High-pressure fuel circuit, function

W07.16-1067-76

The fuel delivered by the fuel pump and cleaned by the fuel filter module flows via the quantity control valve (Y642) to the fuel system high pressure pump (1).

The engine management (MCM) control unit (A4) determines the fuel quantity which is fed into the fuel system high pressure pump (1) via the quantity control valve (Y642) depending on the operating condition of the engine.

The fuel is compressed by the fuel system high pressure pump (1) and delivered via the two high-pressure lines (2) to the rail (3). The fuel pressure of approx. 900 bar that is generated in this way is detected by via the rail pressure sensor (B622) and transmitted to the engine management (MCM) control unit (A4).

If the maximum permissible fuel pressure is exceeded, the mechanical pressure limiting valve (5) opens and the excess fuel flows back via the fuel return line from the pressure limiting valve (7) to the fuel filter module in the low-pressure fuel circuit.

The highly compressed fuel passes from the rail (3) to the fuel injectors for cylinder 1 to 6 (Y608 to Y613) via the fuel high-pressure lines (4).

From fuel injectors for cylinders 1 to 6 (Y608 to Y613) the fuel is injected, according to the injection variant, with or without additional pressure amplification into the respective cylinder. The injection pressure can be up to 2,100 bar.

The injection quantity, the injection timing point and the relevant injection variants are determined by the engine management (MCM) control unit (A4) depending on the operating condition of the engine.

The diverted quantity of the solenoid valves at the nozzle needles and the diverted quantity of the solenoid valves at the pressure converters pass over the two fuel return lines of the fuel injectors (6) back to the fuel filter module and therefore back into the low-pressure fuel circuit.