ME-SFI Starting Function

ME-SFI starting function

ENGINE 104.941 /943 /944 /991 /994as of 1.8.96
ENGINE 104.995
with CODE (494a) USA version
with CODE (807) Model year 1997
with CODE (808) Model year 1998
ENGINE 111.921 /942 as of 1.9.98,
111.943,
111.944 as of 1.8.96,
111.946 as of 1.6.98,
111.947 /973,
111.975 as of 1.8.96
ENGINE 111.945
in MODEL 208.335/435 as of 1.6.98,
202.020 /080 as of 1.9.98
ENGINE 111.974
with CODE (494a) USA version
with CODE (807) Model year 1997
with CODE (808) Model year 1998
ENGINE 112.910 /911 /912 /913 /914 /916 /917 /920 /921 /922 /923 /940 /941 /942 /943 /944 /946 /947 /949 /953 /954 /955 /970 /972 /973 /975
ENGINE 113.940 /941 /942 /943 /948 /960 /961 /963 /965 /966 /967 /968 /969
ENGINE 119.980 /981 /982 /985
ENGINE 120.982/ 983
ENGINE 137.970

Start quantity control
Fuel has to be injected additionally during the start operation, in line with the coolant temperature, in order to facilitate starting of a cold engine. The increased quantity of fuel injected 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 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. The fuel which precipitates on the cylinder walls, is compensated for by this enrichment, and the engine runs smoothly.

Synchronization of 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 position 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.

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

Parking shift lock
On automatic transmission the engine can only be started in selector lever position "P/N" and when the service brake is operated. The information "selector lever P/N" comes via CAN from the AT control unit (N15/3). The information "service brake operated " comes via CAN from ESP control unit (N47-5).

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