ME-SFI starting, function

P07.61-3319-79

Data flow during start

1 Engine start

2 Fuel pressure request

3 Fuel pump ON

4 Actual fuel pressure

5 Coolant temperature

6 Speed and position of right camshaft

7 Speed and position of crankshaft

8 Starter control

9 Boost air temperature

10 Actuation of fuel injection valves

11 Voltage supply, circuit 87

12 Voltage supply 23 V and 180 V

13 Actuation of ECI ignition module

14 Actuation of throttle valve actuator

15 Signals from actual value potentiometer

16 Signals from pressure sensor

17 Actuation and testing of indicator lamps

N10/1 Front SAM control unit with fuse and relay module

N73 EIS [EZS] control unit

N91 ECI ignition system power pack

N92/1 ECI ignition module, right cylinder bank

N92/2 ECI ignition module, left cylinder bank

N93 Central gateway control unit

N118 Fuel pump control unit

Y62/1... Fuel injector

Y62/12 Cylinder 1 to 12

C Drive train CAN

E Chassis CAN

F Central CAN



The ME-SFI [ME] control unit is the gateway for the drive train CAN and chassis CAN.

A1 Instrument cluster

A1e26 "CHECK ENGINE" indicator lamp 

A1e58 Engine diagnosis indicator lamp

B6/3 Camshaft Hall sensor, right cylinder bank

B11/4 Coolant temperature sensor

B17/8 Charge air temperature sensor

B28/4 Pressure sensor downstream of air filter for left cylinder bank

B28/5 Pressure sensor downstream of air filter for right cylinder bank

B28/6 Pressure sensor upstream of throttle valve actuator

B28/7 Pressure sensor downstream of throttle valve actuator

L5 Crankshaft position sensor

M1 Starter

M3 Fuel pump

M16/6 Throttle valve actuator

N3/10 ME-SFI [ME] control unit

Start quantity control
Additional fuel must be injected during start operation, in line with the coolant temperature, in order to facilitate starting of a cold engine. The increased fuel injection quantity is achieved by extending the injection time.

Battery voltage and voltage supply
The injected fuel quantity is determined by the opening times of the fuel injectors. This opening time is dependent on the battery voltage. The ME control unit extends the injection time to compensate the quantity injected if the battery voltage is low. No further engine start is possible below approx. 7 V.

Post-start enrichment

After the engine is started from cold, enrichment with additional fuel is necessary for a short time. The fuel which precipitates on the cylinder walls, is compensated for by this enrichment, and the engine runs smoothly.

-----------------------------------------------------------------------------------------

Synchronizing of fuel injection and firing order

In order to achieve correct synchronization of the fuel injection and firing order for the respective cylinder, the order is synchronized during the first revolutions of the engine. The ME-SFI control unit requires the signals from the camshaft Hall sensor and crankshaft position sensor for this purpose.

Ignition at engine start

When the engine is started and up to approx. 500 rpm, ignition timing is controlled only on the basis of the signal supplied by the camshaft Hall sensor. Only once the engine speed has reached approx. 600 rpm is a transition made from the fixed ignition timing point to the ignition timing point calculated in line with the momentary operating state.

Starter control

The starter solenoid switch is actuated via circuit 50, relay starter by the engine control unit. The voltage supply to the relay is supplied via circuit 15, relay starter. This voltage supply is fused at the front prefuse box (fuse 9).

-----------------------------------------------------------------------------------------

Parking shift lock

Starting is only possible in the selector lever position P/N and when the service brake is operated. The P/N selector lever position information is sent via the CAN from the transmission control unit. The information "service brake operated" arrives via CAN from the ESP control unit (N47-5).



The drive authorization system inhibits the engine management system. Although the starter rotates, the engine does not start.