Engine JAC HFC4DA1-2C. Manual — part 19

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

75

The space of the common rail is always filled with high
pressure fuel. It utilizes the fuel compressed due to high
pressure to achieve the accumulator effect. When the fuel is
departed from the common rail for injection, the pressure in the
high pressure accumulator is basically constant. At the same
time, the pressure variation generated by the pulsed fuel supply
of high pressure pump is balanced and the pressure information
is provided to the ECU.

IV. High pressure fuel pipe

The high pressure fuel pipe is used to convey the high pressure
fuel and is made of steel to endure the intermittent high
frequency pressure variation under the maximum system pressure of the engine. The fuel pipe is generally 6mm in
outside diameter and 2.4mm in inside diameter. All high pressure fuel pipes between fuel rail and fuel injectors are
same in length, which means that the distances between the fuel rail and all fuel injectors are the same and the bending
points compensate the corresponding length differences.

IV. Fuel injector

The fuel injectors are the core parts of the high pressure common rail and are installed on the high pressure common
rail. In accordance with the directive of the ECU, the fuel
injectors spray high pressure well-atomized fuel into the
combustion chamber at specified moment and specified
pressure for a specified duration.

The fuel injector is mainly composed of fuel injector
nozzle, hydraulic servo unit, and solenoid valve. When
the coil control valve acquires control signal through the
ECU, the control valve will depart from its seat ring so
that the fuel pressure in the needle valve control chamber
drops rapidly. As the pressure at the injector nozzle holder
is maintained at similar pressure with common rail, the
needle valve opens and the injection starts. When the
current of the solenoid control valve drops to zero, as the
control valve returns to the seat cushion under the
application of coil spring, the pressure of the needle
control chamber will increase to lightly higher than he
pressure at the injector holder so that the needle valve
closes the injector and the injection stops. The sealing
copper washer beneath the fuel injector must be replaced
once the fuel injector is disassembled or loosened. During
the disassembly, use the special tools recommended or
designated by JAC Multifunctional Commercial Vehicle
Company. Note: Never disassemble the fuel injector by
self in any case. All maintenances and services of the fuel
injector body shall be fulfilled by Bosch relevant service
stations or JAC designated service stations.

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

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Section IV Electronic Control Unit of High Pressure Common Rail System

The EDC17 system of HFC4DA1-2C engine belongs to electronically controlled diesel injection system and
incorporates the dynamic fuel injection timing system and air and fuel management system. It adopts the BOSCH
diesel high pressure common rail system, with the rail pressure up to 1,600bar, and applies new technologies
including VNT, electronically controlled EGR, and POC pressure difference control to meet the Euro-IV emission
standard, with potential compliance for Euro-V emission standard.

The characteristics of this system is one single ECU, one set of fuel injection control system, and one set of sensor
system. It’s functioned to inject the fuel into the engine cylinder, with accurate injection timing and fuel amount, so
that the fuel is mixed with air in the cylinder to achieve best combustion efficiency.

The electronic control unit of the diesel common rail system is mainly composed of three parts: sensor, ECU, and
actuator.

① Sensor part: The sensors and rated value transmitters collecting the running state and rated values of the engine
and complete vehicle, which convert various types of physical parameters into electric signals.

② ECU: It’s functioned to process the information as per definite mathematic calculation method and issue the
electric signals of the directives.

③ Actuator: It’s functioned to convert the electric signals of the directives issued by the ECU into mechanical
parameters.

I. Sensor part

1. Crankshaft position sensor

1)

Overview

z The crankshaft position sensor is one electromagnetic sensor.

z The position of piston in the combustion chamber determines

the start moment of fuel injection. As the engine piston is
connected with crankshaft through connecting rod, the
crankshaft position sensor can provide all data information for
the piston position and the engine speed determines the
revolution per minute of the crankshaft.

z Generation of signal: The crankshaft is connected with one

60-tooth ferromagnetic actuation gear. The actuation gear
actually in use has two teeth missing. This large gap
corresponds to one specified crankshaft position of 1

st

cylinder.

The crankshaft position sensor records the tooth sequence of
the actuation gear. It’s composed of one permanent magnet and
soft iron core with copper coil. The magnetic flux in the sensor
varies along with the gear and gap passing through and
generates one sine AC voltage, of which the amplitude rapidly
increases following the speed of the engine (crankshaft). It can
achieve sufficient amplitude even when the speed is at 50r/min.

z The crankshaft position sensor is situated on the rear clutch

housing of the engine;

z Wiring terminals: 1. Signal terminal of crankshaft position

sensor; 2. Grounding terminal of crankshaft position sensor;

Crankshaft speed sensor
1. Permanent magnet 2. Sensor housing
3. Engine outer cap 4. Soft iron core
5. Coil 6. Sensing gear

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

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z Resistance: 860 Ohm;

z Clearance between sensor and top of signal gear: 0.5~1.2mm.

2) Working Principle

The electromagnetic sensor simulates the AC signal generator, namely such sensor generates AC signal, and is
generally composed of a magnet wound by coil and two wiring terminals. These two coil terminals are the output
terminals of the sensor. When the steel annular gear (sometimes referred to as magnetic resistance gear or target gear
or signal gear) rotates to pass through this sensor, the magnetic flux of the magnet passing through the coil varies at
certain level and the induction voltage is generated in the coil.

The same tooth profiles of the signal gear will generate continual pulses in same form. The pulses have consistent
form amplitudes (peak-peak voltages) and are in proportion to the speed of crankshaft signal gear. The frequency of
the output signal is based on the rotation speed of the magnetic resistance gear and the air gap between sensor
magnetic pole and the magnetic resistance gear is of great influence over the amplitude of the sensor signal (Attention
shall be paid to the backlash during the installation). During the production, removing the synchronous pulse
generated by one tooth or two really close teeth from the sensor can determine the signal of top dead center, which
will lead to the frequency variation of output signal. When the number of teeth is reduced, the voltage output
amplitude will vary greatly. This pulse signal is transmitted to the ECU, based on which the ECU controls the fuel
injection of the engine.

As the electromagnetic crankshaft position sensor is weak in signal and sensitive and is vulnerable to the
electromagnetic interference by the electric devices such as car telephone, fan, and starter, it will lead to malfunction
of traveling performance or generate trouble code. To prevent the occurrence of such phenomenon, two signal wires of
the crankshaft position sensor adopt the twisted-pair structure in the manufacturing of engine harness, which can
effectively guard the signal of crankshaft position sensor against the external signals and reduce the production cost.

3) Measurement analysis:

1 – Signal -; 2 – Signal +; Use a multimeter to measure the resistances for two signal terminals of the crankshaft
position sensor. The resistance measurement shall be 860 Ohm.

4) Malfunction Mode:

z Short-circuit or open-circuit of sensor;

z Distorted, error, and suspicious signal;

z Unstable sensor signal;

z Sensor signal is out of range.

The crankshaft position and speed sensor is the main sensor of the engine electronic control system. In event of the
malfunction of crankshaft position and speed sensor, the engine can’t start. If the malfunction occurs after the start of
the engine, the engine will stop immediately.

5) Troubleshooting

Speed sensor

Signal

Grounding

Shielding wire

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

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Use diagnosis instrument to check the trouble code and determine the
malfunction position. Mainly check whether the sensor is installed in place and
whether the clearance is normal, check the sensor circuit whether there is
short-circuit or open-circuit to grounding wire, check whether there is
short-circuit or open-circuit to the power supply, and check whether the circuit
is consistent with the given pin definition.

Notice: Take caution to install the sensor and make sure not to add any washer,
or it may lead to signal distortion of sensor.

2. Camshaft position sensor

1) Overview

z The camshaft position sensor is one Hall sensor.

z The camshaft position sensor utilizes the Hall effect to determine the camshaft position. One steel actuation gear

rotates along with the camshaft, the Hall effect integrated circuit is installed between actuation gear and
permanent magnet, and the permanent magnet generates a magnetic field perpendicular to the Hall unit. If one
tooth of actuation gear passes through the current-carrying linear sensor unit (semiconductor chip), it changes the
strength of magnetic field perpendicular to the Hall unit. In such case, the electron driven by the voltage in major
axis direction is offset in the direction perpendicular to the current direction to generate one temporary signal
voltage (Hall voltage) so that the calculation circuit integrated with the sensor Hall integrated circuit will process
the signal and output as square wave signal.

z The camshaft position sensor is installed on the cylinder head shield.

z Wiring terminals: 1. +5V power supply, 2. Signal output, 3. Grounding;

z The clearance between sensing end of sensor and the signal gear of camshaft: 0.5~1.5mm. Required torque:

8

±0.5Nm

2) Working Principle

The camshaft controls the intake and exhaust valves of the engine, of which the speed is only half of the crankshaft
speed. When the piston moves towards the top dead center, the camshaft position determines whether the piston is at
compression stroke or the exhaust stroke and then judges the fuel injection or not. If the engine is under start stage,
such data information can’t be acquired from the crankshaft position. On the other hand, during the normal working
of the engine, the data information generated by the crankshaft sensor is enough to determine the engine state. In
other words, while the vehicle is traveling, even the camshaft sensor is failed, the ECU can still receive the data
information of engine working state from the crankshaft sensor.

The camshaft sensor utilizes Hall effect to determine the camshaft position. One steel toothed part is fixed on the
camshaft and rotates along with the camshaft. When this toothed part passes through the semiconductor chip of the
camshaft sensor, its magnetic field will offset the electron of the semiconductor chip towards the current direction.
Therefore, one temporary voltage signal (Hall voltage) is generated to remind ECU that the 1

st

cylinder enters into the

compression stroke.

3) Measurement analysis

Wiring terminals: 1 - +5V, 2 – Signal +, 3 – Grounding

Camshaft

position

sensor

Grounding terminal

Signal terminal

Power supply terminal