Fuel Supply, High-Pressure Side DFI

Fuel Supply, High-pressure Side DFI







In the high-pressure system, a variable pressure is generated when the engine is running. It is regulated between 435 psi (30 bar) and 1740 PSI (120 bar) depending on the engine load.







The following components are used:
- Fuel high-pressure pump with quantity control valve for fuel pressure, integrated pressure control valve and fuel pressure sensor for low pressure
- High-pressure fuel line to the fuel rail (distribution pipe)
- Fuel rail (distributor pipe)
- Fuel pressure sensor for high pressure
- Fuel injectors







Fuel high-pressure pump










The high-pressure pump is driven with a triple cam on the intake camshaft. To keep the friction between the pump tappet and camshaft as low as possible, the movement is transmitted using roller tappets. The quantity control valve facilitates demand-based regulation of the fuel high pressure between 435 psi (30 bar) and 1740 PSI (120 bar). If the quantity control valve on the high-pressure pump is not activated, the fuel is pumped to the high-pressure fuel system. The pressure control valve is integrated into the fuel high-pressure pump and protects the components against too high a fuel pressure in the event of thermal expansion or malfunctions. It is a spring-loaded valve and opens from a fuel pressure of 2030 psi (140 bar). When the valve opens, the fuel flows from the high-pressure side of the pump back to the low-pressure side.

Fuel pressure sensor, high pressure







The fuel pressure sensor is screwed into the fuel distribution pipe. It measures the fuel pressure in the high-pressure fuel system and sends the signal to the engine control unit.

Signal utilization

The engine control unit evaluates the signals and regulates the high pressure in the fuel rail via the quantity control valve for fuel pressure.

Effects in the event of failure







If the fuel pressure sensor detects that the nominal pressure can no longer be regulated, the fuel pressure regulating valve is permanently activated during compression and is open. The fuel pressure is thus reduced to 72.5 psi (5 bar) of the low-pressure fuel system (emergency operation).

If the fuel pressure sensor fails, the fuel pressure regulating valve is permanently activated during compression and is open. The fuel pressure is reduced to approx. 83 psi (5.7 bar) of the low-pressure fuel system. As a consequence, engine torque and power output are drastically reduced.