Start, Post-Start Phase And Warm-Up Enrichment, Function - GF07.10-P-1007KJ

ENGINE 281.910 in MODEL 453.0/3/4 

Function requirements for starting, the post-start phase and warm-up enrichment, general points 

• Circuit 87 (Engine management ON)
• Engine runs

Start phase, post-start phase and warm-up enrichment, general 

To ensure stable and smooth engine running during a cold start, the ME-SFI [ME] control unit (N3/10) enriches the fuel/air mixture.

Function sequence for start phase, post-start phase and warm-up enrichment 

The function sequence is divided into the following subfunctions:

• Function sequence for starting mixture enrichment 
• Function sequence for post-start enrichment 
• Function sequence for warm-up enrichment 

Function sequence for starting mixture enrichment 

To allow easier starting when the engine is cold, more fuel has to be injected during the starting procedure.

For the starting mixture enrichment, the ME-SFI [ME] control unit computes the injection period based on the following sensors and signals:

• Coolant temperature sensor (B11/4), coolant temperature for a start
• Crankshaft position sensor (L5), engine speed
• Ignition lock (S2), "circuit 50 signal" via FIR fuse and relay module (F2), driver-side SAM control unit (N10/11) and interior CAN (CAN B) to the ME-SFI [ME] control unit
• Engine off time

Through receiving the "circuit 50 signal" from the ignition lock the ME-SFI [ME] control unit extends the injection period of cylinder 1 injection valve (Y62/1) to cylinder 3 injection valve (Y62/3).

Starting mixture enrichment remains active until the engine speed dependent on the particular coolant temperature is exceeded.

The higher the coolant temperature, the shorter the injection period calculated by the ME-SFI [ME] control unit.

No further engine start is possible below an battery voltage of approx. 7 V.

Function sequence for post-start enrichment 

After a cold start the fuel/air mixture is enriched for a short time to ensure that the engine runs smoothly.

Fuel condensing in the cold cylinder barrels is compensated for by the post-start enrichment.

For the post-start enrichment, the ME-SFI [ME] control unit computes the injection period based on the following sensors and signals:

• Coolant temperature sensor, coolant temperature when starting
• Combustion cycles after start
• DKG control unit (N15/13) (for code 429 (twinamic)), selector lever position via drive train CAN (CAN C)

An additional fuel quantity is added to the engine by the ME-SFI [ME] control unit in line with the characteristics map.

To do this the ME-SFI [ME] control unit extends the injection period of cylinder 1 injection valve to cylinder 3 injection valve.

Function sequence for warm-up enrichment 

Following start and post-start enrichment, the fuel/air mixture undergoes further enrichment by means of warm-up enrichment. The warm-up enrichment compensates for fuel which condenses on the still cold cylinder barrel.

For the warm-up enrichment, the ME-SFI [ME] control unit computes the injection period based on the following sensors and signals:

• Intake camshaft Hall sensor (B6/15), intake camshaft setting
• Coolant temperature sensor, coolant temperature when starting
• Intake air temperature sensor (B17)
• Charge air temperature sensor (B17/8)
• Pressure sensor downstream of throttle valve (B28/7), engine load
• Crankshaft position sensor, engine speed

An additional fuel quantity is added to the engine by the ME-SFI [ME] control unit in line with the characteristics map. To do this the ME-SFI [ME] control unit extends the injection period of cylinder 1 injection valve to cylinder 3 injection valve.

The ignition angles of cylinder 1 ignition coil (T1/1) through to cylinder 3 ignition coil (T1/3) are determined in warm-up by its own characteristics map.

In the idle speed range, injection period is mainly dependent on the coolant temperature at engine start.

For partial load, the crucial factor is the engine load.

Once enabled, the lambda control monitors the injection period.

	Electrical function schematic for start phase, post-start phase and warm-up enrichment		PE07.10-P-2707-97BBA
	Overview of system components motor electronics (ME-SFI) fuel injection and ignition system		GF07.61-P-9997KJ