Slow bucket and slewing actions fault

Release time:

2025-11-27

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I. Troubleshooting Approach

(1) Hydraulic aspects: The main spool is jammed, resulting in slow operation; the bucket combine solenoid valve is malfunctioning, causing slow bucket movement; the swing hydraulic system operates slowly, affecting swing motion; and the main pump regulator is faulty, leading to slow working performance, among other issues.

(2) Electrical aspects: A fault in the wiring or abnormalities in the solenoid valves and sensors can cause abnormal power control of the main pump.

(3) Control aspect: A controller program malfunction caused the transmitted signals to become abnormal.

II. Troubleshooting Process

(1) The wiring was inspected, and no short circuits or open circuits were found. The voltage of sensor No. 50’s power line was measured at 5V; the voltage ranges of signal lines 501 and 502 were between 0.5V and 4.5V; and line No. 00 showed a voltage of 0V. Both the wiring and the sensors are functioning normally.

(2) After powering on the equipment and starting up the machine, no fault alarms were detected. We entered the display menu to check the hydraulic system signals. When performing digging operations, Pump 2 pressure reached 377 kg, exceeding the standard value of 343 kg.

(3) The resistance of the proportional solenoid valve was checked and found to be 18 ohms. There is no sticking or jamming of the valve spool, indicating that the solenoid valve is functioning properly.

(4) Disassemble the regulator from the plunger pump and inspect the servo piston inside the chamber to ensure it moves freely without any sticking or internal leakage. The inspection confirmed that the servo piston is in good condition.

(5) When manually operated, the regulator’s actuator fork showed no signs of sticking or jamming, indicating that the regulator is functioning normally.

(6) When performing the slewing motion alone, the slewing motion is extremely slow, and the pressure of Pump 1 is only 47 kg. The pressure of Pump 2, however, keeps fluctuating. Upon further observation, it was found that when the slewing motion is performed alone, both the system pressures and current values of Pump 1 and Pump 2 are continuously changing. Under normal circumstances, Pump 1 should supply power to the slewing motor, and the controller should only output varying current values to Pump 1—not to Pump 2. This indicates that the controller’s output signal is abnormal.

(7) When performing the walking motion alone, or the right-side walking motion alone, it was found that the controller was not outputting normal current values for Pump 1 and Pump 2. Further investigation revealed a fault in the controller’s program. After reconnecting the OBD and updating the controller’s program, the fault was resolved.

III. Failure Summary

(1) The customer’s original vehicle controller was internally damaged and produced no signal output whatsoever. Therefore, we replaced it with a new controller that comes with its own built-in program. During the troubleshooting process, we mistakenly assumed that the new controller’s program was incompatible with the original vehicle system, which led us to take a long detour and waste a great deal of time.

(2) When troubleshooting, you should try each operation multiple times, familiarize yourself with the working principle of each operation, and observe the changes in the data displayed on the screen. Only then can you more accurately understand the fault symptoms, identify the root cause of the failure, and promptly repair the malfunction.

(3) When troubleshooting, follow the sequence of “easy first, then difficult; external first, then internal; key issues first, then general ones” to analyze and resolve after-sales problems.

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