Starting, Function - GF07.10-P-1001OGF

ENGINE 642.8 in MODEL 166 

as of model year 2016 

ENGINE 642.8 in MODEL 292 

Starting function requirements, general points 

• Circuit 87 (Engine management ON)
• Engine OFF
• Drive authorization system stage 4 start enable (DAS 4)
• Engaged gear range "P" or "N"

Starting, general points 

The starter control system in the CDI control unit (N3/9) is responsible for actuation and shutoff of the starter (M1).

For starting, the CDI control unit reads the following signals:

• Engine oil temperature sensor (B1)
• - high pressure fuel pressure sensor (B4/6)
• Atmospheric pressure sensor (integrated in the CDI control unit) for detecting the atmospheric pressure
• Crankshaft Hall sensor (B70), for the engine speed
• Camshaft Hall sensor (B6/1)
• Coolant temperature sensor (B11/4)
• Alternator (G2), status
• Electronic ignition lock control unit (N73), "circuit 50 signal" via chassis CAN 1 (CAN E1)
• AdBlue® control unit (N118/5) with CODE U77 (BlueTEC (SCR) diesel exhaust treatment), start enable via drive train sensor CAN (CAN I)
• Fully integrated transmission control unit (Y3/8n4), gear range via drive train CAN (CAN C)

The CDI control unit actuates the following components to start the engine:

• Starter
• Pressure regulating valve (Y74)
• Fuel injectors for cylinders 1 to 6 (Y76/1 to Y76/6)
• Quantity control valve (Y94)
• Fuel pump (M3) via the drive train CAN and the FSCU (N118)

Fuel pump actuation

Actuation of the fuel pump takes place both directly and via the drive train CAN by the FSCU ().

The start quantity control in the CDI control unit serves to calculate a specific start quantity at engine start irrespective of the position of the accelerator pedal sensor (B37).

Function sequence for start 

The function sequence is subdivided into the following steps:

• Function sequence for start begin 
• Function sequence for start end 

Function sequence for start begin 

When the transmitter key ignition key (A8/1) is moved to the start position, the CDI control unit receives the "circuit 50 signal" from the electronic ignition lock control unit via chassis CAN 1.

The CDI control unit actuates the circuit 50 starter relay (F58kM) by means of a ground signal. The power contact on the starter relay closes and the starter solenoid switch is supplied at "circuit 50" with voltage from "circuit 30".

If the CDI control unit detects that the engine is running via the crankshaft Hall sensor and the message "circuit 61 ON" and that the starting procedure has ended via the message "circuit 50 OFF", the driver will then be able to influence the injection quantity and thus the engine speed via the accelerator pedal sensor.

In vehicles with code U77 (BLUETEC (SCR) diesel exhaust treatment), no start enable is issued by the AdBlue® control unit if the AdBlue® tank is empty and the number of permissible engine starts with an empty AdBlue® tank is zero.

Function sequence for start end 

Starter control is carried out automatically by the CDI control unit (touch start). This means that once the start process is initiated, switching off "circuit 50" will have no further influence on the start procedure.

When the engine cranking speed has reached 700 to 850 rpm, or after a starting time of 7 to 10 s (depending on coolant temperature), the CDI control unit interrupts the negative activation of the circuit 50 starter relay and thus terminates the starting procedure.

The starting procedure can only be aborted by switching off the ignition. The starting procedure is inhibited for approximately 1.5 to 3 s before it can be repeated. This occurs so that the rotating pinion of the starter is prevented from meshing with the toothing on the engine clutch plate (ring gear protection).

	Electrical function schematic for starting		PE07.10-P-2701-97NBD
	Overview of system components for common rail diesel injection (CDI)		GF07.16-P-9997OGF