Fuel supply, function - GF07.10-P-1003MI
ENGINE 272.9 (except 272.982) in MODEL 204.0/2 as of model year 2009
ENGINE 272.9 (except 272.983) in MODEL 212
ENGINE 272.9 (except 272.984) in MODEL 207
ENGINE 272.9 in MODEL 204.9
ENGINE 273.9 in MODEL 207, 212
Function requirements for fuel supply, general points
- Circuit 15 ON (ignition ON)
Fuel supply, general points
Under all operating conditions, the fuel supply supplies filtered fuel to the injection valves (Y62) from the fuel tank, in sufficient quantity and at sufficient pressure (injection pressure).
Function sequence for fuel supply
The function sequence for fuel supply is described in the following steps:
- Function sequence for fuel pump control
- Fuel delivery function sequence
- Function sequence for safety fuel shutoff
Function sequence for fuel pump control
The fuel supply is controlled and monitored by the ME-SFI [ME] control unit (N3/10) and the fuel system control unit (N118).
The fuel pump (M3), is switched on when the "fuel pump ON" direct ground signal is received by the fuel system control unit from the ME-SFI [ME] control unit. This signal is sent redundant from the ME-SFI [ME] control unit as a CAN signal via the drive train CAN (CAN C) and as a ground signal.
The fuel system control unit also receives the CAN signal "specified pressure of the fuel" from the ME-SFI [ME] control unit.
The fuel system control unit detects the current fuel pressure by means of a voltage signal from the fuel pressure sensor (B4/7) and transmits this information via the drive train CAN to the ME-SFI [ME] control unit.
The fuel system control unit evaluates the current fuel pressure, compares it with the nominal pressure of the fuel and actuates the fuel pump appropriately by means of a pulse width modulated signal (PWM signal) an.
The fuel system control unit actuates the fuel pump as required so that the actual value of the fuel pressure matches the specified value. The fuel delivery volume is regulated variably from 0 to 130 l/h for a fuel pressure of about 3.8 bar according to the fuel requirements.
Fuel delivery function sequence
The fuel pump suctions the fuel out of the fuel feed module and pumps it through the fuel filter to the fuel manifold (single line system without return line). In doing so, the fuel pressure is limited by the pressure limiting valve to approx. 3.8 bar.
There is a check valve at the feed point of the fuel filter which prevents reduction of the fuel pressure when the fuel pump is switched off.
The fuel return from the pressure limiting valve drives the suction jet pump on the left with fuel. This suction jet pump delivers fuel from the LH fuel tank chamber to the fuel feed module located in the RH fuel tank chamber.
The right suction jet pump is driven by the suctioned off fuel from the fuel pump and also fills the fuel feed module with fuel from the right fuel tank chamber.
Hydraulic scheme shown on engine 272
Function sequence for safety fuel shutoff
The safety fuel shutoff system is designed to ensure traffic and passenger safety.
The ME-SFI [ME] control unit controls the safety fuel shutoff on the basis of the following sensors and signals:
- crankshaft Hall sensor (B70), engine speed
- throttle valve actuator (M16/6), throttle valve position
- supplemental restraint system control unit (N2/10) (model 204), Supplemental Restraint System control unit (N2/10) (model 207, 212), direct crash signal
- supplemental restraint system control unit (model 204), supplemental restraint system control unit (for model (model 207, 212), indirect crash signal via the chassis CAN (CAN E)
The safety fuel shutoff is activated by the ME-SFI [ME] control unit under the following conditions:
- Mechanical fault in the throttle valve actuator
- Absence of the engine speed signal
- Crash signal
Mechanical fault in the throttle valve actuator
When evaluating the throttle valve position, if the ME-SFI [ME] control unit detects a mechanical fault in the throttle valve actuator, engine speed is limited to about 1400 rpm at idle and about 1800 rpm in driving mode by shutting off the fuel injection valves.
Absence of the engine speed signal
If the engine speed signal generated by the ME-SFI [ME] control unit is missing, the fuel pump is shut off via the fuel system control unit.
Crash signal
If the ME-SFI [ME] control unit receives a crash signal indirectly via the chassis CAN or directly from the supplemental restraint system control unit (for model 204), supplemental restraint system control unit (for model 207, 212), it switches off the fuel pump via the fuel system control unit (directly and via the drive train CAN) and briefly actuates the fuel injectors in order to depressurize the fuel system.
| Electrical function schematic for fuel supply | MODEL 204 | PE07.10-P-2703-97FAB | |
| MODEL 207 | PE07.10-P-2703-97EAB | ||
| MODEL 212 | PE07.10-P-2703-97DAB | ||
| Electrical function schematic for safety fuel shutoff | MODEL 204 | PE07.10-P-2733-97FAB | |
| MODEL 207 | PE07.10-P-2733-97EAB | ||
| MODEL 212 | PE07.10-P-2733-97DAB | ||
| Overview of system components motor electronics (ME-SFI) fuel injection and ignition system | GF07.61-P-9997MI |