A Fuel metering valve opened to maximum
B Fuel metering valve opened to minimum
V Voltage
a Low duty cycle
b High duty cycle
1 Transfer pump
2 Fuel metering valve
3 Fuel flow to the high-pressure chambers
Function
NOTE: The fuel metering valve operates together with the fuel pressure sensor (on the fuel rail) in a closed control loop.
NOTE: The fuel metering valve is fully open when de-energized.
The fuel quantity that passes to the high pressure chambers of the high pressure pump is dependent on the opening cross section of the fuel metering valve.
The opening cross-section is determined by the PCM via the duty cycle of the PWM signal:
• Low duty cycle: large aperture cross-section
• High duty cycle: small aperture cross-section
Effects of faults
In the event of malfunctions: Injected quantity = 0 (engine cuts out or cannot be started.)
Diagnosis
The monitoring system checks:
• the circuit for short circuits and open circuit.
• the fuel metering valve for correct function; the values of the fuel pressure sensor are used for this purpose. The currently measured values from the fuel pressure sensor are continuously compared with the map data. Slight deviations are indicated as control faults whereupon:
– the quantity of fuel injected is reduced and
– the pilot injection is deactivated.
• whether serious deviations exist. They are indicated as a malfunction whereupon
– the quantity injected is set to 0 and the engine is stopped.
Note: Control faults do not necessarily mean a defective fuel metering valve or a defective high pressure pump. A blocked fuel low pressure system or defective fuel injectors could (among other things) also be the cause.
Emissions-related component (vehicles with EOBD):
• Yes (MIL-active), with control faults
• No (Non MIL active), with malfunctions.
