GF07.10-P-1003MI Fuel Supply, Function

GF07.10-P-1003MI Fuel Supply, Function

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).

Fuel supply, function sequence
The function sequence for the fuel supply is described in the following points:
^ Fuel pump control function sequence
^ Fuel delivery function sequence
^ Function sequence for safety fuel shutoff

Fuel pump control function sequence
The fuel supply is controlled and monitored by the ME-SFI [ME] control unit (N3/10) and the fuel pump 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 pump control unit also receives the CAN signal "nominal pressure of the fuel" from the ME-SFI [ME] control unit.
The fuel pump 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 pump 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 feed
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.

Component Identification:

Function sequence for safety fuel shutoff
To ensure traffic and passenger safety, safety fuel shutoff is applied. 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 positioner (M16/6), throttle valve position
- Supplemental restraint system control unit (N2/10), direct crash signal
- Supplemental restraint system control unit, indirect crash signal via the chassis CAN (CAN E)

The safety fuel shutoff is activated by the ME-SFI [ME] control unit in 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 pump 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, it switches off the fuel pump via the fuel pump control unit (directly and via the drive train CAN) and briefly actuates the injection valves in order to depressurize the fuel system.