Refined troubleshooting of automatic idling failure of excavator engine

Troubleshooting and repair of automatic idle fault of υδραυλικός εκσκαφέας

During port operation, an abnormal condition occurred in a υδραυλικός εκσκαφέας after the automatic idle function of the engine was enabled. When the working device was stationary, the engine speed would suddenly soar, and after running for a while, it would automatically fall back to the automatic idle state. Moreover, this phenomenon was repeated when the working device was not in motion throughout the whole process, and there was no regular time interval between the occurrence of the fault.

The automatic idle function was set on this excavator. The original intention was to reduce the engine speed when the working device stopped moving, thereby reducing the engine power loss and achieving the purpose of energy saving and consumption reduction. Its working principle is based on the controller's monitoring of the excavator's pilot pressure, and judging whether the pilot handle is in motion by the state of the pilot pressure switch. If the pilot handle is stationary, the controller will reduce the engine speed to the preset idle state; once the pilot pressure switch state change is detected, it is determined that the pilot handle is in motion, and the engine speed will be immediately increased to the working speed. Since the excavator is not equipped with a dismounting walking device to adapt to the port environment and reduce manufacturing costs, one of the two oil ports of the pilot pressure switch is idle.

After in-depth analysis, the following four reasons are considered to be the main reasons for the failure of the automatic idle function of the engine:

First, the control program of the controller is abnormal, resulting in unstable output of the engine speed signal;

Second, the pilot pressure switch fails and cannot accurately feedback the actual working status of the excavator;

Third, there is a hidden danger of virtual connection in the electrical control circuit, which causes the signal received by the controller to be distorted;

Fourth, the pilot hydraulic control circuit is blocked, making the pilot pressure switch unable to truthfully reflect the actual operation situation.

Based on the above analysis, the maintenance personnel carried out detailed troubleshooting:

1. Automatic idle function test: Turn on the automatic lock function, and closely observe the automatic idle state of the engine without operating the pilot handle. It has been confirmed that the three-level automatic idle function of the engine can be realized normally, but after a period of automatic idle operation, the speed will still increase for no reason, and then return to idle, and this phenomenon occurs repeatedly and irregularly.

2. Controller and circuit inspection: Unplug the connector of the pilot oil pressure switch. At this time, the signal collected by the controller is high level. Even if the pilot handle does not move, the engine can still enter the automatic idle state normally without any abnormality. Short-circuit the two ends of the connector, and the controller collects a low-level signal. When the pilot handle is stationary, the engine does not enter the automatic idle state. This series of inspections shows that there are no faults in the controller program and electrical control circuits.

3. Pilot pressure switch troubleshooting: Interchange the oil port in use with the idle oil port of the pilot pressure switch. When the machine is tested again, the fault disappears. It can be determined that the pilot pressure switch is damaged. After replacing the new pilot pressure switch, the long-standing fault has been completely solved.

In this troubleshooting, the maintenance personnel, based on an in-depth analysis of the working principle, cleverly used short-circuiting, disconnecting the line, and changing the installation method of the components to quickly lock the fault location, which not only greatly improved the repair efficiency and quality, but also successfully saved maintenance time and cost, providing a strong guarantee for the efficient and stable operation of the equipment.

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