1, Why can't I increase the throttle when the diesel engine of the loader is just started?
After the diesel engine of the loader is just started, it should run at low speed for 3-5 minutes, with the purpose of:
1. Warm up: Slowly and evenly heat up all parts of the body to reach normal operating temperature, reduce wear and tear, and avoid mechanical strain.
2. Ensure lubrication: When the diesel engine is first started, the viscosity of the lubricating oil is high, and the lubrication of various components is poor. After warming up, gradually let the lubricating oil reach each lubrication part to avoid dry friction and damage to the mating surface.
3. After the diesel engine is just started, the machine temperature is low and the diesel combustion is incomplete. At this point, if the throttle is increased and the fuel supply is increased, excess unburned diesel will form carbon deposits, which will exacerbate diesel engine emissions. In addition, excess diesel may also flow into the crankcase along the cylinder wall, affecting cylinder wall lubrication and diluting the oil in the oil pan, reducing lubrication performance and shortening the service life of the diesel engine.
For diesel engines equipped with exhaust gas turbochargers, it is even more important to pay attention to warming up the car. If the throttle is immediately increased after starting, the speed of the turbine will increase, but the oil will not reach the surface of each lubrication part in time, which will not form good lubrication and easily cause the turbine shaft to get stuck, resulting in a malfunction.
2, What are the reasons for sudden shutdown of loader diesel engines and how should they be handled?
When the diesel engine suddenly shuts down on its own during operation, do not immediately restart the diesel engine. Carefully analyze and inspect the cause of the sudden shutdown of the diesel engine, repair it, and then restart it for operation.
The main reasons for the sudden shutdown of the diesel engine of a loader shovel are:
1. Sudden shutdown caused by oil supply system malfunction. This shutdown phenomenon is caused by air entering the diesel engine fuel supply circuit or fuel supply interruption. Before the diesel engine suddenly shuts down, the speed fluctuates and the operation is unstable. The reasons for fuel supply interruption include:
a. Insufficient fuel in the diesel tank, sufficient fuel should be added;
b. The oil circuit is not tightly sealed. When such a malfunction occurs, it can be determined by venting the fuel system after shutdown. If a large number of foam like oil bubbles are released at the vent screw by pumping oil with the hand oil pump, the shutdown is caused by oil and gas in the oil. The sealing of the low-pressure oil circuit should be carefully checked.
c. The camshaft of the fuel injection pump is broken or the rolling key is broken, and the connecting plate is broken. The fuel injection pump should be inspected.
2. Sudden shutdown caused by crankshaft lock up
After stopping the machine, observe whether there is any abnormality in the water temperature and whether there is water in the oil pan (the engine oil is emulsified). If the inspection is normal, the diesel engine crankshaft should be rotated. If it feels difficult or unable to rotate, it can be judged as burning the bearing or locking the crankshaft after burning the bearing.
After the failure of burning the bearing shell, the cause should be identified, the oil passage should be cleaned, the crankshaft should be ground, the bearing shell and a few components (such as connecting rods) should be replaced before assembling and testing the machine.
3. Sudden shutdown caused by cylinder pulling
3, What are the main reasons for early wear and tear of loader diesel engines?
Early wear of a diesel engine refers to the phenomenon where the power of the engine decreases significantly and fuel consumption increases due to the wear of the main moving pairs (such as piston rings, crankshaft, bearing shells, cylinder liners, etc.) during a relatively short period of use, resulting in the engine being unable to continue operating effectively. The early wear of diesel engines is mainly due to the following reasons:
① The new machine runs at high load without running in;
② Air filter failure;
③ Improper use and maintenance, poor oil quality;
④ Poor combustion leads to excessive carbon buildup in the cylinder.
4, What is the cause of cylinder liner strain on a loader? How to prevent it?
The main manifestations of cylinder liner strain are: knocking sound of the piston inside the cylinder, decreased power of the diesel engine, and blue or white smoke emission from engine oil combustion; Oil becomes thinner, pressure drops, etc.
The reasons for cylinder failure include:
① The cooling system has malfunctioned, causing the machine to overheat and the piston to expand excessively after being heated.
② Insufficient oil volume, deterioration, or impurities in the engine oil can cause poor lubrication.
③ The clearance between the piston and the cylinder wall is too small (often seen in new or recently overhauled diesel engines).
④ The piston ring is broken or stuck.
⑤ The failure of the piston pin retaining spring causes the piston pin to move.
5, What are the measures to reduce the wear of loader cylinder liners?
To reduce cylinder liner wear, in addition to taking anti-corrosion and wear-resistant measures in design and manufacturing, the following points should also be noted in use and maintenance engineering:
⑴ Correct starting and starting
After starting the cold car, it should be warmed up for 3-5 minutes with a low throttle before starting the vehicle. At the beginning of operation, it should work at a low load for a period of time, and then work at a high load after the temperature rises.
⑵ Maintain the normal temperature of the engine
The temperature of the diesel engine is too low to maintain good lubrication, which will increase the friction of the cylinder wall; If the temperature is too high, it will reduce the strength of the cylinder and aggravate wear, and may even cause the piston to expand excessively, resulting in a "cylinder pulling" accident. The normal working temperature of a diesel engine is 80 ℃~90 ℃. When the temperature exceeds 95 ℃, the load should be reduced or the cooling should be stopped.
⑶ Maintain good lubrication
Regularly check and maintain good oil quality, moderate oil level, regularly replace and select oil with appropriate viscosity according to the season to ensure good lubrication.
Strengthen the maintenance work of the "three filters" (air filter, oil filter, and diesel filter)
This is the main measure to prevent mechanical impurities from entering the cylinder, reduce cylinder wall wear, and extend engine service life, which is particularly important for diesel engines used in loaders that are often exposed to high dust content.
⑸ Improve maintenance, repair, and quality
Strictly follow the technical standards specified in the diesel engine maintenance manual for maintenance and repair operations. Adjust and control the clearance between each fitting (opening clearance) to prevent accelerated wear between the piston and cylinder wall due to improper maintenance and repair.
6, What are the reasons for frequent flushing of cylinder liners in loader diesel engines?
The cylinder gasket burned by high-temperature gas inside the cylinder is called a "flushing gasket", also known as a "burning gasket".
After flushing the cylinder gasket of a diesel engine, abnormal phenomena such as water tank "bubbling", water ingress into the oil pan, oil emulsification, and exhaust pipe drainage (emitting white smoke) usually occur. The main reasons for the flushing gasket are
⑴ Cylinder head deformation
Due to the long-term alternating effects of high temperature and high pressure gases, the cylinder head undergoes thermal deformation; Improper disassembly (not in order) can also cause deformation. After the deformation of the cylinder head, the raised part cannot press the cylinder gasket tightly, causing high-temperature gas leakage and burning of the cylinder gasket.
⑵ The uneven height of the cylinder liner boss causes some cylinders to have poor sealing.
In order to ensure that the cylinder liner and gasket are tightly pressed onto the cylinder block and maintain good sealing, it is generally required that the surface of the cylinder liner protrusion be higher than the cylinder block by a certain size (usually 0.05-0.12mm). There are also regulations on the difference in protrusion of the cylinder liner for the same diesel engine (or two cylinders under the same cylinder head) (usually 0.05mm).
If the specified value is exceeded, it may cause insufficient sealing pressure, resulting in high-pressure and high-temperature gas escaping and damaging the cylinder gasket.
⑶ Loose cylinder head bolts or insufficient tightening torque
When the diesel engine leaves the factory, the manufacturer provides clear requirements for the torque of the cylinder head fastening bolts in the use and maintenance manual. During maintenance, the cylinder head should be tightened strictly according to the prescribed time and method.
The assembly method of the cylinder gasket is incorrect or the quality of the cylinder gasket is poor.
⑸ Poor machine operation, overheating causing cylinder gasket flushing.
7, What are the reasons for the high oil level in the oil pan of a loader diesel engine? How to exclude it?
The rise in oil level in the diesel engine oil pan is caused by diesel or water entering the oil pan. Some diesel engines without crankshaft rear frame oil seals have raised oil levels, which may also be due to hydraulic transmission oil entering the oil pan.
Entering diesel into engine oil can reduce its viscosity, cause the oil to deteriorate, and prevent the formation of an oil film on the surfaces of relative motion, leading to increased wear. If water enters the engine oil, it will emulsify the oil and lose its lubricating effect.
Therefore, once the oil level in the oil pan rises, the machine should be stopped for inspection, troubleshooting, and oil replacement before operation. The main reasons for the increase in oil level in the oil pan are:
1. A certain cylinder (or several cylinders) of the diesel engine is not working or working poorly
Due to the stuck needle valve of the fuel injector in the open state or low injection pressure, poor atomization is caused, which prevents the diesel injected into the cylinder from completely forming a mixture and burning, and flows into the oil pan from the piston ring, cylinder liner, and piston side, causing the oil level in the oil pan to rise. Can it be used in this situation? Cut off cylinder method? Find which cylinder or cylinders are not working or working poorly, identify the fault and eliminate it. If necessary, the fuel injector can be verified.
2. Water ingress into the oil pan causes the oil level to rise
After water enters the oil pan, the engine oil will emulsify. The main reasons for water ingress into the oil pan are:
① The cylinder gasket is burnt and leaking. At this time, when checking the water tank, it will be found that there are "bubbling" and "boiling" phenomena inside the tank, and the cylinder gasket should be checked and replaced;
② The cylinder liner cracks, causing cooling water to seep into the cylinder and flow into the oil pan. The cylinder liner should be replaced. In this situation, there may also be a phenomenon of the water tank "bubbling" and "boiling". Especially in winter, the phenomenon of cylinder cracking is more common due to "extreme cold";
③ The water blocking ring of the cylinder liner is malfunctioning and leaking, and should be replaced. Does the water tank leak in this situation? Flipping: phenomenon.
3. Some diesel engines, due to damage to the crankshaft rear oil seal (or not the skeleton oil seal), if the torque converter leaks oil severely, hydraulic transmission oil may leak into the oil pan, causing the oil level to rise. At this point, there is no diesel odor or emulsification in the engine oil, and the torque converter should be inspected.
8, Why is there oil in the water tank of a loader diesel engine?
When checking the water level of the diesel engine radiator (water tank), if the problem is found in the water tank and the fault is eliminated before starting the diesel engine, there are two situations that can cause oil in the water tank:
1. The diesel engine oil cooler (water cooler) has frozen and cracked, the water cooler core has cracked, and the sealing gasket (ring) is damaged, causing oil to leak into the cooling system and enter the water tank. The oil cooler should be opened for inspection. If there is a malfunction of the oil cooler freezing and cracking, it is usually accompanied by low oil pressure.
2. The hydraulic transmission oil-water cooler has poor sealing or freeze-thaw, resulting in oil in the water tank. The hydraulic transmission oil-water cooler should be disassembled and inspected.
In order to prevent the phenomenon of water cooler freezing and cracking, when using a diesel engine in cold seasons, do not forget to drain the water in the diesel engine oil cooler and the hydraulic transmission oil-water cooler.
9, What are the methods to extend the service life of diesel engine oil for loaders?
1. Regularly maintain the oil filter;
2. Prevent fuel from entering the diesel engine oil pan;
3. Keep the diesel engine oil pan and valve cover relatively closed to prevent debris from entering the engine oil;
4. Select the appropriate grade of engine oil as required;
5. Regularly change the engine oil according to regulations. When changing the engine oil, the engine oil should be drained while it is still hot after shutdown, and the oil pan should be thoroughly cleaned to prevent residual waste engine oil from mixing with new engine oil and causing corrosion to the new engine oil.
6. Maintain the normal operating temperature of the diesel engine, which is between 80 ℃ and 90 ℃. If the temperature is too high, the engine oil will become thinner, accelerate the oxidation and deterioration of the engine oil, and reduce the lubricating effect of the engine oil. If the temperature is too low, diesel will not be fully burned, and some of the oil and gas will condense into liquid and flow into the oil pan along the cylinder wall, diluting the engine oil.
10, What are the reasons for the loader diesel engine traveling car?
When a diesel engine is running, the periodic changes in speed between high and low over a large range are called "traveling wheels".
The phenomenon of "drifting" is diverse, sometimes it occurs when the accelerator pedal drifts at a certain position, sometimes it occurs when idling, and sometimes it occurs when downstream at a certain load.
The essence of a traveling car is that the normal speed regulation function of the diesel engine is disrupted, usually due to excessive resistance from the fuel injection pump components (such as racks) or moving parts inside the governor, which reduces the sensitivity of the governor and causes the traveling car to move; Excessive clearance between internal components of the fuel injection pump or governor may cause a delay in the change of fuel supply compared to the change in speed, which may also result in traveling; The phenomenon of drifting may also be caused by oil circuit faults, mainly including:
1. Low pressure oil circuit blockage leads to poor fuel supply, disrupting the continuity of fuel supply;
2. Oil supply circuit intake;
3. Poor atomization or jamming of the fuel injector results in uneven operation of each cylinder and drifting.
When checking the cause of the malfunction of the traveling block, the oil circuit fault should be checked first. If there is no fault in the oil circuit, then the fuel injection pump governor should be inspected and the fuel injection pump should be verified.
It should be noted that during idle driving, in addition to the above reasons, there are also the following factors related:
a. The poor low-speed operation of the fuel injector is mainly due to wear or poor manufacturing quality, which causes it to not atomize or drip oil at low speeds, while working normally at medium and high speeds.
b. The idle fuel supply of the fuel injection pump is insufficient. After increasing the idle fuel level, the traveling block disappears;
c. Improper adjustment of the idle limit screw may cause idle travel, and the idle limit screw should be adjusted.
