Fault description: under normal working conditions, the engine of Caterpillar 312c excavator suddenly loses speed. After the excavator works for a period of time, it returns to normal.
Fault analysis of "Caterpillar 312c excavator engine speed drop" in excavator maintenance: the speed drop of excavator during operation is caused by electrical problems:
1. In order to reduce the fuel consumption of the engine, the excavator has set the function of automatic idling. If the switch is pressed or the control circuit is faulty, the automatic idling will not be released, and the engine speed will drop and the working speed will be slow.
2. Hydraulic problems: the excavator stops for about 6 seconds. The controller checks and detects that there is no pressure output from the pilot, and the engine speed drops to 1450 rpm, thus achieving the goal of reducing fuel consumption.
3. If the pilot pressure switch is damaged, the automatic idling cannot be automatically released, causing the engine to have no automatic idling function, speed loss or unstable speed.
Cause analysis of fault: the switch of travel pilot pressure was damaged, which caused the fault, and the excavator maintenance "Caterpillar 312c excavator engine dropped speed"
Fault analysis:
1. Since the fault is accidental, it needs to be observed to eliminate it. After the engine is started, the automatic idling is canceled. The fault disappears during the operation, and it is judged that the control system of automatic idling is faulty.
2. Press the automatic idle switch and pull off the switch connector of the travel pilot pressure. The maximum speed of the engine reaches 2300 rpm. After the two ends are short circuited, the speed of the engine drops to 1450 rpm. It can be judged that there is no fault in the circuit.
3. Replace the switch of travel pilot pressure, and the fault was eliminated after the test run. Troubleshooting experience: the principle of the excavator automatic idle control system: the pilot handle acts - the pilot pressure switch disconnects - the speed of the motor - engine of the controller - accelerator rises rapidly, the pilot handle does not act - the pilot pressure switch connects - the controller (6 seconds delay) - the speed of the motor - engine of the accelerator drops to 1450 rpm.
Because the pilot pressure switch has a very small damping hole, if the pilot oil is not clean, it will easily be blocked, and it is not easy to clean it. It can only be replaced. Therefore, the cleaning of the hydraulic oil can prevent the occurrence of most hydraulic system faults.
