Modern excavator repair
Cases of experience and lessons in fault diagnosis of modern excavators (19)
4． After replacing the new fuel cut-off solenoid valve, the fault is resolved. For the above-mentioned faults, there are many reasons for the faults, but service personnel should accumulate their own maintenance experience and improve their own technical level of maintenance, and be good at observing and using the brain (such as observing that the fuel-cut solenoid valve is installed at the engine, Considering that the engine heat will affect the temperature change of the fuel cut solenoid valve and the resistance value of the holding coil will change), try to find the cause of the failure and solve the failure in the shortest time. Symptom: The boom is sinking too fast. User opinion: Fix the problem immediately. 1. On-site detection of the amount of boom subsidence (heat engine). The piston rod of the boom cylinder sinks 12 cm in 5 minutes under standard conditions, which is much larger than the standard value of 4 cm per minute. 2. From the general handling experience of such faults, 3. Check from the port relief valve first. Carefully observe the port relief valve, and you can hear the scream of hydraulic oil leaking. Touching the relief valve with your hand is very hot. It can basically be determined that the fault point is on the oil port relief valve.
The opening pressure of the measurement port relief valve was 38Mpa, the pressure was normal, and the failure was diagnosed as the seal of the port relief valve was not tight. 4． The correct method is to replace the new port relief valve. Because there are no accessories on site, temporarily adjust the forearm port relief valve (because of the forearm holding valve). After adjusting the pressure, measure the amount of boom subsidence, 3.5 cm per minute. For the above-mentioned faults, there are many causes of faults. According to the principles of simplicity and complexity, try to think and use your brain to quickly judge the fault and solve the fault. Symptom: When the machine is under load, the engine stops. User opinion: Fix the fault immediately, otherwise replace the engine assembly. 1. On-site inspection found that the engine works normally at no load, the engine is obviously weak at load, and the speed decreases until it goes out. 2. From the general handling experience of such faults, the fault is caused by poor diesel fuel supply. So from the diesel tank to clean up all diesel low-pressure oil circuits.
3. First open the drain valve under the diesel tank, drain the dirt and water in the fuel tank, clean the oil-water separator, and then check and clean the diesel filter. After running the test, the situation improved, but the fault still persisted. Further opening the oil pump's inlet pipe joint, it was found that the small filter there had been blocked by dirt, which caused the diesel oil supply to be poor. 4． Clean the clogged filter, reinstall the test drive, and troubleshoot. When shipping or regularly servicing the machine, repeat the importance of telling users the importance of clean oil. Usually pay attention to which parts and which connectors have filters in the work, and know the machine failure phenomenon that will occur if the filters are blocked. Symptom: The machine deflects to the right when walking. User opinion: Fix the problem immediately. 1. On-site inspection found that the vehicle veered to the right when moving forward or backward. 2. First, check the tension of the tracks on both sides, and the result is normal. 3. Secondly, the pilot pressures of the two pumps at high and low idle speeds were detected, and everything was normal. 4． then.
Replace the high pressure oil pipe of the travel motor from the center joint. When the machine is tested to run to the left, the right motor can be judged to be working normally. 5. Replace the 4 oil pipes for the left and right traveling oil supply between the main control valve and the center joint. When the machine is tested and found to be shifting to the left, it can be determined that there is no fault in the center joint. 6. Checked the main control valve to control the valve stem running left and right, found that the valve stem moves smoothly in the valve body, and there is no damage, the fault of the control valve is ruled out. 7. After swapping the two main pump regulators, it was found that the machine turned to the left when testing the machine. In this way, it can be determined that the fault is caused by the regulator (otherwise, the fault may be caused by the hydraulic main pump). 8. When the regulator was disassembled, several seal rings were found to be aging and damaged, resulting in inflexible valve stem movements and inability to properly adjust the angle of the swash plate. As a result, the displacement of the rear pump became smaller, the walking speed slowed down, and it shifted rightward. 9. Clean the pump regulator, replace all seals, and test the machine after installation.
Troubleshooting. Under the premise of familiar with the working principle of the machine, you should learn to use the "replacement method" and other methods to make logical inferences, so as to narrow down the fault scope and eliminate faulty components. Symptom: The speed of the excavator is slow. User requirements: Require a new machine. ． 1 . The agent service personnel checked the speed of the excavator in various modes when it was idle, and found that the actual speed was more than 300 revolutions (per minute) below the rated speed. Therefore, the user is informed arbitrarily that there may be a problem with the engine system of this excavator. ． 2 ． 部立即派驻点服务人员前往用户处，发现机器情况如用户所述，但一时未能解决问题。 The company's A / S department immediately sent service personnel to the customer's office and found that the condition of the machine was as described by the customer, but the problem could not be resolved. 部，公司相关人员查阅技术资料后将可能的原因（包括最简单的操作原因）告知驻点服务人员。 The resident service staff immediately reported to the company's A / S department, and the relevant personnel of the company informed the resident service staff of the possible reasons (including the simplest operating reasons) after consulting the technical information. ． 3 ． 格的位置处。 After another inspection, it was found that, for no reason, the manual throttle knob of the excavator's engine was turned at the position of the sixth grid.