GF07.10-P-1006MMC Synchronize Fuel Injection and Firing Order Function
GF07.10-P-1006MMC Synchronize Fuel Injection And Firing Order Function
- ENGINES 157.9 in MODEL 216.3, 221.0 /1
- ENGINES 278.9 in MODEL 216.3, 221.0 /1
Function requirements synchronization of fuel injection and firing order, general points
- Circuit 87M ON (engine control ON)
- Engine running
Synchronization of the fuel injection and firing order, general points
Synchronization of the injection and firing order is processed for actuation of ignition coils (T1) and the fuel injectors (Y76) by the ME-SFI [ME] control unit (N3/10).
Furthermore, synchronization is required for the knock control and the fuel shutoff on the individual cylinders.
The ME-SFI [ME] control unit synchronizes the injection and firing using the signals from the following sensors:
- Crankshaft Hall sensor (B70), engine speed and crankshaft position
- LH and RH intake camshaft Hall sensors (B6/4, B6/5), intake camshaft positions
- LH and RH exhaust camshaft Hall sensors (B6/6, B6/7), exhaust camshaft positions
Function sequence for synchronization of the fuel injection and firing order
The function sequence is described in the following steps:
- Function sequence for synchronization
- Function sequence for coasting detection
- Function sequence for the engine speed signal
Function sequence for synchronization
When the engine is started, the injection sequence is determined according to the firing order, using the voltage signals from the crankshaft Hall sensor and the camshaft inlet or exhaust Hall sensor. To do this, ignition TDC (Top Dead Center) must be detected in cylinder 1.
The ME-SFI [ME] control unit detects TDC position of cylinders 1 and 6 on the 2nd negative signal edge following the gap in the signal from the crankshaft Hall sensor. If the signal from an intake camshaft Hall sensor is at 0 V (low) at this time, the ME-SFI [ME] control unit processes it in order to detect ignition TDC in cylinder 1.
If the voltage pulse is missing from a camshaft Hall sensor the voltage pulse will be used as a substitute in a certain sequence by another camshaft Hall sensor for recognition of the ignition TDC of cylinder 1.
If no voltage signal is available from any of the camshaft Hall sensors, injection and ignition take place after a 360° crank angle (crankshaft-Angle) in order to allow an emergency start.
Function sequence for coasting detection
When the engine is shut down, coasting detection takes place, which also evaluates the engine turn back shortly before standstill. During a computer run on by the ME-SFI [ME] control unit, the determined rest position of the crankshaft as a °crank angle is stored and used for the next engine start. If coasting detection does not produce a result, or the engine has been turned while shut down, injection and firing order are synchronized at engine start.
Function sequence for the engine speed signal
Using the signal from the crankshaft Hall sensor, the ME-SFI [ME] control unit generates the short-circuit-proof engine speed signal (for example for cold testing and diagnosis) and sends it via the chassis CAN (CAN E).
A voltage pulse (AC voltage) is generated in the crankshaft Hall sensor by the stays on the increment wheel (perforated plate) for a turning crankshaft. 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 on/ off ratio of 6 pulses per engine revolution (60° C A) and a maximum current of approx. 20 mA.
If the voltage pulse fails from the crankshaft Hall sensor, voltage pulses from the intake camshaft Hall sensors, on the left and right are used instead (for limp-home mode) or used by the exhaust camshaft Hall sensors, on the left and right.
Signal assignment
1 Crankshaft angle piece
2 Cylinder top dead center and firing order
3 Crankshaft Hall sensor voltage pulse
4 Engine speed signal
5 Voltage pulse from the intake Hall sensor on the left and right
6 Voltage pulse from the exhaust Hall sensor on the left and right
a Recognition of ignition TDC of cylinder 1
- Voltage pulse 3: second negative signal edge after the gap
- Voltage pulses 5 and 6: low
- Voltage pulse 4: changes from high to low
