGINE 642.9 in MODEL 221.0 as of Model Year 09 /Modification Year 08
ENGINE 642.9 in MODEL 221.1 as of Model Year 09 /Modification Year 08
General function requirements
Circuit 50 ON
Engine speed below crank disconnect speed
Common rail diesel injection (CDI) start quantity control - general
Start quantity control serves to calculate a specific start quantity at engine start quite independently of the position of the accelerator pedal sensor (B37).
The start quantity depends on atmospheric pressure.
The CDI control unit (N3/9) has an internal atmospheric pressure sensor.
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For this purpose, the CDI control unit reads in the following information over the Controller Area Network (data bus/CAN Bus) (CAN):
- The message "DAS 3 Message MS" and the message "Circuit 50 ON", from the EZS control unit (N73)
- Gear selector switch position "P, N or D" from the DIRECT SELECT gear selector switch (S16/13)
The CDI control unit reads in the following sensors directly:
- Coolant temperature sensor (B11/4)
- Crankshaft Hall sensor (B70), for the engine speed
- Rail pressure sensor (B4/6/)
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Function sequence
The CDI control unit uses the input signals to calculate the respective start quantity and actuates the following components directly:
- Pressure regulator valve (Y74)
- Fuel injectors (Y76)
- Quantity control valve (Y94)
If the CDI control unit detects engine running from the crankshaft Hall sensor and the "tml. 61 ON" message, and the end of the engine start process from the "tml. 50 OFF" message, the driver can then control the injection quantity, and therefore the engine speed, through the accelerator pedal sensor.