The Ultimate Guide to Liebherr Excavator Parts: Everything You Need to Know

Digging powerlessness can be divided into two situations: one is digging powerlessness, the engine does not hold back, and the load feels very light; the second is digging powerlessness, when the boom or dipper stick is extended to the bottom, the engine is seriously held back or even stalled.

①, digging powerlessness but the engine does not hold back. The magnitude of the digging force is determined by the output pressure of the main pump, and whether the engine holds back depends on the relationship between the oil pump absorption torque and the engine output torque. The engine does not hold back, indicating that the oil pump absorption torque is small and the engine load is light. If the working speed of the excavator is not obviously abnormal, the maximum output pressure of the main pump, that is, the system overflow pressure, should be checked in particular. If the overflow pressure measurement value is lower than the specified value, it indicates that the overload overflow valve setting value of the hydraulic circuit of the mechanism is incorrect, resulting in premature overflow of the mechanism and powerlessness. The machine can be adjusted by turning the adjustment screw.

②, digging powerlessness, engine holding back. The engine holding back indicates that the absorption torque of the oil pump is greater than the engine output torque, causing the engine to overload. This fault should first check whether the engine speed sensing system is normal, and the inspection method is similar to the engine inspection method described above. After the above detailed inspection and troubleshooting, the engine speed sensing system will resume normal function, the engine stalling phenomenon will disappear, and the digging force will return to normal.

Symptoms of a faulty cooling system include high hydraulic oil temperature, reduced pump efficiency and overheating of the hydraulic system.

8 reasons for the engine speed drop of the excavator, 6 solutions are here!

As the name suggests, engine speed drop means the failure of the engine speed drop during the operation of the excavator. There are two manifestations of speed drop, one is a slight speed drop within 200 revolutions, and the other is a serious speed drop above 300 revolutions, which is likely to cause the excavator to suddenly shut down. There are 8 main reasons for the engine speed drop of the excavator.

1. The diesel oil circuit of the excavator is faulty. Generally speaking, when the diesel oil circuit is blocked, it may cause the speed drop phenomenon.

2. The hydraulic system of the excavator has a fault, so that the hydraulic pump cannot change the displacement normally, causing the system pressure to be too high, and the speed drop may also cause a machine failure.

3. The output power of the excavator engine itself is insufficient, the output power is lower than the rated power, and the speed is too low. There is also a problem with the main pump.

4. The engine uses fuel of poor quality or the water content of the fuel is too high, which will lead to insufficient engine power and speed drop.

5. When the air intake system leaks or is blocked, the engine will be short of air supply, resulting in incomplete combustion of fuel, and there will be speed drop and black smoke failure.

6. Due to the large gap of the solenoid valve, the fuel supply is insufficient, which causes the engine to drop.

7. The joint of the fuel supply circuit of the fuel system is loose or the pipeline is broken, causing fuel leakage or foreign matter blockage, resulting in insufficient fuel supply. In addition to speed drop, it may also cause flameout.

8. There are many reasons for speed drop, such as incorrect valve clearance, wrong injection timing, damaged turbocharger, faulty brakes, etc.

Having said so many reasons for the speed drop of the excavator engine, what should we do when the speed drop occurs?
The solutions are all here!

1. First, check whether the diesel used in the excavator is deteriorated, whether there are impurities in the oil, and whether the oil circuit is blocked.

2. Check the valve clearance of the excavator engine and the speed of the engine.

3. Check the intake pipeline, clean the air pre-filter and air filter element, and start the engine again.

4. Check whether the speed drop of the excavator occurs when the engine is under load?

5. Carefully check the engine to see if the engine failure causes the speed drop of the excavator engine.

6. In addition, the electronic control, hydraulic system, fuel system, etc. need to be checked.

Testing engine performance includes checking the engine's start-up, running, acceleration, and emissions. Use diagnostic equipment to read engine fault codes, test the fuel system and ignition system, and regularly conduct compression tests and exhaust analysis.

Possible air in the system, clogged filter, or worn pressure relief valve.

Solution: Bleed air from the system, clean or replace filter, replace pressure relief valve.