JAC HFC4DA1-2C engine. Service Manual — part 5

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section passage is greatly higher than that passing through the constant section passage.

Idling of

engine

Small passage

section

Large passage

section

High speed

running of engine

Rotation direction of adjustment ring

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Section IX EGR System

The exhaust gas recirculation (EGR) introduces one small portion of exhaust gas from the exhaust pipe into the intake
pipe that is mixed with the fresh intake air to artificially increase the exhaust amount in the fresh intake air and thus
reduce the combustion temperature of engine and reduce the formation of NOx.

z The NOx is increased following the increasing of engine load and the EGR ratio shall increase accordingly.

z The EGR is not be performed when the engine coolant temperature is low;

z The EGR is not performed under idling or low load, as the NOx emission is not high in such case.

z The EGR is not performed under full load or acceleration;

z The water-cooled EGR further reduces the temperature of exhaust gas entering into the cylinder and further

reduces the emission of NOx.

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Section X Exhaust System

The exhaust pipe is composed of four exhaust manifolds leading to the exhaust master pipe and one manifold leading
to the exhaust gas chamber of EGR valve. During the operation, the exhaust gas from the combustion chamber is
introduced into the EGR valve by the manifold leading to the exhaust gas chamber of EGR valve through the EGR
passage in the cylinder head. Under the control of the EGR valve, the exhaust gas is mixed with fresh air and enters
into the combustion chamber to realize exhaust gas recirculation and reduce the emission.

4DA1-2C diesel engine real-time monitors the pressure drop of the exhaust gas post-treatment unit to determine
whether the post-treatment system is working normally. Via two pressure ports on the sensor, the pressure on two
sides of the exhaust gas post-treatment unit is introduced. The sensor converts the measurement into voltage value and
feeds back to the control unit, which can guarantee the sufficient oxidization of grains and prevent the blockage of
catalytic converter.

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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

t

Fuel tank

High pressure

Low pressure

Pressure

regulation valve

Fuel temperature

sensor

Fuel delivery pump

Other sensors

Accelerator
pedal

Fuel injector

Crankshaft
position
sensor

Camshaft position
sensor

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The high pressure common rail system is composed of fuel tank, diesel filter, high pressure fuel pump, common rail
pipe, electronically controlled fuel injector, high pressure fuel pipe, and low pressure fuel return pipeline.

z It adopts direct injection combustion chamber system and common rail fuel supply system to realize high

performance, clean emission, low noise, and low vibration;

z Single camshaft and four-valve technology brings about higher air charging efficiency and improves the

combustion;

z High power per liter design and compact design;

z Variable nozzle turbocharger (VNT) control;

z Exhaust Gas Recirculation (EGR);

z Electronic throttle control.

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Section II Working Principle of Low Pressure Fuel Line System

I. Composition of low pressure fuel line:

The low pressure fuel line is functioned to supply sufficient fuel to the
high pressure fuel line and is composed of:

z Fuel tank (including filter screen)

z Fuel filter (including manual fuel delivery pump)

z Low pressure fuel delivery pump

z Other low pressure fuel hoses

II. Fuel tank

The fuel tank shall be fabricated from anti-corrosion material and shall maintain 0.3bar pressure under all working
conditions and be free of fuel leakage under the application of the doubled working pressure. The fuel tank shall also
set up appropriate opening or safety valve or adopt appropriate measures to relieve the excessive pressure whenever
it's needed. When the motor vehicle is subject to slight vibration, makes turns or travels or parks on a slope, the fuel in
the fuel tank shall not leak from the fuel tank cap or the pressure balancing device.

III. Fuel filter (including manual fuel delivery pump)

Sunray long-wheelbase model adopts two-stage diesel filter, including
one primary filter and one fine filter. Compared with traditional diesel
engines, it requires cleaner fuel supply. The impurities contained in
the fuel will damage the fuel system including the high pressure pump,
high pressure common rail, and fuel injector. The fuel filter purifies
the fuel inputting into the high pressure fuel pump, in order to help the
normal functioning of the high pressure pump. The contaminant,
impurity, and particle in the fuel will lead to the damage of pump units,
fuel supply valve, and fuel injector. Therefore, the use of fuel filter
capable of meeting the fuel injector requirements becomes the
premise for normal working of the engine and guarantee of service life.
The water content in the diesel may exist in non-free radical form
(emulsified fuel) or radical form (such as water condensate generated
due to variation of temperature). If entering into the fuel injection
system, this water content will lead to damage of parts due to corrosion.
Similar to other fuel injection systems, common rail system requires
the fuel filter with water collection chamber as well as the automatic
water content alarm. When the alarm lamp lights up, make sure to
drain the water from the water collection chamber.

The fuel filter is composed of fuel temperature sensor, fuel heater,

manual fuel pump, fuel-water separator, and water level sensor.
The fuel leakage during traveling or the air ingress into fuel pipeline
after replacement of fuel filter may lead to start failure or poor
functioning of the engine. Therefore, make sure to bleed the air from
the low pressure fuel pipeline after the installation of manual fuel
delivery pump. Installed on the fuel filter, the manual fuel delivery
pump is the device for supplying fuel to the fuel filter and the device
required to guarantee the first start of the engine. In event of the
following conditions, press the manual fuel delivery pump, till the
manual fuel delivery pump can’t be further pressed, before starting the

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engine.

z After the fuel is used up.

z After the water drainage from the fuel-water separator.

z After the replacement of fuel filter

Replacement of fuel filter

1. Replacement interval of fuel filter: Once every 7,000km;

2. Water separation interval: Once every 5,000Km;

3. It’s prohibited to use any used fuel filter.

IV. Low pressure fuel delivery pump

The low pressure fuel delivery pump is one gear pump and is stalled
at the rear end within the high pressure pump housing. The low
pressure fuel delivery pump continually supplies the required fuel
amount to the high pressure pump from the fuel tank.

The fuel delivery pump is functioned to supply sufficient fuel
supply to the high pressure pump under following conditions:

(1) Under any working condition;

(2) Under necessary pressure;

(3) Throughout the entire service life.

The low pressure fuel delivery pump is one mechanical gear pump and is installed at the rear end of high pressure
pump and driven by the high pressure pump shaft. Its main parts are two gears rotating in opposite direction. While
rotating, two gears engages to vacuumize the fuel into the chamber formed between gears and pump walls and then
conveys to the outlet (pressure end). The closing line of the rotating gears realizes the sealing between vacuumization
end and pressure end of the pump and prevents the fuel backflow.
The fuel supply amount of the gear pump is approximately in proportion to the engine speed. This is why the fuel
supply amount of the gear pump can be reduced by means of the throttle valve at the inlet end or can be restrained by
means of the relief valve at the outlet end.
No maintenance is required for the gear pump. Charge the fuel from the fuel system before the first start. When the
fuel in the fuel tank is used up, operate the manual fuel delivery pump to charge fully the low pressure fuel line.

V. Fuel pipeline

Besides the steel pipe, the low pressure fuel line can also adopt flame-retardant braided and armored fuel hose. The
fuel pipes shall be arranged in such manner to prevent the mechanical damage and that the fuel dripped or evaporated
will not concentrate nor burn.

In event of vehicle distortion, engine displacement, or similar conditions, the functions of the fuel pipeline shall not be
impaired. All fuel delivery pipelines shall have the radiation shield measures.

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VI. Common malfunctions and troubleshooting for low pressure fuel line

No. Malfunction

Troubleshooting

Remarks

1

Weak pumping of
fuel

Retighten the connectors (temperature
sensor, plug, and pile connector), in
order to prevent the pumping failure
due to ingress of air. If ineffective,
replace the manual pump.

The tightening torque for connectors is
30-35N.m. Higher torque will lead to
thread failure.

2

Fuel leakage of air
bleeding screw

Check the screw hole of manual pump
for presence of thread failure. If yes,
replace the transitional thread insert
and air bleeding screw and washer.

The tightening torque is 7~9N.m. Higher
torque will lead to thread failure. While
assembling the transitional thread insert,
add an appropriate amount of thread sealant
onto the thread. Prevent the ingress of
sealant into the manual pump.

3 Fuel

leakage

of

manual pump

Replace the manual pump

The knocking or improper use will lead to
fuel leakage of manual pump

4 Slow

acceleration

and difficult start
due to difficult
fuel supply

The filter is blocked. Replace the filter.
If the malfunction still occurs after
replacement of fuel filter, check other
engine parts.

The blockage of fuel filter will increase the
pressure difference.

5

Failure for timely
water drainage

Make sure to drain the water when the
water level sensor indicator lamp lights
up.

If the water is not drained, the water
content in fuel will increase to impair the
engine performance.

6

Light-up failure of
water level sensor
indicator lamp at
engine start

1. Water level sensor is damaged.

2. Indicator lamp is damaged.

3. Circuit malfunction

7

Working failure of
heater

1. The heater is damaged.

2. Circuit malfunction

3. Low battery current

4. The heater is punctured due to high
current

8

Working failure of
temperature
sensor

Damage o temperature sensor

Circuit malfunction

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Section III Working Theory of High Pressure Fuel Line

I. High pressure fuel line parts

The high pressure fuel line generates and accumulates
sufficient fuel pressure required for the fuel injectors.
The parts include: High pressure pump, fuel rail, high
pressure fuel pipe, and fuel injector.

II. High pressure pump

The high pressure pump compresses the fuel to a system
pressure of up to 1,450bar and then the fuel is
transmitted to the tubular high pressure fuel accumulator
(rail) via the high pressure pipe.

The high pressure pump is the interface between low pressure stage and high pressure stage. Under all working
conditions, it can reliably supply sufficient high pressure fuel throughout the entire service life of the vehicle,
including supplying addition fuel required for rapid start and the
rapid establishment of pressure in the common rail. The high
pressure pump continually generates the system pressure required
for the high pressure accumulator (rail). Therefore, it means that,
compared with traditional system, it’s unnecessary to compress the
fuel for each individual injection cycle.

The fuel is compressed by three plunger pumps arranged radially at
spacing of 120º from each other. As each rotation turn can generate
three compression strokes and only generate low peak drive torque,
the drive unit of the pump maintains uniform force application. As
far as 16Nm torque is concerned, this torque is only 1/9 of the
torque required for driving similar distribution pump. This means
that, compared with traditional fuel injection systems, the common rail generates lower load onto the drive unit of the
pump. The raising power of the drive pump is in proportion to the preset pressure of common rail and the speed of the
fuel pump (fuel delivery amount).

Working mode:

Through one water separator, the fuel delivery pump pumps out the fuel from the fuel tank and the fuel enters into the
lubricating and cooling lines of high pressure pump via the fuel inlet. The drive shaft with eccentric wheel drives three
pump plungers for upward and downward movements along with the profile of the cam. The pump plungers move
downward under the application of the fuel delivery pressure (fuel suction stroke). When the plungers overpass the
bottom dead center, the fuel inlet valve is closed so that the fuel in the pump chamber will not leak out. In such case,
the fuel is compressed so that the fuel pressure exceeds the fuel delivery pressure of the fuel delivery pump. In such
case, once the pressure established exceeds the pressure in the common rail, the fuel outlet valve opens so that the fuel
enters into the high pressure line. The pump plungers will continue the fuel supply, till the top dead center is reached
(fuel delivery stroke). Then the pressure drops and the fuel outlet valve closes. The residual fuel is pressure relieved:
The pump plungers move downward. When the pressure in the pump chamber is less than the fuel delivery pressure,
the fuel inlet valve re-opens and the pumping process is started again.

III. Fuel rail (Common rail)

The high pressure accumulator (rail) stores the high pressure fuel and at the same time restrains the pressure variation
generated during the fuel supply and fuel injection of the high pressure pump. The high pressure accumulator is
shared by all cylinders and therefore is referred to as “common rail”. Even when a great amount of fuel is drained, the
common rail can maintain its internal pressure basically unchanged. Therefore it maintains the constant fuel injection
pressure of the fuel injector.

1.

Drive shaft

2.

Eccentric cam

3.

Plunger pump

4.

Fuel suction valve

5.

Fuel outlet valve

6.

Fuel inlet

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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.

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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

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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

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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

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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.

5) Troubleshooting

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.

3. Pressure difference sensor

1) Overview

z The pressure difference sensor is functioned to real-time monitor the pressure drop of the POC and determine

whether the after-treatment system is working normally. The pressure at two ends of the POC is introduced via
two pressure ports of the sensor and then the sensor converts the measurement into voltage value and feeds back
to control unit. This can not only guarantee the sufficient oxidization of grains, but also prevent the blockage of
catalytic converter.

z The pressure difference sensor and the POC are connected via stainless steel pipe and high temperature rubber

hose. The pressure is introduced via stainless steel pipe, which is at least 250mm in length, from two sides of
POC and then is led to the pressure difference sensor via high temperature rubber hose, which is capable of
enduring more than 150ºC.

2) Working Principle

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3) Test analysis

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

3. Turbocharger pressure sensor

1) Overview

The turbocharger pressure sensor is connected to the
intake pipe and is functioned to measure the absolute
pressure of the intake pipe. This sensor is composed of
one pressure unit with two sensing units and one
evaluation circuit chamber. The sensing units and
evaluation circuit are mounted on common ceramic
substrate. Each sensing unit incorporates one horn-shaped
diaphragm embodying the benchmark capacity for
determination of internal pressure. The diaphragm moves
towards large or small open extent as a function of
charging pressure. The pressure sensitive resistor is
mounted on the diaphragm surface, of which the resistance
varies under the application of pressure. These resistors are
connected to form a resistor bridge. Therefore, any
movement of the diaphragm will change the balance of
resistor bridge, namely the voltage of the resistor bridge is
one measurement of turbocharger pressure. The evaluation
circuit is functioned to amplify the bridge voltage and
compensate the linear variation of temperature influence
and pressure characteristic. The output signal of evaluation
circuit is transmitted to ECU and then the turbocharger
pressure is obtained by means of the programming
characteristic curve.

z The temperature sensor incorporates one negative

temperature coefficient (NTC) thermistor that is
connected in the voltage division circuit of 5V power
supply.

z The voltage drop on the resistor is inputted to the ECU via one analog and one digital converters (ADC), which

is one measurement for evaluating the temperature. The ECU micro-processor embodies one characteristic curve,
which defines the temperature as a function of given voltage.

z It’s installed on the pressure stabilizing chamber of intake manifold and take the priority to measure the pressure.

z Wiring terminals: 1 – Grounding, 2 – Temperature signal, 3 – +5V, 4 – Pressure signal.

2) Working Principle

The turbocharger pressure sensor is connected in the intake pipe and is capable of measuring the absolute pressure of
intake pipe at 0.5~3bar. This sensor is composed of one pressure unit with two sensing units and one evaluation circuit
chamber. The sensing units and evaluation circuit are mounted on common ceramic substrate. Each sensing unit
incorporates one horn-shaped diaphragm embodying the benchmark capacity for determination of internal pressure.
The diaphragm moves towards large or small open extent as a function of charging pressure. The pressure sensitive

Pressure

difference

sensor

5V power supply

Pressure difference signal

Earthing

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resistor is mounted on the diaphragm surface, of which the resistance varies under the application of pressure. These
resistors are connected to form a resistor bridge. Therefore, any movement of the diaphragm will change the balance
of resistor bridge, namely the voltage of the resistor bridge is one measurement of turbocharger pressure. The
evaluation circuit is functioned to amplify the bridge voltage and compensate the linear variation of temperature
influence and pressure characteristic. The output signal of evaluation circuit is transmitted to ECU and then the
turbocharger pressure is obtained by means of the programming characteristic curve.

The voltage drop on the resistor is inputted to the ECU via one analog and one digital converters (ADC), which is one
measurement for evaluating the temperature. The ECU micro-processor embodies one characteristic curve, which
defines the temperature as a function of given voltage.

3) Measurement analysis
Wiring terminals: 1 – Grounding, 2 – Temperature signal, 3 – +5V, 4 – Pressure signal.

4) Malfunction Mode

The light-up of the engine malfunction indicator lamp indicates the presence of malfunction in the engine system and
it’s necessary to diagnose with diagnosis instrument. Use Sunray special diagnosis instrument to communicate with
ECU of electronic injection system and read out the malfunction data in the ECU.

5) Troubleshooting

Use Sunray special diagnosis instrument to check the trouble code and determine whether there is short-circuit or
open-circuit between circuit of malfunction position and the grounding wire, whether there is short-circuit or
open-circuit to power supply, and whether the circuit is consistent with the given pin definition.

4. Thermal diaphragm air flowmeter

1) Overview

z The thermal diaphragm airflow sensor is one air mass sensor fitted with

logic output. To obtain the air flow, the sensor diaphragm on the sensor is
heated by the heating resistor installed in the middle and the temperature
distribution on the diaphragm is measured by the temperature resistors
installed paralleling with the heating resistor. The air flow passing through
the sensor changes the temperature distribution on the diaphragm to cause
resistance difference between two temperature resistors. The resistance
difference depends on the direction and flow rate of the airflow so that the
airflow sensor has high requirements over the flow rate and direction of the
airflow. The sensor manufactured by micro-machinery features small size,
low thermal capacity, and <15ms response time.

z The sensor is internally fitted with intake temperature sensor to measure the

intake temperature.

z The air flowmeter is installed at the port of the air cleaner.

z Wiring terminals: 1. +12V power supply; 2. Grounding; 3. Air temperature signal; 4. Airflow rate signal.

Turbocharger pressure

and temperature

sensor

Grounding

5V power supply

Intake pressure signal

Intake temperature signal