ME-SFI starting function

P07.61-3194-09

Shows model 219

B2/5 Hot film MAF sensor

B6/1 Camshaft Hall sensor

B11/4 Coolant temperature sensor

B28 Pressure sensor (intake manifold)

L5 Crankshaft position sensor

M1 Starter

M3 Fuel pump

M16/6 Throttle valve actuator

T1/1... - Cylinder 1 to 8 ignition coil

T1/8

Y3/8n4 Fully integrated transmission control (VGS) control unit

Y62 Fuel injection valves

CAN Data bus

N3/10 ME-SFI [ME] control unit

N10/1 Driver-side SAM control unit with fuse and relay module

N10/1kL Starter relay

N10/2kA Fuel pump relay

N73 EIS [EZS] control unit

Start quantity control
In order to facilitate starting of the engine when cold, additional fuel must be injected during starting procedure. The increased quantity of fuel injected is achieved by extending the injection time.

The start quantity control is dependent on:

 Start recognition

 Coolant temperature

 Engine speed

 Engine off time

 Altitude (atmospheric pressure).

Battery voltage and voltage supply
The injected fuel quantity is determined by the opening times of the fuel injection valves. This opening time is dependent on the battery voltage. The ME control unit extends the injection time in order to compensate the quantity injected if, for example, 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.

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fuel which precipitates on the cylinder walls, is compensated for by this enrichment, and the engine runs smoothly. The post-start enrichment is dependent on:

 Coolant temperature at start

 Selector lever position

 Combustion cycles after start

 Correction programming with STAR DIAGNOSIS

Synchronizing fuel injection and firing order

In order to achieve correct synchronization of the fuel injection and firing order to the particular 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 Hall sensor for this purpose.

Ignition at engine start

When the engine is started and up to approx. 500 rpm, the ignition timing point is controlled only on the basis of the signals 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.

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Starter control

The solenoid switch of the starter (circuit 50) is actuated through the starter relay by the engine control unit.

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

Parking shift lock

With automatic transmission, the engine can only be started in selector lever position "P/N" and when the service brake is operated. The information on the selector lever position P/N comes via CAN from the transmission control unit. The information "service brake operated " comes via CAN from ESP control unit.

Fuel in the engine oil

For a cold start, fuel may get into the engine oil. When the engine oil is heated, the fuel is reevaporated and is combusted via crankcase ventilation in the engine. The mixture deviation that occurs when the engine is idling can be up to

30%. Lambda control corrects this deviation. Mixture adaptation saves this correction as a long-term effect. A subsequent start could fail if the start mixture is too lean, although no exhalation of fuel takes place. To prevent this, the ME control unit constantly calculates the fuel quantity in the engine oil. To do this, the number of starts, the start temperature and the subsequent operating duration are evaluated.