MINISTRY OF EDUCATION AND TRAINING HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION Ho Chi Minh City, May 2024 GRADUATION THESIS AUTOMOTIVE ENGINEERING TECHNOLOGY RESTORATION AND
INTRODUCTION
Reasons for choosing the topic
As Vietnam's automotive industry booms, the demand for skilled technicians surges To foster the next generation of professionals, our team embarks on a research project to restore and study the Common Rail D4CB Engine Model By providing hands-on experience with the Common Rail fuel system used in Diesel engines, this educational initiative will equip students with the practical knowledge essential for their future careers.
Research purposes
Understanding the structure and operation of a diesel engine using the Common Rail fuel system Restoring and researching the Hyundai Common Rail D4CB Engine Model to help reintegrate the model into the future engine teaching program.
Research subjects
Hyundai Common Rail D4CB Engine Model.
Research scope
The structure and principles of the systems on the Common Rail D4CB Engine Model We focus on researching the fuel system and control system on the Hyundai D4CB engine.
Research method
Using the method of researching relevant documents as well as based on the knowledge learned to restore the model to its normal operating state
COMMON RAIL SYSTEM THEORY
Overview the formation and development of the common rail system
With the continuous development of automotive technology, the requirements for fuel systems on engines are increasing Then the Common Rail Diesel (CRD) system was born
• 1916: Common rail injection was first applied in submarine engines by Vickers, the engines with the common rail fuel system were first used in the G-class submarines
• Late 1960s: Robert Huber, a Switzerland engineer, developed the prototype of the Common Rail system for automotive engines The technology was further developed by Dr Marco Ganser at the Swiss Federal Institute of Technology in Zurich
• 1990s: The modern version of the Common Rail injection system that is used in diesel engines was invented During this time, the German company Robert Bosch GmbH and the Denso Corporation from Japan both introduced the modern common rail injection system to automobiles
• 1995: The Denso Corporation obtained the concept from Renault and managed to implement it commercially
• Early 1990s: Mario Ricco was researching advancements for the CR injection system with the Fiat group When the Fiat group hit hard financial times, they sold the concept and research to Robert Bosch GmbH
• 1997: The first car equipped with the Common Rail system was manufactured, assembled, and introduced to the market
This system has significantly improved the efficiency and performance of diesel engines, and continues to be widely used in modern diesel engines today
Compared to the old cam-driven system, the Common Rail system is quite flexible in adapting to control fuel injection for diesel engines, such as:
• Wide range of applications: For cars and small trucks with power up to 30 kW/cylinder, as well as heavy trucks, trains, and ships with power up to 200 kW/cylinder
• Injection pressure can reach about 1600 - 1800 bar
• Injection pressure can change according to different engine operation stages
• Can change the timing of fuel injection
• Can inject in 3 stages: pilot injection, main injection, post injection.
Function of the system
The creation of pressure and fuel injection are completely separate in the Common Rail system The injection pressure is generated independently of the engine speed and the volume of fuel injected Fuel is stored at high pressure in the high-pressure accumulator and is ready to be injected The volume of fuel injected, the timing of injection, and the injection pressure are calculated by the ECU Then, the ECU controls the injectors at each engine cylinder to inject fuel.
Construction
Figure 2 1: Common rail system construction
According to [1], Fuel system in the common rail system include three main component groups:
• Low-pressure stage: Fuel tank, fuel filter, feed pump
• High-pressure stage: High pressure pump, suction control valve, rail, injector, rail pressure sensor, fuel limiter valve
• Electronic diesel control: ECU, sensors, actuators
The fuel filter in a diesel engine has the following main functions:
• Removes impurities: The fuel filter removes impurities from the fuel, cleaning it before it is introduced into the car engine
• Water separation: For Diesel engines, the fuel filter has an additional component to separate water from the fuel
• Engine protection: The fuel filter helps protect the engine from damage that impurities can cause
• Improves performance: Removing impurities helps improve the performance of the engine
Feed pump in this system is gear pump It is located inside of high-pressure pump and supplies fuel to high pressure pump In some system, an electric pre-supply pump can be used in a combination with feed pump
The function of the high-pressure pump is to create high pressure for the injection process Fuel from the feed pump is compressed with high pressure by the high-pressure
6 pump and fed into the fuel rail The type of pump used on the D4CB engine is the Bosch CP3 pump
High pressure pump CP3 is the radial-piston pump, the fuel-delivery is control through a metering unit (Suction Control Valve – SCV) The pump is located on the engine block, driven by the crankshaft pulley and lubricated by diesel fuel The main differences with the previous generations include monobloc housing and the changing in mechanical structure By that, the pump can operate at higher delivery rate and capable of withstanding the pressure up to 1800 bar
Figure 2 6: High-pressure pump cross-section
The pump uses 3 plungers arranged radially, placed 120 degrees apart and operating alternately in one rotation of the pump shaft Therefore, the stress on the drive system remains synchronized There is also less pressure on the drive system, and thus the power required to drive the pump is reduced, according to [1]
Figure 2 7: High-pressure pump operation
The feed pump extracts fuel from the tank and transports it to the inlet of the SCV The opening of the SCV determines the fuel volume entering the pump chamber As the plunger descends, fuel flows into the pump's chamber Subsequently, the eccentric cam drives the plunger upwards, compressing the fuel Pressurization continues until it exceeds the rail's high-pressure force and spring force, enabling the fuel's entry into the rail This process repeats sequentially with three plungers.
Suction control valve (SCV) is the most important part of the common rail system
It is attached on the fuel inlet position of the high-pressure pump It ensures that the pump delivers exactly the right quantity of fuel to the fuel rail in order to maintain the injection pressure required by the system
Figure 2 9: Suction control valve construction
Figure 2 10: Suction control valve operation
The SCV receives fuel from feed pump and supplies it to the high-pressure pump Depending on the different operating modes of the engine, the rail requires different
9 pressures The rail pressure sensor will read this value and send it back to the ECU, which will adjust the opening of the metering valve accordingly through PWM signal For example:
When the pressure in the rail exceeds the required value, the ECU will control the valve to reduce the opening and decrease the amount of fuel fed into the rail
When rail pressure falls below the desired value, the ECU intervenes to adjust the valve, increasing its opening to facilitate a rapid pressure increase.
The control signal of SCV is negatively triggered PWM from ECU with the operationg frequency about 180Hz
Figure 2 11: SCV signal at idle speed
Figure 2 12: SCV signal at 4500 rpm
In [2], When engine at idle speed (about 800 rpm), close duty is about 45%, which limits the fuel flow into pump chamber
10 When engine run at high speed (4500 rpm), at this time rail pressure is 1350 bar The ECU controls the SCV to reduce close duty to 35%, which increases fuel flow to the pump chamber
2.3.2.3 High-pressure accumulator (Common rail)
High-pressure accumulator stores the high-pressure fuel and distributes to the injectors Its main duty is reducing the pressure fluctuations created by high pressure pump and when the nozzles open The rail volume must be large enough to dampen the fluctuations and small enough to start engine faster Typical volume of fuel in common rail is 16 – 20 cm 3 , according to [4]
This high-pressure accumulator is common to all cylinders Therefore, its name is
"common rail" Even if some fuel is lost during injection, the rail maintains the actual internal pressure constant The pressure change is due to the high-pressure pump changing the amount of fuel supplied to compensate for the fuel just injected
The pressure limiter valve functions as a safety valve In case the pressure exceeds a high level, the plunger is pushed by the pressure in the rail against the spring force Then the fuel goes through the fuel return line and the rail pressure drops The pressure limiter allows the maximum instantaneous pressure in the pipe to be about 1750 bar, according to [4]
At normal operating pressure (up to 1350 bar), the spring pushes the piston down to seal the pipe When the system pressure exceeds the level, the piston is pushed up due to the oil pressure in the pipe overcoming the spring tension The high-pressure fuel is released through the valve and enters the fuel return line back to the tank When the valve opens, the fuel leaves the pipe, so the pressure in the pipe decreases
Injectors are the final output of the common rail system, responsible for injecting fuel into the combustion chamber to generate power
The operation of the injector can be divided into three main phases:
Injector closes (Non injection phase): The injector needle is in the closed position Under the pressure of valve spring, the valve ball is pushed down and closes the outlet orifice Pressure at two sides of plunger is balanced
Figure 2 15: Injector solenoid type construction
HYUNDAI COMMON RAIL D4CB ENGINE MODEL
Engine specification and application on vehicle
Table 3 1: Hyundai D4CB engine specification
352 Nm at 2000 rpm Valve timing
Flatness of gasket surface 0.15 mm
Oil quantity (Drain and refill including oil filter)
Above API CF-4 or ACEA B4 Cooling method
Cooling system Forced circulation with cooling fan
Type of high-pressure pump
Common Rail Diesel Bosch CP3
Exhaust gas regulation system (EGR)
17 The Hyundai A engine, also known as the D4CB, is a 2.5-liter inline 4-cylinder diesel engine produced by the Hyundai Group since 2002 The engine was entirely designed and manufactured by Hyundai
The engine uses dual overhead camshafts with a total of 16 valves and the second- generation common rail fuel system from Bosch along with direct injection The exhaust gas regulation system is also implemented, helping the engine meet the Euro 3 standard
The models that use this type of engine are the Hyundai Starex, Hyundai Porter, Kia Sorento, and Kia Bongo
Electronic control unit (ECU)
3.2.1 Function of ECU in a diesel engine
In a diesel engine, the ECU controls the fuel injection process, ensuring the right amount of fuel is injected into the combustion chamber at the right time This precise control helps in achieving better fuel efficiency and reduced emissions
The ECU (Engine Control Unit) includes microprocessors, memory chips, signal converters, and output pins From there, the ECU collects and processes signals input from various sensors, then controls the actuators based on the data received Each engine will have different maps suitable for its operation, which are stored in the ECU's memory
Figure 3 5: Input and output signal of ECM
16 EGR valve control signal EGR
20 To main condenser fan relay FAN
54 Brake position switch BRAKE CRUISE
58 IG ON/OFF signal IGSW
76 Acceleration pedal sensor ground 1 EPA
77 Acceleration pedal sensor signal 1 VPA
78 Acceleration pedal sensor supply 1 VCPA
79 Acceleration pedal sensor ground 2 EPA2
80 Acceleration pedal sensor signal 2 VPA2
81 Acceleration pedal sensor supply 2 VCPA2
1 Fuel temperature sensor signal THF
2 Fuel temperature sensor ground ETHF
3 Water temperature sensor signal THW
4 Water temperature sensor ground ETHW
5 Intake air temperature sensor signal THA
7 Air flow sensor ground VG
8 Air flow sensor signal VC
10 Rail pressure sensor signal PCR
11 Rail pressure sensor ground EPCR
16 Air flow sensor supply Air flow sensor supply
17 Crankshaft position sensor signal (+) Ne+
18 Crankshaft position sensor signal (-) Ne-
20 Crankshaft position sensor shield SHIELD
27 Metering valve (SCV) high side SCV+
28 Metering valve (SCV) low side SCV-
30 Glow time indicator lamp GIND
36 Injector bank for cylinder No.1 and No.4 COM 1+4
37 Injector bank for cylinder No.2 and No.3 COM 2+3
Figure 3 7: Electric wiring diagram of Hyundai D4CB engine
Figure 3 8: Electric wiring diagram of Hyundai D4CB engine
Figure 3 9: Electric wiring diagram of Hyundai D4CB engine
Figure 3 10: Electric wiring diagram of Hyundai D4CB engine
Engine sensors
Figure 3 11: Accelerator position sensor location
Linear sensors (resistance value changing) are used Linear sensors use a variable resistor to record the position and direction of movement of a mechanical part to report to the computer Linear sensors have 3 connecting wires The third end is a signal that freely slides on the resistor, when the signal wire slides freely on the resistor, the voltage will change
Figure 3 12: Accelerator position sensor circuit and signal
Figure 3 13: Accelerator position sensor wiring diagram and connector
Table 3 4: Accelerator position sensor voltage test
3.3.2 Mass air flow sensor (MAF) and Intake air temperature sensor (IAT)
Figure 3 14: MAF sensor and IAT sensor location
The intake air temperature sensor is integrated with mass air flow sensor in the air flow meter
This is a hot wire type sensor It uses a hot wire placed on the air path and an electronic control circuit
2-5 Press pedal to maximum position 0.625 – 3.95 volts 3-6 Press pedal to maximum position 0.37 – 1.95 volts
Figure 3 15: Mass air flow sensor construction
The hot wire is a PTC (Positive Temperature Coefficient) sensor When the temperature increases, the sensor resistor increases according to it It is powered by battery voltage and its temperature rises up and stay constant at 120 o C When the intake air passes through the hot wire, it cools the hot wire, the resistance of the hot wire decreases, and the additional current needed to maintain the temperature of the hot wire increases This additional current is used to signal the ECU about the mass of intake air The ECU recognizes this signal and uses it to calculate the injection volume according to the air inlet
Figure 3 17: Intake air temperature sensor wiring diagram
The intake air temperature sensor is integrated with the MAF sensor It uses a negative temperature coefficient (NTC) When the temperature increases, the sensor resistance decreases The sensor is powers 5 volts from ECU, and be in series with a resistor
R, when the temperature changes, the sensor resistance changes in according It makes the voltage from THA terminal change, ECU uses this signal to control the fuel injection
Figure 3 18: Air flow sensor connection
Table 3 5: Air flow sensor voltage test
Figure 3 19: Crankshaft position sensor location
The crankshaft position sensor used is a type of induction, the important parts of this sensor are: induction coil, magnet, and notches on flywheel
When the notch moves away from the magnetic pole, the magnetic field in the induction coil change The reason for the changing of the magnetic field is that the air gap
1 & 3 Engine run at idle speed 1,6 volts
34 has a large magnetic resistance, when the notch moves closer to the magnetic pole, the air gap decreases and the magnetic field concentrates through the coil When the magnetic field passes through the coil, the force lines will induce an alternative current in the coil This change in current is used to determine the position of the crankshaft, providing crucial information for engine timing and fuel injection systems
Figure 3 21: Crank shaft position sensor wiring diagram and connector
Quick test method: Use an LED light and connect its two poles to the Ne- and Ne+ poles, then start the engine If the light flashes, the sensor is still working well
For more accuracy, use oscilloscope to measure the waveform The correct waveform is shown below:
Figure 3 22: Crankshaft position sensor signal (below)
Figure 3 23: Camshaft position sensor location
Figure 3 24: Hall effect type sensor construction
The function of the camshaft position sensor is to determine the top dead center of cylinder number 1 and the position of the camshaft to adjust the precise injection timing
Operation: There is a metal notch on the camshaft, which rotates as the camshaft rotates The camshaft position sensor is installed facing this notch When the notch sweeps past the sensor head, the gap between the sensor head and the notch changes, the ICs in the sensor will generate a signal pulse sent to the ECU, and from there the ECU recognizes the top dead center of cylinder number 1
Figure 3 25: Camshaft position sensor wiring diagram and connector
Table 3 6: Camshaft position sensor test
Figure 3 26: Camshaft position sensor signal (above)
Figure 3 27: Rail pressure sensor location
Figure 3 28 Rail pressure sensor construction
3 Steel diaphragm with deformation resistors
The fuel pressure sensor plays a crucial role in modern fuel injection systems It monitors the fuel pressure in the high-pressure pipe and sends this information to the Engine Control Unit (ECU) with high accuracy and speed Operating on the principle of measuring instantaneous pressure, the sensor ensures optimal fuel system performance by providing real-time data to the ECU for fuel injection and engine management.
When the diaphragm deforms, the resistance layer placed on the diaphragm will change its value The deformation is due to the pressure increase in the system, the change in resistance causes a change in the voltage of the circuit
Figure 3 29: Rail pressure sensor wiring diagram
Figure 3 30: Rail pressure sensor characteristic
The voltage changes about 0 - 70mV (depending on the applied pressure) and is amplified by the amplifier circuit to 0.5 - 4.5V The signal is used by ECU to determine the rail pressure and then calculate the % duty cycle applied to the metering valve solenoid
Table 3 7: Rail pressure sensor voltage test
3.3.6 Engine coolant temperature sensor (ECT)
Figure 3 31: Engine coolant temperature sensor location
Engine coolant temperature sensor is mounted on the cylinder head, contact directly with the coolant
Figure 3 32: Engine coolant temperature sensor wiring diagram
The sensor is used to determine the temperature of the engine coolant The sensor structure includes a semiconductor with a Negative Temperature Coefficient (NTC) similar to intake air temperature sensor When the sensor temperature is low, the sensor resistance is high The change in resistance will affect the electrical signal sent to the ECU The semiconductor thermistor is supplied with a stable voltage (5 volts) The sensor is connected in series with the resistor R in the ECU When the resistance value of the sensor
40 changes, the voltage at the THW pin also changes accordingly Based on that signal, the ECU calculates the injection volume
The adjustment temperature of the ECT sensor is 80 o C, if the sensor is broken, the engine will use 80 o C to control the injection Signal is also sent to the ECT gauge in the instrument cluster, so that driver can know the engine temperature to avoid overheat problem
Figure 3 33: Engine coolant temperature sensor connector
Table 3 8: Engine coolant temperature sensor resistance test
Figure 3 34: Fuel temperature sensor location
The fuel temperature sensor shares similarities in structure and operation with the engine coolant temperature sensor and intake air pressure sensor Its primary function is to measure fuel temperature, which enables the fuel injection system to adjust the amount of fuel injected based on the temperature of the fuel This adjustment ensures optimal fuel efficiency and engine performance.
Figure 3 35: Fuel temperature wiring diagram
Because of the same structure, fuel temperature sensor also has the same testing method to the ECT sensor
Engine actuators
To calculate the optimal volume of fuel injection, the ECU must calculate the basic fuel injection volume and the maximum fuel injection volume It then compares these two parameters and uses the smaller one Next, it adjusts this injection volume to produce the optimal injection volume to deliver to the injector
Figure 3 36: Injection volume control diagram
Figure 3 37: Basic injection volume control diagram
The basic fuel injection volume is determined by the engine speed (Ne) and pedal position When the engine speed is constant, increasing the throttle angle will increase the fuel injection volume
Maximum Fuel Injection Volume control:
The maximum fuel injection volume is based on the crankshaft position sensor and other sensors such as the engine coolant temperature sensor, intake air pressure sensor, fuel temperature sensor, etc
Figure 3 38: Maximum injection volume control diagram
ECU compares the basic injection volume and the maximum injection volume, then the smaller will be chosen to control the injectors
The fuel injection volume on starting:
The fuel injection volume on starting bases on the coolant temperature and engine speed When the ignition switch turns to start position, start quantity signals are generated until the required minimum engine speed is reached
Figure 3 39: Injection timing control diagram
The Engine Control Unit (ECU) determines the base injection timing based on engine speed and total injection volume It then modifies the timing of the pilot and main injection events using input from sensors monitoring air flow, intake air temperature, and coolant temperature to optimize the engine's performance.
Pilot injection occurs before top dead center (BTDC) The injector is adjusted to spray a small amount of fuel (1-4 cc) into the cylinder This injection process can help the engine achieve several efficiencies It increases the end-of-compression pressure, due to the combustion of the pilot fuel This reduces the sudden increase in combustion pressure when the main injection is performed This helps the combustion process to occur more smoothly and reduces the ignition delay This also reduces engine noise, reduces fuel consumption, and improves emissions
Figure 3 41: Relation between injection and combustion pressure
The main injection helps generate power for the engine, and can also be divided into multiple stages
The purpose of post-injection in a common rail system is to reduce particulate emissions This is achieved by injecting a small amount of fuel shortly after the main injection This improves the mixing of fuel and air during a late phase of combustion, which increases temperatures in the combustion chamber and promotes soot oxidation In other words, the ignition of the fuel injected during the post-injection cycle helps burn off the last unburned diesel droplets of the main injection This process controls emissions and contributes to a cleaner and more efficient combustion process
Figure 3 42: Idle-speed control diagram
Its function is to maintain the engine speed at a specific level when there is no input to the accelerator pedal to prevent the engine from stalling Depending on the operation of the engine, this speed can change, for example, when the air conditioning switch is turned on, the engine has to pull the compressor, so the controller has to increase the idle speed to prevent the engine from stalling In addition, to reduce the amount of exhaust emissions into the environment, the idle speed must be at the lowest possible level
Figure 3 44: Glow system wiring diagram
The glow system is designed to enhance the engine's starting capability and minimize smoke during cold starts In this system, if the coolant temperature is below 60°C, the ECU does not establish a connection between the mass and pole 18 When the ignition switch is turned to the ON position, the glow indicator light comes on Simultaneously, the connection of the mass to the glow relay is controlled, providing current to the glow plugs for rapid heating The resistance of the glow plug is relatively
The glow plugs, essential for diesel engines, begin heating when the ignition key is turned, reaching a temperature of approximately 800°C within 3.5 seconds After a brief cool-down period, the glow indicator light extinguishes, indicating engine readiness Upon engine start, the glow plug controller automatically disconnects the glow relay after 18 seconds of operation.
When the coolant temperature exceeds 60°C, the thermal switch moves to the ON position, and the glow indicator light turns off after 0.3 seconds
The glow plug has the task of heating the air in the combustion chamber to enhance the combustion efficiency of the fuel
To check glow plug for damage, a VOM is used in continuity test mode Connect two poles of VOM to terminal and body of glow plug If the VOM beeps or the resistance displayed is 1.8 Ohm, the glow plug is still usable If the resistance displayed is too high, replace the glow plug
Figure 3 45: Glow plug testing method
3.4.4 Exhaust gas regulation valve (EGR)
Figure 3 47: EGR vacuum type operation
The goal of the EGR system is to reduce the concentration of Nitrogen Oxides (NOx) by recirculating exhaust gases back into the engine intake system under load conditions
49 The effect of this exhaust gas is to reduce the combustion temperature or reduce the oxygen goes to cylinder In addition, the recirculated exhaust gas also increases the specific heat of the air-fuel mixture, so the combustion temperature decreases The goal of lowering these parameters is to prevent the formation of NOx, which can be formed in high temperature (above 1300 o C) in the combustion chamber
When the combustion chamber temperature is high, the EGR will allow a small volume of exhaust gas into the mixture with air and fuel However, this amount of exhaust gas must be controlled and adjusted appropriately Because if a large amount of exhaust gas goes into the combustion chamber, the engine will operate unstably, affecting the engine power Due to the influence of the above reason, the amount of exhaust gas is controlled by the EGR valve, and the amount of exhaust gas introduced into the engine depends on two basic parameters: engine speed and engine load
The turbocharger enhances engine power by compressing air into the combustion chambers, functioning on exhaust gas It comprises two components connected by a shaft: the turbine, attached to the exhaust manifold, and the compressor, connected to the intake manifold.
The turbocharger is mounted directly at the engine exhaust port to take advantage of the exhaust gas flow to rotate the exhaust turbine, the compressor will rotate accordingly and compress clean air passed through the intake into the combustion chamber again
RESTORATION
Engine initial condition
Initial condition: The engine was disassembled the timing chain
Figure 4 1: Engine initial condition (Top view)
Figure 4 2: Engine initial condition (Front view)
At the time we received the model, the timing system and high-pressure pump was disassembled Some parts were lost
53 Three glow plugs were broken
Fuel filter was too old
Processing on restoration
Firstly, we check for the parts and start to assemble the timing system by following steps in the repair manual
Figure 4 5: Hyundai D4CB repair manual
Following the steps in the book, we must make sure that the marks are in right position
Figure 4 10: Correction timing marks (camshaft gear)
Figure 4 11: Correction timing mark (High-pressure pump gear)
After assemble the timing system, we start the engine but the engine does not work: The starter work but the engine still not run
4.2.2.1 Camshaft position sensor and crankshaft position sensor
• Then use a LED and connect to G+ and G- terminals
• Start the engine and observe the LED
The voltage is 5 volts, start the engine, the LED flashes, so the CMP sensor is still working But we need the accurate result, the oscilloscope is used to measure the waveform
Check wire harness (Camshaft position sensor - ECM):
• Disconnect the CMP sensor connector
60 Measure the resistance of the wire harness side connectors:
Table 4 1: Camshaft position sensor wire side resistance test
C230-2-22 or C205-2 (G+) - Mass 5 kΩ or higher C230-2-23 or C205-3 (G-) - Mass 10 kΩ or higher
After measuring the resistance of the wire harness, we see that the values are in allowable range.
Inspect Crankshaft Position Sensor (Resistance):
• Use a LED and connect to G+ and G- terminals
• Start the engine and observe the LED
When we start the engine, the LED flashes, so the LED still work
Check wire harness (Crankshaft position sensor - ECM):
• Disconnect the CKP sensor connector.
Measure the resistance of the wire harness side connectors:
Table 4 2: Crankshaft position sensor wire side resistance test
C230-2-18 or C213-3 (Ne+) - Mass 10 kΩ or higher
61 C230-2-19 or C213-2 (Ne-) - Mass 10 kΩ or higher
After checking the resistance of the wire harness side connectors We found that the parameters of the sensor are still in the allowable range
After LED tests and resistance tests, we use oscilloscope to measure the waveform of CMP and CKP sensor.
The standard waveform of CKP and CMP sensor as shown below:
Figure 4 13: CKP and CMP reference waveform
Figure 4 14: CKP and CMP measured waveform
After measuring the CMP and CKP sensor waveform, we found that the sensor is still working normally.
Because of being used for many years, the filter needed to be changed We replaced the oil filter with a new one to ensure the engine operates most efficiently
Check high pressure pump (Metering valve):
• Disconnect the metering valve connector.
• Measure the resistance of the valve.
1-2 (Standard parameter) 1.9 to 2.3 Ohm at 20°C 1-2 (Measure parameter) 3.0 Ohm
We found that the result matching with the standard value
• Measure the resistance of the wire side connectors.
Table 4 4: SCV wire side resistance standard parameters
C230-2-27 or C214-1 (SCV+) - Mass 10 kΩ or higher
C230-2-28 or C214-2 (SCV-) - Mass 10 kΩ or higher
After checking the resistance of the wire harness side connectors We found that the parameters of the valve are in the allowable range
Continue to check the waveform:
Figure 4 16: SCV control waveform measured Engine stationary (left side) and engine cranking (right side)
After checking waveform, we knew that SCV was still in good condition because the close duty % decrease when starting engine
We tested for the resistance and injection volume of the injectors:
For the injector solenoid test, the procedure:
• Measure the resistance between two terminals on the injector
The reference resistance: 0.310 – 0.420 Ω, according to [5]
Figure 4 18: Injector solenoid test (injector No.1 to No.4)
After the test, all the injector solenoids were good
For the resistance test for wire side connector, the steps:
• Remove the injector side connectors, remove ECU side connectors
• Use VOM in resistance measure mode
65 The standard parameters are shown below:
Table 4 5: Injector wire side resistance standard parameters
After the test, the injector was good
Before starting the volume test, the injectors needed to be removed The removal procedure:
• Remove the high-pressure pipe and the return line
• Take the injector out of cylinder head
To test the injector volume, a common rail test band was used
Figure 4 20: Common rail test bench
• Connect the test band to power source and compressed air line
• Insert the injector to the test band
• Press Up/Down button to ensure the tightness between the injector and the test band
• Press Power button → Low motor → High motor → Low
• Base on the injector code Adjust the parameters by the adjustment knob similar to test table
• Then press Start button to run, wait for the machine to finish
• Record the injection volume and returned volume
• Do the same job with Medium, High, Pilot mode
• Compare to the standard parameters
The injector codes of this engine were 092
Figure 4 21: Injector test parameters Table 4 6: Injector code 092 test parameters
Table 4 7: Injection volume tested result
68 The result shown that injector number 4 was broken, the others generally near the standard
Then we went to the diesel shop to repair the broken injector
Figure 4 22: Injector test at diesel shop
Figure 4 23: Repair the broken injector
After the repair, the injector was back in operation We reinstalled the injectors to the engine
Checking for voltage of the sensor terminal
Table 4 8: Rail pressure sensor standard parameters
1 (VPCR) – 3 (EPCR) IGSW ON 5 volts
2 (PCR) – 3 (EPCR) IGSW ON 0.5 volts
2 (PCR) – 3 (EPCR) Engine cranking 0.5 → 1.3 volts +
After measure voltage follow the default parameter, we found that when engine cranking, the voltage of PCR terminal stays constant at 0.5 volts This means that fuel is not delivering to the rail So we start to check the high-pressure pump
Figure 4 24: Rail pressure signal measured
The function of high-pressure pump is raising the fuel pressure and delivering to high- pressure accumulator (rail) It is driven by the crankshaft pulley
When we switch the IGSW to start position, the starting motor works normally Then we take out the high-pressure line of the pump and observe the fuel after passing the high-pressure pump We found that the fuel line is very weak
Figure 4 25: High-pressure pump outlet bad fuel flowrate
To the engine cranking, the fuel pressure must reach 300 – 400 bar, according to 1.3 volts of PCR signal
Then, we took the pump out of the engine and brought it to the common rail repair store After a common rail test, the pump still worked normally
Figure 4 26: High-pressure pump test
However, after reinstalling the pump to the engine, the pressure still was not change Then, we noticed on the connecting between the high-pressure pump and its drive gear It is not using the key although there is a key seat on the pump drive shaft In some
The key on the pump gear in traditional engines serves to orient and hold the gear in place However, in this particular pump, a clamping force between two conical surfaces is utilized to secure the gear After thorough inspection, it was discovered that the bolt's thread surface on the pump drive shaft exhibited signs of damage During the tightening of the nut, thread stripping occurred, preventing the two components from being adequately clamped together Consequently, as the engine rotates, the pump gear and pump shaft slip, resulting in the high-pressure pump's inability to compress high-pressure fuel to the desired level.
After that, we installed a new pump and repeated the measurement process
Using VOM at DC voltage test mode to measure voltage between PCR and EPCR terminals
Table 4 9: Rail pressure sensor measured voltage
2 (PCR) – 3 (EPCR) IGSW ON 0.5 volts
2 (PCR) – 3 (EPCR) Engine cranking 1.3 volts
Figure 4 28: Rail pressure signal measured (new pump)
The Vehicle Operation Monitor (VOM) inspection indicated sufficient fuel pressure, and the engine displayed signs of attempted ignition After prolonged cranking, the engine successfully started.
After the engine run, we checked for the idling The engine had a lot of smoke coming from breather pipe We also found the engine oil leaked from turbocharge The engine performed a bad power All the problems of the engine were:
Hard starting could come from:
In the causes above, only compression pressure was not tested So we moved to the test
Because of the different structure of the test tool We processed the test from glow plug holes instead of injector holes
• Remove all the glow plugs
• Use a inspection tool with appropriate connector for the glow plug hole
• Tighten the tool to the hole
• Connect the pressure gauge to the tool
• Start the engine for 5 second and record the gauge value
• Then fill a small amount of oil to the hole, which called wet test, then start the engine and record value
• Do the same job to 4 cylinders
• Compare to the standard value
Table 4 10: Compression pressure measured result
Standard pressure (in kg/cm 2 ) 30 30 30 30
Compression pressure wet test (in kg/cm 2 ) 19 20 20 22
The pressure value was too low compare to the standard value, the wet test is to determine piston ring leakage Observing the result, some problems could be:
The engine needed to have an overhaul to inspect and replace the damage parts
4.2.3.2 Smoke from crankcase vent hose
Figure 4 29: Smoke from crankcase vent hose
The vent hose serves to ventilate the crankcase with the outside environment When the engine operates, gas can form in the crankcase through the compression process as well as the rotation of the crankshaft, causing the pressure in the crankcase to rise If this amount of gas is not vented to the outside, it can cause oil leakage, damage to oil seals, gaskets, and many other problems
When the engine ran, there was a lot of smoke from this hose The causes of this problem can be from piston ring damage The piston rings wear made the air in the compression stroke leaked to the crankcase and move out through the vent hose Engine overhaul was essential
Figure 4 30: Oil leaked from turbocharger
75 Oil entered the turbocharger to lubricate the connecting shaft between the compressor and the turbine The cause could be oil sealing rings damage Then we brought the turbocharger for restoration
With the permission and support from the department, we have undertaken an engine overhaul to inspect and repair the damaged parts
The process followed the repair manual Before removing cylinder head, the relative parts needed to be removed
• Then, cylinder head was removed
Figure 4 34: Cylinder head assembly (above)
Figure 4 35: Cylinder head assembly (below)
• After removing camshafts, marked the cam follow according to position
After remove the cylinder head, we found that a lot of oil in the piston heads of cylinder #1 and #2
• Fill the contact surface between the valve face and valve seat with diesel oil
• Use high-pressure air (about 6 kg/cm 2 ) to spray into the valves from the intake and exhaust of the cylinder head
• If diesel oil bubbles at any valve, that valve is leaking
The result of valve leakage test shown that all valves were leaked We needed to resurface the valve
Figure 4 39: Grinding paste and valve removing SST
Resurfacing the valves or grinding is the action of renewing the contact surface between the valve face and valve seat, helping to seal it
Here are the steps to perform it:
• Use SST to remove the retainer lock, valve retainer, and valve spring from the valve
• Use valve grinding paste, this jar has two ends, one end is coarse paste and the other end is fine paste
• Apply a thin layer of coarse paste onto the valve surface, then apply an additional layer of oil
• Use a soft plastic tube to connect to the valve stem
• Use your hand or a machine to rotate the tube 360 degrees and move it up and down so that the paste can get into the contact surface and to better friction between the two surfaces
• After the coarse paste has smoothed, remove the valve and clean the contact areas
• Repeat the same steps with fine paste and finally oil to polish the surface
• Install the valve and related details back into the cylinder head
• Proceed to test the tightness at the resurfaced valve If there is still leakage, repeat the steps from the beginning
Figure 4 40: Damage valve head contact surface
Figure 4 41: Damage valve seat surface
Figure 4 42: Valve head and valve seat after resurfacing
After doing resurface job, we retest for valve leakage and there was an improvement Most of the valves were in good contact
Valve stem seals play a crucial role in preventing engine oil from seeping into the combustion chamber Their function is to maintain a tight seal around the valve stems, preventing oil from entering the chamber during the engine's operation This is particularly important after the valve grinding process, as the removal of material from the valves during grinding can affect the seal's effectiveness Replacing the valve stem seals ensures proper engine operation by preventing oil contamination and maintaining optimal performance.
Figure 4 43: Remove the old stem seal and install the new ones
Then, the cylinder head flatness was checked The reference distortion: 0.15 mm The inspection shown that the flatness met the requirement
Figure 4 44: Measure cylinder head distortion
The steps to clean the lubrication system:
• Use diesel oil to clean the oil pan
• Use compressed air spray to engine oil line, remember to cover the gun with a towel to ensure the oil does not splash and stain your clothes
• After ensuring the line ventilation, apply sealant to oil pan contact surface and install it to the engine block
• Replace the oil filter with the new one
Figure 4 45: Using compressed air to clean lubrication system
After all the repair, the cylinder head was installed to the engine block The procedure followed the repair manual The process is shown below:
• Install a new cylinder head gasket:
Figure 4 47: Cylinder head gasket installed
• Install the cylinder head and tighten the bolts The tightening torque and tightening order were followed the repair manual
Figure 4 48: Cylinder head bolt tightening torque and order
• After installing cylinder head, the hydraulic lash adjuster (HLA), rocker arm, cam carrier, camshaft and caps were installed respectively
Figure 4 50: HLA, rocker arms and cam carrier installation
Figure 4 51: Camshaft caps tightening torque
Figure 4 52: Cylinder head assembly installed
• Then, the cylinder head cover gasket was also replaced to ensure the tightness Its tightening order and torque are shown below:
Figure 4 53:Cylinder head cover tightening torque and order
Figure 4 54: Cylinder head cover gasket replacement
After a long time working, the EGR valve was full of carbon deposit Cleaning the valve helped it operate more smoothly
Figure 4 55: EGR valve before cleaning
Figure 4 56: EGR valve after cleaning
Figure 4 57: EGR valve after cleaning (inside)
The order parts of the engine were installed
91 The old lubrication oil was replaced
Oil quantity (Drain and refill including oil filter)
9.0L 7.4L 8.2L Above API-CF4 or ACEA B4
Following the standard parameter for the normal operation of the engine We chose the oil had the quality CI-4
Figure 4 59: Diesel engine lubrication oil
After finishing the installation, we connected the engine to battery and check for signals When all the sensors were ready, we started the engine At this time the engine was in good operation, the power was increased There was no smoke from the exhaust pipe anymore The project was completed
Table 4 12: Replaced parts of the engine
4.3.3 Some pictures of the model
Figure 4 62: Model from front view
Figure 4 63: Model from right view
Figure 4 64: Model from rear view
Figure 4 65: Model from left view
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
After a period of time working on our graduation project, our team has completed the topic 'Restoration and Research of Hyundai D4CB engine model' Throughout the process of implementing the project, we have accumulated a lot of in-depth knowledge about Diesel engines, especially the Common Rail system This has helped the team members to gain confidence for their future journey
The following are some of the group's accomplishments:
➢ Established a theoretical basis for the restoration and research of the Hyundai Common Rail D4CB engine model
➢ Repaired and replaced the damaged parts of the model
➢ Conducted a thorough overhaul to restore the original performance of the model
➢ The model, after being repaired, can continue to be used for the teaching work of lecturers, as well as for the practice on the model by future students.
Recommendations
The model still has imperfections It is hoped that in the future, the model will be improved to be closer to reality, serving better for teaching and learning purposes
We hope upcoming cohorts will tackle even more captivating and practical projects Our deepest gratitude to Mr Dinh Tan Ngoc for his invaluable contributions We also acknowledge the unwavering support of the Faculty of Vehicle and Energy Engineering and the Faculty of International Education in providing the essential resources for our successful project completion.
[1] Konrad Reif Editor – Diesel engine management, system and components – Bosch Professional Automotive Information, 2014
[2] A–2.5TCI Common rail diesel direct injection – Kia Motors https://dokumen.tips/documents/kia-sorento-d4cb.html?pageF
[3] Hyundai D4CB 2.5L CRDi Repair and Service Manual
[4] https://www.slideshare.net/amgadradhihadi/common-rail-diesel-fuel-systems
[5] Electrical testing of Bosch common rail Injectors – Bosch https://www.ignetwork.co.uk/wp-content/uploads/2021/08/Bosch-common-rail- injectors.pdf