Diesel Engine Troubleshooting

DPF System (Diesel Particulate Filter)

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This system reduces emissions of PM (particulate matter). In order to collect PM, a DPF cleaner with built-in catalytic filter is mounted on the center pipe. The collected PM is handled with combustion processing during operation

pic1 118 DPF System (Diesel Particulate Filter)

Exhaust Gas Temperature Sensor
• The exhaust gas temperature sensor is installed to the front and rear of the DPF to detect the temperature in these positions. The engine ECU controls the exhaust temperature for PM combustion based on the signals from this sensor. The sensor element is a thermistor.

pic1 119 DPF System (Diesel Particulate Filter)

Differential Pressure Sensor
• The differential pressure sensor detects the difference in pressure at the front and rear of the DPF, and outputs a signal to the engine ECU. The sensor portion is a semiconductor type pressure sensor that utilizes the piezoelectric effect through a silicon element, and amplifies and outputs the voltage with its IC circuit. When PM is collected and accumulated in the DPF, the filter clogs and the difference in pressure at the front and rear of the DPF increases. Therefore, based on the signals from this sensor, the engine ECU judges whether or not to subject PM to combustion processing.

pic1 120 DPF System (Diesel Particulate Filter)

By optimizing the injection pattern and controlling the exhaust gas temperature based on the exhaust gas temperature and the difference in pressure at the front and rear of the DPF, PM is collected, oxidized, and self-combusted. When the exhaust temperature is low, adding after-injection after the main injection raises the exhaust gas temperature to approximately 250?C and promotes oxidation of the PM. When the PM is collected and accumulated, the post-injection is added and HC is added to the catalyst to raise the catalyst temperature to 600?C, which is the self-combustion temperature for PM. This combusts the accumulated PM in a short time. The engine ECU controls the A, B, and C times and the injection times.

pic1 121 DPF System (Diesel Particulate Filter)

Written by Jack

March 11th, 2019 at 6:25 am

Exhaust Gas Control System

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The exhaust gas control system is provided to improve warm-up and heater performance. This system actuates the exhaust gas control valve VSV, which is attached to the exhaust manifold. It increases the exhaust pressure to increase the exhaust temperature and engine load, in order to improve warm-up and heater performance.

pic1 116 Exhaust Gas Control System

The exhaust gas control system operates when the warm-up switch is ON, and all the conditions listed below have been met.

Operation Conditions
– The EGR is operating.
– The coolant temperature is below 70°C.
– The ambient temperature is below 5°C.
– A minimum of 10 seconds have elapsed after starting the engine.
– The engine speed and fuel injection quantity are in the state shown in the graph below.

pic1 117 Exhaust Gas Control System

Written by Jack

March 11th, 2019 at 6:15 am

Electronically Controlled Throttle

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The electronically controlled throttle is located upstream of the EGR valve in the intake manifold. It controls the throttle valve at an optimal angle to regulate the EGR gas and reduce noise and harmful exhaust gases.

• Signals from the engine ECU actuate the stepping motor, which regulates the throttle valve opening.
EGR Control
• To further increase the EGR volume when the EGR valve is fully open, the vacuum in the intake manifold can be increased by reducing the throttle valve opening, which restricts the flow of the intake air.
Noise and Exhaust Gas Reduction
• When the engine is being started, the throttle valve opens fully to reduce the emissions of white and black smoke.
• When the engine is being stopped, the throttle valve closes fully to reduce vibration and noise.
• During normal driving, the throttle valve opening is controlled in accordance with the engine conditions, coolant temperature, and atmospheric pressure.

pic1 115 Electronically Controlled Throttle

Written by Jack

March 11th, 2019 at 5:45 am

E-EGR System Operation

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• After the vacuum pump generates a vacuum, the E-VRV (electric-vacuum regulation valve) regulates the vacuum and
directs it to the diaphragm chamber of the EGR valve. In response to this vacuum, the diaphragm pushes the spring
downward, which determines the opening of the EGR valve and controls the EGR volume.
• The EGR cooler, which is provided in the EGR passage between the cylinder head and the intake passage, cools the
EGR in order to increase the EGR volume.
• The EGR cutoff VSV, which opens the diaphragm chamber to the atmosphere when the EGR valve is closed, helps
to improve response.

pic1 113 E EGR System Operation

To Increase the EGR Quantity
– The E-VRV duty ratio is controlled*1. In the stable condition shown in the bottom center diagram, an increase in the current that is applied to the coil causes the attraction force FM in the coil to increase. When this force becomes greater than the vacuum force FV that acts on the diaphragm, the moving core moves downward. Along with this movement, the port from the vacuum pump to the upper chamber of the diaphragm opens. Consequently, the output
vacuum increases, which causes the EGR valve to open and the EGR volume to increase. Meanwhile, because “increased output vacuum equals increased FV”, the moving core moves upward with the increase in FV. When FM and FV are equal, the port closes and the forces stabilize. Because the vacuum circuit of the EGR is a closed loop, it maintains the vacuum in a stabilized state, provided there are no changes in the amperage.

To Decrease the EGR Volume
– A decrease in the current that is applied to the coil causes FV to become greater than FM. As a result, the diaphragm moves upward. The moving core also moves upward in conjunction with the movement of the diaphragm,
causing the valve that seals the upper and lower diaphragm chambers to open. Consequently, the atmospheric pressure in the lower chamber enters the upper chamber, thus reducing the output vacuum. This causes the EGR valve to close and the EGR volume to decrease. Because “decreased output vacuum equals decreased FV”, the moving core moves downward with the decrease in FV. When FM and FV are equal, the port closes and the forces stabilize.

pic1 114 E EGR System Operation

Written by Jack

March 11th, 2019 at 3:10 am

E-EGR System General Description

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The E-EGR system is an electronically controlled EGR system. The EGR system recirculates a portion of the exhaust
gases into the intake manifold in order to lower the combustion chamber temperature and reduce NOx emissions.
However, operation of the EGR system may reduce engine power output and affect drivability. For this reason, in the
E-EGR system, the engine ECU controls the EGR to achieve an optimal EGR amount.
Operation Conditions Example
– This operates in the operation region fulfilling the starting conditions below (one example).

pic1 112 E EGR System General Description

Written by Jack

March 11th, 2019 at 3:08 am

Other Injection Quantity Control

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Idle Speed Control (ISC) System
• The idle speed control system controls the idle speed by regulating the injection quantity in order to match the actual speed to the target speed calculated by the computer. The ISC can be automatic ISC or manual ISC.

Automatic ISC
– With automatic ISC, the engine ECU sets the target speed. The target engine speed varies with the type of transmission (automatic or manual), whether the air conditioner is ON or OFF, the shift position, and the coolant temperature.

pic1 109 Other Injection Quantity Control

Manual ISC
– The idle engine speed is controlled by the setting on the idle setting button at the driver’s seat.

pic1 110 Other Injection Quantity Control

Idle Vibration Reduction Control
– This control reduces engine vibration during idle. To achieve smooth engine operation, it compares the angle
speeds (times) of the cylinders and regulates injection quantity for each individual cylinder in the event of a large difference.

pic1 111 Other Injection Quantity Control

Written by Jack

March 11th, 2019 at 3:01 am

Fuel Injection Pressure Control

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The engine ECU calculates the fuel injection pressure, which is determined by the final injection quantity and the engine speed. The calculation is based on the coolant temperature and engine speed during start-up.

pic1 108 Fuel Injection Pressure Control

Written by Jack

March 11th, 2019 at 2:59 am

Fuel Injection Timing Control

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The fuel injection timing is controlled by the timing of the current applied to the injectors. After the main injection period is decided, the pilot injection and other injection timing is determined.

Main Injection Timing
– The basic injection timing is calculated from the engine speed (engine speed pulse) and the final injection quantity, to which various types of corrections are added in order to determine the optimal main injection timing.

Pilot Injection Timing (Pilot Interval)
– Pilot injection timing is controlled by adding a pilot interval value to the main injection. The pilot interval is calculated based on the final injection quantity, engine speed, coolant temperature, atmospheric temperature, and atmospheric pressure (map correction). The pilot interval at the time the engine is started is calculated from the coolant temperature and engine speed.

pic1 105 Fuel Injection Timing Control

Split Injection
– The purpose of split injection is to improve the startability of a cold engine. Before the conventional main injection takes place, this function injects two or more extremely small injections of fuel.

pic1 106 Fuel Injection Timing Control

Multi-Injection Control (Only for Some Models)
– Multi-injection control is when small injections (up to four times) are carried out before and after the main injection in accordance with the state of the main injection and engine operation. This interval (the time A-D in the diagram below) is based on the final injection quantity, engine speed, coolant temperature, and atmospheric pressure (map correction). The interval during start-up is based on the coolant temperature and engine speed.

pic1 107 Fuel Injection Timing Control

Written by Jack

March 11th, 2019 at 2:57 am

Fuel Injection Rate Control

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Although the injection rate increases with the adoption of high-pressure fuel injection, the ignition lag, which is the delay from the start of injection to the beginning of combustion, cannot be shortened to less than a certain period of time. Therefore, the quantity of fuel injected until ignition takes place increases (the initial injection rate is too high), resulting in explosive combustion simultaneous with ignition, and an increase in NOx and sound. To counteract this situation, pilot injection is provided to keep the initial injection at the minimum requirement rate, to dampen the primary explosive combustion, and to reduce NOx and noise.

pic1 104 Fuel Injection Rate Control

Written by Jack

March 11th, 2019 at 2:51 am

Fuel Injection Quantity Control

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General Description

• This control determines the fuel injection quantity by adding coolant temperature, fuel temperature, intake air temperature, and intake air pressure corrections to the basic injection quantity. The engine ECU calculates the basic injection quantity based on the engine operating conditions and driving conditions.

Injection Quantity Calculation Method
• The calculation consists of a comparison of the following two values: 1. The basic injection quantity that is obtained from the governor pattern, which is calculated from the accelerator position and the engine speed. 2. The injection quantity obtained by adding various types of corrections to the maximum injection quantity obtained from the engine speed. The lesser of the two injection quantities is used as the basis for the final injection quantity.

pic1 94 Fuel Injection Quantity Control

Set Injection Quantities
• Basic Injection Quantity
This quantity is determined by the engine speed and the accelerator opening. With the engine speed constant, if the
accelerator opening increases, the injection quantity increases; with the accelerator opening constant, if the engine speed rises, the injection quantity decreases.

pic1 95 Fuel Injection Quantity Control

• Starting Injection Quantity
This is determined based on the basic injection quantity for when the engine starts up and the added corrections for the starter S/W ON time, the engine speed, and the coolant temperature. If the coolant temperature is low, the injection quantity is increased. When the engine has completely started up, this mode is cancelled.

pic1 96 Fuel Injection Quantity Control

• Injection Quantity for Maximum Speed Setting
Determined by the engine speed. The injection quantity is restricted to prevent an excessive rise in engine speed
(overrun).

pic1 97 Fuel Injection Quantity Control

• Maximum Injection Quantity
This is determined based on the basic maximum injection quantity determined by the engine speed, and the added
corrections for coolant temperature, fuel temperature, intake air temperature, atmospheric temperature, intake air
pressure, atmospheric pressure, and full Q adjustment resistance (only for the 1st generation HP0 system), etc.

pic1 98 Fuel Injection Quantity Control

Corrections
• Cold Engine Maximum Injection Quantity Correction
When the coolant temperature is low, whether during start-up or during normal operation, this correction increases
the injection quantity.

pic1 99 Fuel Injection Quantity Control

• Intake Air Pressure Correction
When the intake air pressure is low, the maximum injection quantity is restricted in order to reduce the emission of black smoke.

pic1 100 Fuel Injection Quantity Control

• Atmospheric Pressure Correction
The maximum injection quantity is increased and decreased according to the atmospheric pressure. When the atmospheric pressure is high, the maximum injection quantity is increased.

pic1 101 Fuel Injection Quantity Control

• Injection Quantity Delay Correction for Acceleration
During acceleration, if there is a large change in the accelerator pedal opening, the injection quantity increase is delayed in order to prevent black smoke emissions.

pic1 102 Fuel Injection Quantity Control

• Full Q Adjustment Resistance (Only for 1st Generation HP0 Systems)
The full Q resistance is for correcting the injection quantity for a full load. The maximum injection quantity is increased or decreased by the car manufacturer to match to standards. There are 15 types of full Q adjustment resistance. The appropriate one is selected and used.

pic1 103 Fuel Injection Quantity Control

Written by Jack

March 11th, 2019 at 12:03 am