Fuel Supply, Function - GF07.10-P-1003MRT
Engine 256.9 in model 213, 238, 257, 290
up to model year 2021
Engine 256.9 in model 222
Function requirements, general
- Circuit 15 (ignition ON)
Electronic ignition lock control unit (N73) transmits the circuit status via the suspension FlexRay (Flex E), powertrain control unit (N127) and drive CAN (CAN C1) to the ME-SFI [ME] control unit (N3/10).
Fuel supply, general points
The fuel supply supplies filtered fuel out of the fuel tank in adequate amounts under all operating conditions at an adequate pressure to the fuel system high pressure pump.
The fuel supply system is subdivided into the following points:
- Fuel low-pressure circuit
- Fuel high-pressure circuit
- Safety fuel shutoff
Fuel low-pressure circuit
The low-pressure fuel circuit ensures the fuel supply of the fuel high-pressure pump.
The ME-SFI [ME] control unit transmits the "Fuel pump ON (M3)" request via a direct line and redundantly via the drive CAN to the fuel system control unit (N118). The ME-SFI [ME] control unit also transmits the specified fuel pressure via the drive CAN to the fuel system control unit. The ME-SFI [ME] control unit calculates the specified fuel pressure (fuel requirement) from the current fuel pressure and the load requirement of the engine. Depending on the fuel requirement, with fuel pressure of approx. 4 to 6.7 bar, a fuel delivery volume of 0 to 130 l/h is regulated in this way.
The fuel system control unit accordingly actuates the fuel pump, evaluates the fuel pressure and transmits this via the drive CAN to the ME-SFI [ME] control unit. The fuel pressure is recorded by the fuel pressure sensor (B4/7). The fuel system control unit reads in the signals of the fuel pressure sensor directly.
The fuel pump suctions the fuel out of the fuel feed module and pumps it through the fuel filter to the high pressure fuel pump (single line system, without return line). The overflow valve in the fuel filter opens at a fuel pressure of approx. 7 to 9 bar. A check valve is located in the fuel filter feed line that prevents a decrease in the fuel pressure (to below 4.5 bar) where the fuel pump is OFF.
The fuel pressure sensor also records the fuel temperature.
Fuel high-pressure circuit
In the fuel high-pressure circuit, the fuel high pressure of about 200 bar that is required for spray-guided direct injection is generated, regulated and stored in the rails.
The quantity control valve (Y94) is installed on the fuel high-pressure pump. The quantity control valve regulates the fuel quantity that is supplied to the pump element in the fuel high-pressure pump in a demand-and characteristics map-dependent manner. The ME-SFI [ME] control unit evaluates the signals of the fuel pressure and temperature sensor (B4/25) for this purpose.
The ME-SFI [ME] control unit accordingly actuates the quantity control valve. The fuel pressure and temperature sensor is installed on the rail.
The fuel high-pressure pump supplies the fuel via the high-pressure line and rail to the following components of the fuel injection system that are then accordingly actuated by the ME-SFI [ME] control unit:
- Cylinder 1 fuel injector (Y76/1)
- Cylinder 2 fuel injector (Y76/2)
- Cylinder 3 fuel injector (Y76/3)
- Cylinder 4 fuel injector (Y76/4)
- Cylinder 5 fuel injector (Y76/5)
- Cylinder 6 fuel injector (Y76/6)
In engine idle and for selector lever position "N" or "P", the pressure is reduced to approx. 130 bar to reduce the noise emission of the fuel high-pressure pump.
When a hot engine is stopped, the fuel pressure can increase to as much as 250 bar (+17 bar). In this case, the quantity control valve at the fuel high-pressure pump is opened and the pressure reduced.
During regulation of the fuel high-pressure circuit one differentiates between the following operating conditions:
- Start
- Normal mode
- Low-pressure limp-home mode (fuel high pressure is not reached)
- Stop
Start
The quantity control valve is energized and is thus closed. The fuel high-pressure pump delivers at maximum capacity. The pressure in the rail is quickly built up. The fuel pump pressure is 4.5 to 6.7 bar at the low-pressure side.
Normal mode
The ME-SFI [ME] control unit actuates the quantity control valve in a pulse width modulated manner and thus regulates the required fuel quantity. On the low-pressure side, the fuel pump pressure is 4.5 to 6.7 bar (depending on engine speed and fuel temperature).
Low-pressure limp-home mode (fuel high pressure is not reached)
The quantity control valve is not energized and is thus opened. The fuel pump pressure is 4.5 to 6.7 bar. Fuel flows via the open quantity control valve into the rail. The fuel injectors are actuated for longer. In low-pressure limp-home mode, the engine is operated in an output reduced manner. The maximum vehicle speed is 70 km/h.
Stop
The quantity control valve is not energized and is thus opened. The fuel pressure in the rail in reduced. The fuel pump is no longer actuated.
Fuel high-pressure system
Safety shutoff
In the event of an accident, the ME-SFI [ME] control unit switches the engine off and stops the fuel supply.
The Supplemental Restraint System control unit (N2/10) transmits the crash signal via a direct line (analog) and also via the user interface CAN (CAN HMI), electronic ignition lock control unit, suspension FlexRay, powertrain control unit and engine CAN (CAN C) to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit then ends the actuation of the fuel injectors, quantity control valve and fuel pump. The engine is switched off, and the ME-SFI [ME] control unit reads in the crankshaft Hall sensor (B70) signals directly. The fuel pressure is reduced in the fuel high-pressure circuit. There is less risk of fire after an accident.
| Electrical function schematic for fuel supply | Engine 256.9 in model 213, 238 up to model year 2021 | PE07.10-P-2703-97DBA | |
| Engine 256.9 in model 222 | PE07.10-P-2703-97SEM | ||
| Engine 256.9 in model 257 up to model year 2021 | PE07.10-P-2703-97XBB | ||
| Electrical function schematic for safety fuel shutoff | Engine 256.9 in model 213, 238 up to model year 2021 | PE07.10-P-2733-97DBA | |
| Engine 256.9 in model 222 | PE07.10-P-2733-97SEM | ||
| Engine 256.9 in model 257 up to model year 2021 | PE07.10-P-2733-97XBB | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MRT |