Starting, Function - GF07.10-D-1001TSA

Engine 651 in model 907

Block diagram

Starting function requirements, general points

Circuit 87M ON (Engine management ON)
Engine OFF
Drive authorization system 4 (DAS 4) start enable
Engaged gear range "P" or "N" (with automatic transmission)
Start enable clutch pedal switch, full clutch operation (with manual transmission and with code MJ8 (ECO start/stop function))

Starting, general points

The starter control system in the CDI control unit is responsible for the actuation and shutoff of the starter.

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

Engine oil temperature sensor
Fuel pressure sensor
Crankshaft position sensor
Coolant temperature sensor
Speed sensor, for the engine speed
Fuel injectors
Quantity control valve
Fuel pump with fill level sensor via the fuel pump control unit

The start quantity control in the CDI control unit is used for achieving a specific start quantity when the engine is turned on, regardless of the position of the accelerator pedal module.

Function sequence for start

The function sequence is subdivided into the following steps:

Function sequence for start begin
Function sequence for start end (with automatic transmission)
Function sequence for start end (with manual transmission)

Function sequence for start begin

When the start/stop button is pressed twice, the powertrain control unit receives the signal at circuit 50 from the electronic ignition lock control unit (EZS). The powertrain control unit then sends the signal at circuit 50 to the CDI control unit.

Alternator, status via the drive LIN
Electronic ignition lock control unit (EZS), signal at circuit 50 via suspension FlexRay
Fully integrated transmission control electric controller unit (VGS), with code G42 (7G-TRONIC PLUS), driving stage via powertrain CAN
AdBlue® control unit

The CDI control unit coordinates the injection sequence during starting based on the signals from the crankshaft Hall sensor and from the camshaft Hall sensor.

The CDI control unit actuates the following assembly parts to start the engine:

Starter
Pressure regulator valve

The CDI control unit actuates the circuit 50 starter relay (F152kC) with a ground signal. The power contact of the relay closes and the solenoid switch of the starter is supplied to "circuit 50" with voltage from "circuit 30".

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

No start enable from the AdBlue® control unit occurs if the AdBlue® container is empty and the number of permissible engine starts with an empty AdBlue® container is zero.

Function sequence for start end (with automatic transmission)

Starter control is carried out automatically by the CDI control unit (touch start). This means that once the starting procedure is initiated, the shutdown of circuit 50 no longer has any effect on the starting procedure. When the engine cranking speed of 400 to 700 RPM or a starting time of approx. 5 to 40 s (depending on the coolant temperature) is reached, the CDI control unit interrupts the negative activation to the circuit 50 starter relay and thus ends the starting procedure. The starting procedure can only be aborted by switching off the ignition.

Function sequence for start end (with manual transmission)

When the engine cranking speed of 400 to 700 RPM is reached or when the circuit 50 signal is no longer present, the CDI control unit interrupts the negative activation to the circuit 50 starter relay and thus ends the starting procedure. The starting procedure can also be aborted by switching off the ignition.

The starting procedure is inhibited for approx. 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).

A voltage dip limiter is installed at the positive battery terminal. Its task is to prevent a drop in the battery voltage below a defined voltage value during the starting procedure of the engine. This is performed through temporary limitation of the starter current. Note here that 12 V is present on the starter positive line during the starting procedure.

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