Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
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can't exceed 260ºC, with the peak temperature no more than 300ºC.
2) Measurement analysis
3. Variable nozzle turbocharger (VNT) control
1) Overview
z HFC4DA1-2C adopts variable section turbocharger technology so that the turbocharger and the engine are well
matched under all working conditions to realize best engine performance.
z The blades of the VNT are connected to the control tie rod and the displacement of the control tie rod is
controlled by the vacuum pressure of the vacuum chamber on the VNT. Changing the vacuum pressure of the
vacuum chamber can change the position of VNT blades and control the flow area of the turbine. The vacuum
pressure of the vacuum chamber is controlled by VNT solenoid valve, of which one port is connected to the
vacuum chamber on the VNT, one port is connected to the vacuum pump, and another port is connected to the air.
This connector in the engine is additionally fitted with filter to prevent the ingress of contaminant (such as dust)
into the valve. The open extent of the VNT solenoid valve is regulated by the PWM wave issued by ECU and the
solenoid valve is installed on the crossbeam of the body water tank.
2) Measurement analysis
4. Fuel metering unit
1) Overview
The fuel metering unit is located on the high pressure fuel pump and is functioned to control the fuel amount from the
low pressure pump to the high pressure pump.
2) Working Principle
The fuel metering valve is installed at the high pressure fuel inlet of high pressure fuel pump and is functioned to
regulate the fuel supply amount and fuel pressure, of which the regulation requirement is subject to the control of
ECU. The control coil of the metering valve is closed when not electrified, which cuts off the fuel supply to the
plunger of high pressure fuel pump. The ECU changes the fuel inlet section area of metering unit by means of pulse
signal to increase or reduce the fuel supply amount.
3) Measurement analysis
Wiring terminals: 1 – Signal terminal; 2 – 12V voltage.
EGR power supply
EGR position signal
EGR signal grounding
EGR control signal terminal
EGR control grounding
terminal
EGR passage section
EGR actuator
Turbocharger actuator
Turbocharger control signal
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