Three Examples of Troubleshooting for Insufficient Engine Power in Komatsu WA500-6 Loader

(1) Fault phenomenon
A Komatsu WA500-6 loader suddenly experienced insufficient power during full-load operation, then flamed out, and the fault alarm device displayed an E03 alarm signal (this alarm signal indicates insufficient power).

(2) Troubleshooting
First, open the loader fault diagnosis system and find out the fault codes “CA559” and “CA2249”. The fault code “CA559” indicates that the fuel supply pump has low fuel pressure, and the fault code “CA2249” indicates that the fuel supply pump has extremely low fuel pressure. This indicates that the engine fuel supply system has a fault. Secondly, by pressing the hand oil pump to test the low-pressure oil circuit, it was found that the oil pressure in the low-pressure oil circuit was very low, while the normal low-pressure oil circuit pressure should be 0.15~0.3MPa. It was judged that a vacuum may have formed in the oil pipe.Thirdly, check the fuel pipe and find no blockage or bending and deflation of the pipe. This shows that there is no problem with the pipe. It is judged that the fault location should occur at the fuel pump or fuel filter. Then, the oil pump outlet pressure was tested. The measured oil pressure was 0.2MPa, which was within the normal range, indicating that the oil pump had no faults. Finally, the fuel filter was disassembled and inspected, and it was found that the fuel filter outlet was blocked by foreign matter. After replacing the fuel filter and testing the engine, the fault disappeared.

(3) Cause Analysis
The fuel enters from the fuel filter inlet and enters the fuel pump after passing through the fuel filter. The fuel filter outlet of the engine was blocked by foreign matter, and the fuel could not enter the fuel pump, resulting in insufficient engine power, flameout and inability to start.

(1) Fault phenomenon
During the operation of a Komatsu WA500-6 loader, its engine power decreased and it was powerless. The fault alarm device displayed an E03 alarm signal.

(2) Troubleshooting
First, the fault codes “CA559” and “CA452” were found in the fault diagnosis system. Fault code “CA559” indicates low injection pump pressure, and fault code “CA452” indicates low pressure in the high-pressure common rail tank. Secondly, perform an engine acceleration test. The maximum engine speed at this time was measured to be 1500r/min, which is 500r/min lower than the normal maximum value of 2000r/min. Analysis shows that the reason for the low maximum engine speed may be insufficient fuel supply in the fuel high-pressure oil circuit. Thirdly, check the engine fuel high-pressure oil circuit, and no pipeline blockage or bending and deflation were found. Next, test the injection pressure of the high-pressure oil pump. The injection pressure was measured to be 25MPa, which is within the normal range, indicating that the high-pressure oil pump is not faulty. The fault may be in the high-pressure common rail tank or injector. Then, adjust the engine speed to the total speed, and perform a cylinder cut-off test on the engine, and no abnormality was found. Finally, check the high-pressure common rail tank, and find that the valve core of the high-pressure common rail tank pressure limiting valve is stuck by foreign matter. After replacing the pressure limiting valve and testing the engine, the fault disappears.

(3) Cause Analysis
The structure of the pressure limiting valve is shown in Figure 1. When the pressure limiting valve is normal, if the fuel pressure in the high-pressure common rail tank does not reach the opening pressure of the pressure limiting valve, the spring in the pressure limiting valve will press the valve core tightly and the pressure limiting valve will not open. There is enough fuel in the high-pressure common rail tank to supply fuel to the injector. When the valve core is stuck by foreign matter, the valve core is not closed tightly and the fuel in the high-pressure common rail tank will overflow from the gap. The oil pressure in the high-pressure common rail tank is insufficient, which leads to insufficient fuel supply to the injector and reduced engine power.

(1) Fault phenomenon
During the operation of a Komatsu WA500-6 loader, the engine speed was high and low, the loader was unable to work, and the fault alarm device issued an E03 alarm signal.

(2) Troubleshooting
First, the fault code “CA1628” was found in the fault diagnosis system. The fault code was analyzed, but no explanation for this fault code was found in the data. According to the initial letters CA of the fault code and the fault phenomenon, we determined that the engine control module may have a fault. Secondly, we tested the engine speed and found that the fault only occurred after the engine had been running at full load and high speed for a period of time. When the fault occurred, the maximum speed was 1600r/min, and the speed could not be increased any further, which was 400r/min lower than the specified maximum speed. Analysis showed that the intermittent fault may be caused by poor contact of an electronic sensor or controller on the engine. Thirdly, we checked the controller on the engine and found no corrosion or loose connection of the pins. Then, we checked and tested all sensors and valves on the engine. When we checked the cylinder feedback sensor (EGR) of the secondary combustion control element, we found that the detection signal of the sensor was abnormal. When we checked the sensor, we found that the surface of the sensor had cracks. Finally, we replaced the cylinder feedback sensor and tested the engine, and the fault disappeared.

(3) Cause Analysis
After the cylinder feedback sensor cracked, the vibration of the engine caused the sensor to connect and disconnect from time to time, resulting in intermittent faults and high and low engine speeds. The above three faults show that the engine power reduction and the lack of driving and operation are not only related to the oil circuit, but also to the circuit. Although the alarm devices all show the E03 alarm signal, the fault locations are different and the fault codes are also different. When troubleshooting such complex faults, by referring to the fault codes and combining relevant practical experience, troubleshooting will become handy.