1. Why is it difficult to start an excavator in winter:
It is not only determined by its own technical status, but also affected by the outside temperature. Starting is more difficult at low temperatures in winter, mainly due to the following reasons.
- In winter, the climate is cold, the ambient temperature is low, the viscosity of the engine oil increases, and the friction resistance of each moving part increases, which reduces the starting speed and makes it difficult to start.
- The battery capacity decreases as the temperature drops, further reducing the starting speed.
- As the starting speed decreases, the leakage of compressed air increases, and the heat dissipation of the cylinder wall increases, causing the temperature and pressure of the air to be greatly reduced at the end of compression, which increases the delay period of diesel ignition, and in severe cases, it may even fail to burn.
- The viscosity of diesel fuel at low temperatures increases, which reduces the injection speed. In addition, the swirl speed, temperature and pressure of the air at the end of compression are relatively low, which makes the atomization quality of the diesel fuel injected into the cylinder poor and difficult to quickly form a good atomization with the air. The flammable gas will ignite and burn in time, or even fail to catch fire, resulting in difficulty in starting.
2. What are the conditions for good starting performance of an excavator:
- There must be sufficient starting speed. The starting speed is high, the gas leakage in the cylinder is small, the time for the compressed air to transfer heat to the cylinder wall is short, and the heat loss is small, which increases the gas temperature and pressure at the end of compression. Generally, the rotation speed is required to be above 1000r/min.
- The sealing of the cylinder should be good. This can further reduce the amount of air leakage and ensure that the gas has sufficient combustion temperature and pressure at the end of compression. The compression pressure of the cylinder shall not be lower than 80% of the standard value.
- The matching clearance between the engine and the running parts is required to be appropriate and well lubricated.
- The battery must have sufficient starting capacity and the technical condition of the starting circuit is normal.
- The starting oil quantity meets the requirements, the injection quality is good, and the injection advance angle must meet the requirements.
- Use fuel that meets the requirements.
3. Diagnosis and repair of mechanical faults if the crankshaft cannot rotate when the excavator is started. When the engine is started and the starting system is intact, press the start switch. If the starter makes a sound but the crankshaft cannot rotate, it is a mechanical failure. The reasons why the engine crankshaft cannot rotate are as follows:
- The starter and flywheel teeth are not meshing well. The ring gear and starter gear will collide when starting the engine, causing tooth damage or single-sided wear of the teeth. If more than three teeth in a row are damaged or severely worn, it will be difficult for the starter gear and ring gear teeth to mesh.
- Sticky cylinder. When the engine temperature is too high, the engine stalls and the heat is difficult to dissipate. The piston rings at high temperatures adhere to the cylinder and cannot be started after cooling.
- The crankshaft is locked. Due to a failure in the lubrication system or a lack of engine oil, the sliding bearing causes dry friction, which eventually locks the crankshaft and prevents it from starting.
- The fuel injection pump plunger is stuck.
4. Diagnosis that the excavator can rotate when starting, but cannot start (no smoke in the exhaust pipe):
When starting the engine, there is no smoke coming out of the exhaust pipe, and there is no explosion sound. This is generally an oil circuit problem. The detailed analysis is as follows.
- There is no oil in the fuel tank.
- The fuel filter and oil-water separator are clogged.
- The low-pressure oil line does not supply oil.
- The fuel injection pump does not pump oil.
- There is air in the oil line.
- The valve phase is misaligned. The opening moment of the valve is not coordinated with the stroke of the piston in the cylinder. For example, when the piston performs the compression stroke in the cylinder, the intake and exhaust valves are opened, and the fresh air is driven out of the cylinder, so that there is no combustion gas in the cylinder and it cannot be started.
- fuel injection pump is broken and is in a closed state, so diesel cannot enter the high-pressure chamber.
5. Diagnosis of difficulty in starting the excavator or failure to start, and a large amount of white smoke emitted from the exhaust pipe. The reason why a large amount of white smoke is emitted from the exhaust pipe when the engine is started is analyzed as follows:
- There is water in diesel fuel. The water evaporates into steam in the cylinder and is discharged from the exhaust pipe.
- The cylinder head bolts are loose or the cylinder gasket is damaged, allowing cooling water to enter the cylinder.
- There are trachoma or cracks somewhere in the cylinder block or cylinder head, and water enters the cylinder and evaporates out.
6. Diagnosis of difficulty in starting the excavator or failure to start, and a large amount of gray and white smoke coming out of the exhaust pipe. The engine has difficulty starting, and a large amount of gray smoke is emitted from the exhaust pipe as diesel vapor:
- The engine temperature is too low and diesel is not easy to evaporate and burn.
- Poor atomization of the fuel injector
- The oil supply time is too late.
- The fuel supply is too small and the mixture is too thin.
- The cylinder leaks too much and cannot reach the ignition temperature after compression.
7. Diagnosis that the excavator is difficult to start or cannot start, and a large amount of black smoke is emitted from the exhaust pipe. The engine is difficult to start and a large amount of black smoke is emitted from the exhaust pipe, which is the result of incomplete diesel combustion:
- Diesel quality is poor
- The air intake is not smooth and the air filter is clogged.
- The injection timing is adjusted too early.
- The fuel injector needle valve has poor sealing and oil leakage occurs.
- The injection pressure is too low.
- The fuel supply volume of the fuel injection pump is too large and the combustion deteriorates.
- The cylinder pressure is low and the atomization is poor.
8. Diagnosis of difficulty in hot starting of excavator:
The engine starts well when cold, but stalls after running for a period of time when the temperature rises. The difficulty in starting again is mainly caused by the severe wear of the fuel injection pump plunger pair and the fuel injector needle valve pair. When a hot car is started, due to the high temperature of the fuel injection pump and fuel filter, the fuel viscosity decreases, and the starting speed is low, most of the diesel leaks from the worn gaps, resulting in insufficient starting oil and unable to start.
9. Diagnosis and treatment of excavator with normal low speed and short-term high speed with too little smoke exhaust. The engine idles well, and the speed can rise quickly when the throttle is pressed, but the speed does not rise easily when the throttle is pressed continuously, and the vehicle is unable to drive, or cannot drive in medium or higher gears. This is caused by insufficient low-pressure fuel supply:
- The diesel filter or oil-water separator is clogged.
- The low-pressure oil line is not smooth.
- The oil supply pump has insufficient oil supply or the oil inlet filter is clogged.
- The fuel tank cap air inlet valve fails. All the above situations can cause insufficient fuel pressure in the low-pressure oil chamber of the fuel injection pump, and can only maintain the fuel supply required for small loads. When large and medium loads require more fuel supply, it cannot be satisfied, resulting in inability to drive.
10. Diagnosis of the excavator's normal low speed but no high speed and too little smoke exhaust:
The engine speed is good at low speed, but the speed cannot rise during acceleration and the driving is weak. This is caused by insufficient circulating oil supply.
- The fuel injection pump is improperly adjusted, which reduces the fuel supply.
- The elastic force of the speed regulator spring is reduced due to fatigue. When the accelerator is pressed to the bottom, the fuel volume adjustment lever cannot move forward, causing the fuel injection pump to reduce the fuel supply and the engine cannot reach the rated speed.
- The plunger and sleeve of the fuel injection pump, the needle valve of the fuel injector, and the needle valve body are severely worn, resulting in increased diesel leakage during pumping and a relatively reduced fuel supply.
- The throttle control lever is improperly adjusted, or the accelerator pedal pin is too wide, so that the accelerator pedal cannot be in place, resulting in too little fuel supply at full load.
- There is air in the oil line.
11. The fault diagnosis analysis of the excavator lacking power and emitting ash and white smoke is as follows:
The engine power is insufficient and gray smoke is emitted from the exhaust pipe, which is usually caused by the fuel injection time being too late. At this time, not only is the high-speed operation poor, the acceleration is insensitive, but the temperature is easily too high.
- The injection advance angle is too small.
- The fuel injector has poor atomization.
- The engine temperature is too low.
- There is water in the cylinder.
- There is water in diesel fuel.
12. Analysis of the causes of failure of the excavator due to insufficient power and thick black smoke:
The engine has insufficient power and uneven speed. There are two phenomena of thick black smoke being emitted from the exhaust pipe: one is continuous black smoke; the other is intermittent black smoke and the engine is shaking. The engine lacks power and continuously emits black smoke. This is caused by excessive fuel supply in most or all cylinders of the engine, imbalance in the mixing ratio of fuel and air, severe lack of oxygen during combustion, incomplete diesel combustion, and suspended free carbon elements. It is formed by exhaust gas being discharged together. If the exhaust pipe emits black smoke intermittently and is accompanied by a "chugging" sound, it means that the combustion in some cylinders is incomplete. The reasons are summarized as follows.
- Improper debugging of the fuel injection pump results in excessive fuel supply and incomplete combustion.
- The injection quality of most injectors is poor.
- When the oil supply is incorrect.
- The opening height of the intake valve is reduced and the opening time is delayed, resulting in insufficient air intake.
- The air filter element is too dirty or the air filter is installed incorrectly, causing the air to not flow smoothly.
- The supercharging efficiency of the supercharger decreases.
- The fuel quality is too poor.
13. Diagnosis and treatment of excavator insufficient power and blue smoke emission:
The engine emits blue smoke when the engine is at low temperature or under low load. When the temperature rises, it emits dark gray smoke and lacks power.
- The air intake is not smooth, causing the oil in the supercharger to be sucked into the cylinder and burned.
- There is too much oil in the oil pan and the oil exceeds the maximum limit.
- Put engine oil into the valve guide.
- The cylinder has serious oil leakage.
- The supercharger rotor shaft is severely worn and the oil retaining ring is damaged, causing the supercharger to fail to reach the rated speed and leaking oil.
14. Why is the supercharger the assembly most prone to failure on the engine?
Because the rated operating speed of the supercharger is more than 130,000 rpm, and it is located at the outlet of the exhaust manifold, the temperature is extremely high (above 800°C), and the inlet and exhaust pressures are also large, that is, high temperature, high pressure, and high speed. , so the requirements for lubrication, cooling and sealing of the supercharger are relatively high. In order to ensure the service life of the supercharger, the design must ensure the lubrication and cooling of the floating bearing of the supercharger. At the same time, it is required to do the following during use.
- After starting, the engine should be idle for 3-5 minutes and do not load immediately to ensure good lubrication of the supercharger. The main reason is that the supercharger is located at the top of the engine. If the supercharger starts running at high speed immediately after the engine is started, the oil pressure will not rise in time to supply oil to the supercharger, causing the supercharger to be damaged due to lack of oil and even burn out. Damage the entire supercharger.
- The idling time should not be too long, generally no more than 10 minutes. Too long idling time can easily cause oil leakage at the compressor end.
- Do not shut down the engine immediately before parking, but idle for 3-5 minutes to allow the supercharger speed and exhaust system temperature to drop to prevent heat regeneration, oil coking, bearing burnout and other failures. Frequent incorrect use can damage the supercharger.
- For engines that have not been used for a long time (generally more than 7 days), or engines with new superchargers, engine oil should be added to the oil inlet of the supercharger before use. Otherwise, the service life of the supercharger will be reduced or the supercharger will be damaged due to poor lubrication. .
- Regularly check whether there are loose air/oil leaks at each connection part and whether the oil return pipe is unobstructed. If any, they should be eliminated in time.
- Ensure the air filter is clean and replace it regularly as required.
- Replace the engine oil/oil filter regularly.
- Regularly check the radial and axial clearance of the supercharger shaft. The axial clearance should be no more than 0.15 mm. The radial clearance is: the clearance between the impeller and the pressure housing should be no less than 0.10 mm. Otherwise, professionals should be asked to repair it to avoid expanding losses.
15. Why is it that after the supercharger on some excavator engines is damaged, the life of the new supercharger is often very short：
- The lubricating oil is not clean.
- There are impurities in the oil passage.
- There is foreign matter in the intake and exhaust pipes.
16. Cause analysis and troubleshooting of the excavator's no idling speed:
The engine has no idling speed, which generally manifests itself as stalling when the accelerator is placed in the idling position. When the accelerator is slightly increased, the speed increases quickly and cannot operate stably at low speeds.
- The idle speed spring of the speed regulator is too soft or broken.
- The sensor element of the speed regulator is excessively worn.
- The fuel injection pump plunger is seriously worn.
- The temperature is too low.
- Cylinder pressure is too low.
17. Cause analysis and troubleshooting of the excessively high idle speed of the excavator:
The engine idle speed is too high, which is manifested in that when the accelerator is lifted, the engine speed is still higher than the specified idle speed value.
- The throttle lever is improperly adjusted.
- The throttle return spring is too soft.
- The idle speed limit block or adjustment screw is out of adjustment.
- The idle spring is too hard or the preload force is adjusted too large.
18. Cause analysis and fault diagnosis of the excavator’s unstable idling speed: The engine’s unstable idling speed is manifested by sudden speed and slowness during idling operation, or vibration, causing the machine to stall during rapid deceleration or gear shifting. Detailed reason analysis is as follows.
- There is air in the oil line.
- The low-pressure oil line has poor oil supply.
- The idle speed stabilizing device is improperly adjusted.
- The atomization of the fuel injector is poor.
- The fuel injection pump supplies uneven fuel.
- The pins and forks of each connecting rod of the speed regulator are worn too much.
19. Analysis of the reasons for sudden flameout of the excavator during operation: Sudden stalling of the engine during operation refers to the phenomenon that the engine stalls rapidly due to factors other than the driver's operation without releasing the accelerator while the engine is running, and cannot be restarted after stalling. This phenomenon is generally caused by mechanical failure. The reasons are as follows.
- The fuel injection pump drive tooth is broken and the transmission gear is faulty.
- The fuel injection pump shaft is broken.
- The moving parts inside the engine are stuck.
- The fuel injection pump control rod and connecting pin fell off.
20. Analysis of the reasons for the slow stalling of the excavator during operation: The engine stalls slowly without releasing the accelerator, which is generally caused by insufficient oil supply or interruption of oil supply. Its performance is that the engine gradually becomes weak during operation and finally automatically shuts down
- The diesel in the fuel tank is exhausted.
- The vent valve of the fuel tank cap is blocked.
- The fuel filter or oil-water separator is clogged.
- The oil supply pipeline is broken or a lot of air has penetrated.
- The oil transfer pump does not work.
- There is water in the fuel tank.
21、Maintenance Schedule for an Excavator：
Performing routine inspections allows you to identify any visible damage or signs of wear. Inspect the excavator’s components, including the boom, bucket, tracks, hydraulics, and electrical systems. Additionally, make sure to clean the machine thoroughly after each use, removing dirt, debris, and accumulated grime.
- Regularly changing the engine oil and filter is essential for the smooth operation of an excavator. Follow the manufacturer’s guidelines regarding the recommended oil type and change intervals. Keep a record of oil changes to ensure timely replacements.
- Maintaining clean hydraulic fluid is vital for proper excavator function. Regularly inspect the hydraulic system for leaks and check the fluid level. Replace the hydraulic filters as recommended by the manufacturer to prevent contamination and maintain optimal performance.
- Greasing the excavator is necessary to ensure smooth movement and minimize friction. Apply grease to the specified points, including pins, bushings, and bearings. The greasing frequency will be discussed in more detail later in this article.
- The excavator’s tracks endure significant wear and tear. Regularly inspect the tracks for any signs of damage, such as loose or worn-out components. Adjust the track tension according to the manufacturer’s recommendations, and replace any damaged parts promptly.
- Inspect the electrical system for loose connections, damaged wires, or faulty components. Ensure the battery is in good condition, and all electrical connections are secure. Regularly test the lights, gauges, and other electrical features to verify their functionality.
- The cooling system is critical to prevent engine overheating. Regularly inspect the radiator, coolant level, and hoses for leaks or damage. Clean the radiator and remove any debris or obstructions to maintain proper airflow.
22、Servicing Frequency for Mini Excavators：
The servicing frequency for mini excavators generally follows similar guidelines as larger excavators. However, it’s essential to consult the specific manufacturer’s recommendations for your mini excavator model. Mini excavators may have different service intervals depending on their size, usage, and operating conditions. Adhering to the manufacturer’s guidelines will help keep your mini excavator in optimal condition.
23、Best Tools for Excavator Repair：
To effectively repair and maintain an excavator, having the right tools is crucial.
Here are some essential tools you should consider having in your toolbox;
- Basic Hand Tools for Excavator Repair
- Wrenches, socket sets, and pliers for general repairs and adjustments.
- Screwdrivers for removing panels and accessing components.
- Hammers and pry bars for removing stubborn parts.
- Torque wrenches for precise tightening of fasteners.
- Diagnostic Tools for Excavator Repair
- Multimeter for electrical troubleshooting.
- Pressure gauges for hydraulic system diagnostics.
- Diagnostic software and scanners for engine diagnostics.
24、Specialised Tools for Excavator Repair：
- Track tension gauge for proper track adjustments.
- Grease gun for applying grease to critical points.
- Bearing pullers for removing bearings.
- Pipe wrenches and filter wrenches for changing filters.
25、Troubleshooting Common Excavator Issues：
Despite regular maintenance, excavators may encounter problems that require troubleshooting and repair. Here are some common issues and their potential causes:
- Leaks can occur due to damaged seals, hoses, or fittings. Inspect the hydraulic system for visible leaks and replace any faulty components.
- This issue can be caused by low hydraulic fluid levels, a worn-out pump, or a clogged filter. Check the fluid levels and replace filters if necessary. If the problem persists, consult a professional.
- Inspect the wiring and connectors for any signs of damage, corrosion, or loose connections. Repair or replace the damaged components.
- Ensure the battery terminals are clean and securely connected. If the battery is old or not holding a charge, consider replacing it.
- Engine Issues
- This could be due to a weak battery, a faulty starter motor, or fuel delivery problems. Check the battery, starter motor, and fuel system for any issues.
- Insufficient coolant, a malfunctioning radiator, or a faulty thermostat can cause the engine to overheat. Check the coolant levels and inspect the cooling system for any leaks or blockages.
