Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
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Chapter III Working Principle of Engine Control and Actuator Units
Section I Overview of Diesel Common Rail System
The electronically controlled high pressure common rail system means one fuel supply mode in which the generation
of injection pressure and fuel injection are completely separated in the closed-loop system composed of high pressure
fuel pump, pressure sensor, and ECU. The high pressure fuel pump generates high pressure fuel and conveys to the
common rail pipe to realize precise control of fuel pressure within the common rail pipe. This fuel injection system
can ensure that the fuel injection pressure will not vary following the variation of the engine speed and thus relieve the
defect of traditional diesel engines. Instead of the common pulse theory, this system adopts the pressure-time
measuring theory and combines the high pressure common rail with the control of fuel injection solenoid valves of all
cylinders, in which the last pulse of the control unit introduces the injection signal into the solenoid valve to trigger
one injection cycle and the injection amount is controlled by the accumulated pressure and the open duration of the
injector. The injection pressure of EDC17 control system adopted by this engine is up to 1,600bar.
The electronically controlled common rail fuel injection technology of diesel engine integrates the computer control
technology, modern sensing and measuring technology, and advanced fuel injection mechanism. The main
characteristic of this technology is as below: The main parameters (including speed, torque, power, oil temperature, oil
pressure, water temperature, and turbocharger pressure of the diesel engine) under actual working conditions of the
diesel engine are measured by modern sensing and measuring technology and transmitted to the ECU and the ECU
compares these measurements with the pre-inputted optimized running MAPs of the diesel engine and processes and
calculates out the best values to control the pressure of common rail pipe and the open moment, duration, and
injection frequency of the high speed solenoid valves of the fuel injectors, in order to realize the best working state of
the diesel engine. The electric pulses generated by the ECU trigger the solenoid valves of the fuel injector as per
specified sequence to determine the open and close moments of each fuel injection cycle of the engine and flexibly
control the fuel injection speed and frequency. The common rail fuel injection mechanism forms directly or indirectly
constant high pressure fuel and distributes to each fuel injector. The electronically controlled common rail fuel
injection technology of the diesel engine can guarantee that the diesel engine achieves the best air-combustion ratio
and excellent atomization.
Diesel common rail injection system
High pressure
pump
Cut-off valve
(optional)
Fuel pressure sensor
Distribution
pipe
Fuel-water
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