1, Calibration fault of electronic control module
After connecting the diesel engine electronic control module ECM, it is necessary to verify whether the ECM calibration is correct first. Verify the calibration revision history to correctly repair the calibration stored in the ECM. Based on the previous ECM image, the calibration code for the corresponding model can be determined, or the numerical value in the corresponding control part number (CPL code) can be compared on the quick service website using the diesel engine number as the basis.
During maintenance, it is possible to apply non applicable modules to the diesel engine. Therefore, it is important to ensure that the calibration code of the ECM is correct while confirming that there are no communication faults. If there is indeed a problem, it is necessary to recalibrate the ECM or replace the module with the correct code.
2, The parameter value of the intake manifold pressure sensor is incorrect
After confirming that there is no problem with the diesel engine computer module, it is necessary to check whether the parameter values of the intake manifold pressure sensor are correct. There are two reasons for the incorrect parameter values of the intake manifold pressure sensor: one is that the pressure sensor used is incorrect. There are many types of pressure sensors, and the applications of different models of diesel engines are not the same. Therefore, it is necessary to check the part number of the boost sensor, compare it with the part number in the Control Parts Catalog (CPL), and replace the boost sensor if necessary. The second reason is the malfunction of the sensor itself, which leads to parameter errors. Check its internal resistance and compare it with the standard to determine its quality. If the sensor is confirmed to be correct and working properly, then it is necessary to check the intake pipe and intercooler. Blockage of the intercooler or deformation of the intercooler core can cause the pressure at the intake manifold to be lower than normal. Ensuring sufficient air supply is an important means to solve the problem of diesel engine emitting black smoke. Check and repair the intake pressure sensor and intake system before proceeding with subsequent maintenance work.
3, Oil return pipe blockage fault
Blockage in the return oil pipeline of diesel engine fuel system is also a common fault point, especially after diesel engine maintenance, faults are more likely to occur. When replacing the fuel filter, the entire fuel system is open to the outside world, and external pollutants can easily enter the fuel system.
When maintaining a diesel engine, it is important to note that the requirements for fuel filters vary across different models and equipment, and not all require pre filling. Even if pre filling is required, attention should be paid to the method, usually filling around the filter element. When the diesel engine is running, the fuel is filtered before entering the fuel pump, and the pressure of the oil circuit can be detected to determine whether the return pipe is blocked. If the circuit pressure is higher than the normal value, the fuel injector supply pressure will be high, and the fuel injection amount per unit time will increase, resulting in incomplete combustion and the production of black smoke. After discovering the fault point during inspection, it is necessary to clean or replace components such as fuel pipes, check valves, and fuel tank ventilation pipes according to the actual situation.
4, The resistance of the intake system exceeds the technical specifications
The resistance of the intake and exhaust system is also a direct factor affecting the exhaust condition of diesel engines. The difference between this and checking the resistance of the intake system through the intake manifold is that the intake system refers to the air system before the intercooler and before and after the turbocharger. Low intake pressure is usually caused by a clogged air filter element. If the pressure indicator of the air filter shows red, it means that the air filter needs to be replaced. Relatively speaking, there are fewer cases of blockage on the exhaust side, but there have also been cases where cleaning cloth is left in the exhaust pipe after maintenance. For such faults, we need to clean or replace the air filter and intake/exhaust pipes based on the inspection findings.
5, Fuel pump system malfunction
The fundamental reason for diesel engines emitting black smoke is incomplete combustion of fuel, and the reason for incomplete combustion of fuel is the incorrect ratio of fuel to air. The fuel pump plays a role in establishing and controlling the fuel supply pressure, so ensuring its normal operation is the first step in checking the fuel system. After connecting to the computer, use the Insite service software to check if the fuel pump output pressure is within the normal range. If it is higher than the normal value, it is usually caused by a fuel pump malfunction. Firstly, it is necessary to analyze the following two points, namely whether the fuel pump pressure sensor and actuator are normal. If it is finally confirmed that there is an internal fault in the fuel pump, the fuel pump needs to be replaced. The fuel pump pressure sensor is used to detect the outlet pressure of the fuel pump. Check if the fuel pump pressure sensor is working properly. If there is a new sensor, alternative methods can be used to confirm its working condition. Otherwise, it is necessary to check its internal resistance, circuit continuity, and compare the sensor pressure and voltage to determine its status. If the fuel pump pressure sensor is indeed damaged, it needs to be replaced. The function of the fuel pump actuator is to regulate the outlet pressure of the fuel pump under the control of the ECM. The common malfunction of actuators is actuator jamming, and the fault code can also be seen in the computer. Follow the required fault tree to check step by step. It can also be monitored through computer data to observe changes in the outlet pressure of the fuel pump. If the air pressure value is higher than the normal value, it may be considered to replace the fuel pump actuator.
6, Turbocharger malfunction
If all the above components have been checked and there are no problems, the next step should be to focus on the turbocharger. If the turbocharger model used is incorrect, it cannot provide normal pressure. Firstly, check the turbocharger part number and compare it with the Control Parts Catalog (CPL). If there is indeed an error, the turbocharger needs to be replaced, otherwise it is necessary to check whether the oil seal of the turbocharger is leaking. There are sealing rings on both sides of the turbocharger middle section, which are used to separate the lubrication chamber from the intake and exhaust sides. When the oil seal is damaged or there is an obstacle on the intake side, causing low pressure on the intake side, the oil will be blown to one end of the intake impeller under the pressure on the exhaust side, causing the oil to enter the cylinder, while the intake air volume decreases and the exhaust smoke turns black. During inspection, it is generally only necessary to check for oil stains at the intake connection of the turbocharger. If a problem is found with the turbocharger during inspection, it needs to be replaced. After replacement, observe its operating condition. If the fault no longer occurs, it can be resolved.
7, Timing pressure sensor and timing actuator malfunction
If the above maintenance does not solve the problem, it is necessary to check whether there is a malfunction in the timing pressure sensor and actuator. During on-site maintenance, the most common issue encountered is actuator jamming. If the actuator gets stuck due to factors such as oil quality, it can cause the fuel supply pressure to be uncontrolled by the ECM, resulting in excessive fuel supply and black smoke from the diesel engine. The simplest method to check the timing pressure sensor and actuator is to replace the experimental method. If there are no new or confirmed actuators and sensors on site, it is necessary to check the action of the actuators and the pressure data of the sensors in the computer to analyze and find faults. For a timing pressure sensor, its internal resistance and corresponding pressure can be checked to determine if there is a malfunction. If the formal pressure sensor and timing actuator are damaged, they need to be replaced in a timely manner.
8, Atmospheric pressure sensor malfunction
The malfunction of atmospheric pressure sensors is a common problem in cold working environments. Incorrect atmospheric pressure values can cause the ECM to issue incorrect fuel injection commands, and excessive fuel injection is also a cause of black smoke in diesel engines. Do not immediately replace the sensor when this malfunction is detected. The combustion exhaust gas contains moisture, and in cold weather, the internal icing phenomenon of the atmospheric pressure sensor often occurs. To address this, it can be replaced and dried before continuing to be used. If the internal damage of the atmospheric pressure sensor is found during inspection, a new part needs to be replaced.
9, Diesel engine speed sensor malfunction
Damaged speed sensors can also affect the control of fuel injection quantity in diesel engines. Ensuring that the diesel engine speed sensor is functioning properly and installed properly is the key to solving this problem. Firstly, it is necessary to ensure that the sensor is functioning properly, with an intact appearance and no gaps or stains on the sensor head. Measure the internal resistance of the speed sensor again. If it is infinite, it indicates an internal short circuit and needs to be replaced. During installation, it is necessary to strictly follow the technical standards, that is, when it is screwed into contact with the flywheel teeth, it should be rotated in the opposite direction for 3/4 of a turn. If the gap between the sensor and the flywheel is too large, it may not sense any signal changes, and if it is too close, it may damage the sensor.
10, Fuel injector malfunction
If there are no issues with the above, it is necessary to check if the fuel injector is faulty. If the fuel injector is damaged, the fuel will enter the combustion chamber directly in the form of oil droplets, causing incomplete combustion of diesel and resulting in black smoke from the diesel engine.
The key points for checking fuel injector faults are as follows: Firstly, determine which side of the injector is faulty or both sides are faulty based on whether black smoke is emitted from one side or both sides. Secondly, the exhaust temperature of each cylinder can be detected using the CENSE on the diesel engine. This function is very practical on the QSK60 diesel engine. When a cylinder burns poorly, its exhaust temperature will inevitably be lower than the normal temperature. If the fault lasts for a long time and the fuel injector does not atomize well for a long time, it will cause oil stains to appear at the contact position between the corresponding cylinder exhaust pipe and the cylinder head. This is also a good way to diagnose fuel injector faults. If a malfunction is found in the fuel injector, replace the corresponding fuel injector.
11, Top mounted mechanism malfunction
If all the above fault points have been checked and there are no faults, then it is necessary to consider whether it is an adjustment issue with the overhead mechanism. Generally, after major repairs to diesel engines or maintenance involving the removal of overhead mechanisms, this needs to be given special consideration. If the diesel engine has been used normally for a period of time, the possibility of such faults is relatively small. If the inspection shows a malfunction in the overhead mechanism, readjust the settings of the overhead mechanism. In addition to the basic reasons that can cover the types of on-site faults mentioned above, it is also necessary to consider some rare but more serious types of faults. For example, whether the crankcase pressure of a diesel engine is too high, whether the cylinder compression pressure is too low, whether the static fuel injection timing is correct, and whether the piston, camshaft, and other parts are damaged.
12, Conclusion
This article mainly focuses on the QSK60 diesel engine as the research object, and provides a detailed overview of the fault diagnosis of diesel engines, which is of great significance for the maintenance and upkeep of diesel engines. The types of diesel engine faults are complex and involve many reasons. When conducting actual fault diagnosis, it is necessary to combine the actual situation, collect on-site fault information, and communicate with on-site operators in a timely manner. To ensure the efficient operation of equipment, intelligent detection technology can be applied as a detection method to the troubleshooting of mining machinery equipment, gradually achieving automation of fault detection and achieving the goal of quickly identifying and handling faults.
