Starting, Function - GF07.10-P-1001MNC
Engine 276.8 in model 172.4
Starting function requirements, general points
- Circuit 87M (Engine management ON)
- Engine OFF
- Drive authorization system stage 4 start enable (DAS 4)
- Engaged gear range "P" or "N" (for automatic transmission)
Starting, general points
The ME-SFI [ME] control unit (N3/10) reads in the data for all attached components as of circuit 15. The data will also be used if it is plausible at this point in time. The following signals are necessary for starting:
- Left and right intake camshaft Hall sensors (B6/4, B6/5), intake camshaft positions for ignition circuit detection
- Left and right exhaust camshaft Hall sensors (B6/6, B6/7), exhaust camshaft positions for ignition circuit detection
- Coolant temperature sensor (B11/4), coolant temperature
- Crankshaft Hall sensor (B70), engine RPM
- Electronic ignition lock control unit (N73), "circuit 50 signal" via chassis CAN 1 (CAN E1)
The ME-SFI [ME] control unit actuates the following assembly parts to start the engine:
- Starter (M1)
- Cylinder 1 to 6 ignition coils (T1/1 to T1/6)
- Fuel injector for cylinder 1 to 6 (Y76/1 to Y76/6)
- The fuel system control unit (N118) directly and via the drive train CAN (CAN C) and thus the fuel pump (M3)
The ME-SFI [ME] control unit coordinates the injection and firing order during starting based on the signals from the crankshaft Hall sensor and the camshaft Hall sensors.
The starter control in the ME-SFI [ME] control unit takes on actuation and cutout of the starter.
Function sequence for start
The starter control is subdivided into the following points:
- Function sequence for start begin
- Function sequence for start end (vehicles with automatic transmission)
- Function sequence for start end (vehicles with manual transmission)
Function sequence for start begin
When the ignition key (transmitter key (A8/1)) is moved to the start position, the ME-SFI [ME] control unit receives via chassis CAN 1 the "circuit 50 signal" from the electronic ignition lock control unit.
The ME-SFI [ME] control unit actuates the circuit 50 starter relay (N10/1kM) with 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".
Function sequence for start end (vehicles with automatic transmission)
Starter control is carried out automatically by the ME-SFI [ME] 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 engine cranking speed has reached 400 to 700 RPM, or after a starting time of 5 to 40 s (dependent on coolant temperature), the ME-SFI [ME] 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.
Function sequence for start end (vehicles with manual transmission)
On reaching an engine cranking speed of 400 to 700 RPM or upon disappearance of the "circuit 50 signal", the ME-SFI [ME] control unit interrupts 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 starter will be decoupled from an engine cranking speed of 400 RPM. The period of automatic start is limited to the prescribed time through reaching this rotational speed threshold or for not reaching it due to a temperature model of the alternator (G2).
| Electrical function schematic for starting | PE07.10-P-2701-97TAH | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNC |