Synchronize Fuel Injection And Firing Order Function - GF07.10-P-1006MRS

Engine 264.9 in Model 205, 253 

Function requirements, general 

• Engine runs

The ME-SFI [ME] control unit (N3/10) detects the Engine running via the evaluation of the crankshaft Hall sensor signals (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.

Synchronization of fuel injection and firing order, general points 

The ME-SFI [ME] control unit synchronizes the injection sequence and firing order.

The ME-SFI [ME] control unit evaluates the signals of the following sensors for the control of the synchronization:

• Intake camshaft Hall sensor (B6/15)
• Exhaust camshaft Hall sensor (B6/16)
• Crankshaft Hall sensor

The ME-SFI [ME] control unit evaluates the input signals and actuates the following components:

• Ignition system
  • Cylinder 1 ignition coil (T1/1)
  • Cylinder 2 ignition coil (T1/2)
  • Cylinder 3 ignition coil (T1/3)
  • Cylinder 4 ignition coil (T1/4)
• Fuel system
  • Cylinder 1 fuel injector (Y76/1)
  • Cylinder 2 fuel injector (Y76/2)
  • Cylinder 3 fuel injector (Y76/3)
  • Cylinder 4 fuel injector (Y76/4)

Synchronization 

When starting the Engine, the injection sequence is specified to match the firing order. To do this the ignition TDC (Top Dead Center) of cylinder 1 must be recognized.

By the 2nd negative signal edge following the gap in the signal from the crankshaft Hall sensor, the ME-SFI [ME] control unit detects the TDC position of cylinders 1 and 4. If the intake camshaft Hall sensor signal is 0 V (low) at this point in time, ignition TDC of cylinder 1 is regarded as detected.

If the signal of the intake camshaft Hall sensor is missing, the signal of the exhaust camshaft Hall sensor is used as a substitute to detect the ignition TDC of cylinder 1. If no signal whatsoever is available from the intake camshaft Hall sensor and the exhaust camshaft Hall sensor, injection and ignition take place after a 360° crank angle in order to enable emergency Engine start.

Crankshaft angle sensor 

On switching off the Engine, the crankshaft angle sensor starts; this also detects turning back of the Engine just before standstill. During a computer run-on of the ME-SFI [ME] control unit, the determined rest position of the crankshaft is stored in degrees of crank angle and used for the next Engine start. If the crankshaft angle sensor does not lead to any result or the switched-off Engine has been turned, the injection sequence and firing order are synchronized during Engine start.

Engine speed signal 

The Engine speed is derived from the crankshaft Hall sensor signal. When the crankshaft is turning, a voltage signal (AC voltage) is generated in the crankshaft Hall sensor by the teeth on the sensor rotor. Here, each tooth generates a voltage pulse. No voltage is generated at the gap where there are 2 missing teeth. The Engine speed signal is a square wave signal with a constant duty cycle of 6 pulses (i.e. one per 60° crank angle) per Engine revolution and a max. current of approx. 20 mA.

If the crankshaft Hall sensor signal fails, the signals of the intake camshaft Hall sensor or exhaust camshaft Hall sensor are used as a substitute (for the limp-home mode).

	Electrical function schematic, synchronization of the injection and firing order		PE07.10-P-2706-97FBI
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MRS