1. Why can't the accelerator be increased when the loader forklift diesel engine has just started?
After the electric loaders forklift diesel engine is just started, it should run at low speed for 3~5 minutes, the purpose of which is to:
(1) Warm-up: Let all parts of the body heat up slowly and evenly to reach the normal working temperature, reduce wear and tear, and avoid mechanical strain;
(2) Ensure lubrication: when the diesel engine is just started, the viscosity of the lubricating oil is large, and the lubrication of each component is poor, so that the lubricating oil gradually reaches the lubrication parts after warm-up, so as to avoid dry friction and damage to the mating surface;
(3) After the diesel engine is just started, the temperature of the machine is low, and the diesel combustion is incomplete. At this time, if the throttle is increased and the fuel supply is increased, the excess unburned diesel will form carbon deposits, which will aggravate the emissions of the diesel engine. In addition, excess diesel fuel may flow into the crankcase along the cylinder wall, affecting cylinder wall lubrication and diluting the oil pan, reducing lubrication performance and reducing the life of the diesel engine.
For diesel engines equipped with exhaust gas turbochargers, more attention should be paid to warming the car.
If the throttle is increased immediately after starting, the speed of the turbine will increase, and the oil will not have time to reach the surface of each lubrication part, and the shape will not be well lubricated, and it is easy to produce the phenomenon of the turbine shaft being stuck, resulting in failure.
2. What are the reasons for the sudden shutdown of the loader, forklift, and diesel engine, and how should it be handled?
When the diesel engine suddenly stops when it is working, do not start the diesel engine again immediately, but carefully analyze and inspect the reasons for the sudden shutdown of the diesel engine, and then start the operation after repair.
The main reasons for the sudden shutdown of loader, forklift, diesel engine, are:
(1) Sudden shutdown due to failure of the oil supply system. This shutdown phenomenon is caused by the incoming air in the oil supply circuit of the diesel engine or the interruption of the oil supply. Before the diesel engine suddenly stops, the speed is up and down, and the work is not stable. The reasons for the interruption of the oil supply are:
a. If the diesel tank is insufficient, the fuel should be filled up;
b. The oil circuit is not tightly sealed. In the event of such a failure, it can be judged by the method of deflating the fuel system after the shutdown. If a large amount of foamy oil bubbles are released at the vent screw by pumping oil with a hand oil pump, it is caused by oil and gas in the oil. The tightness of the low-pressure oil circuit should be carefully checked.
C. If the camshaft of the fuel injection pump is broken or the key is rolled and the connecting plate is broken, the fuel injection pump should be overhauled.
(2) Sudden shutdown due to crankshaft locking
After the shutdown, observe for anomalies in the water temperature and for water in the oil pan (the oil is emulsified). If the inspection is normal, the diesel engine crankshaft should be rotated, if you feel that the rotation is hard or can not rotate, it can be judged that the crankshaft is locked after burning the bearing or burning the bearing.
After the failure of burning bearings, the cause should be found, the oil channel should be cleaned, the crankshaft should be grinded, and the bearings and a few parts (connecting rods, etc.) should be replaced before the test machine can be assembled.
(3) Sudden shutdown caused by pulling cylinders
3. What are the main reasons for the early wear and tear of loader forklift diesel engine?
The early wear of diesel engine refers to the phenomenon that the diesel engine can not continue to work effectively due to the wear and tear of the main moving pairs (such as piston rings, crankshafts, bearings, cylinder liners, etc.) in a short service time. The early wear of diesel engines is mainly due to the following reasons:
(1) The new machine runs under heavy load without running-in;
(2) The air filter fails;
(3) Improper use and maintenance, poor oil quality;
(4) Poor combustion, so that the cylinder has too much carbon.
4. What is the cause of cylinder liner strain of loader forklift? How can it be prevented?
The main manifestations of cylinder liner strain are: knocking sound of the piston in the cylinder;
Diesel engine power decreases; The engine oil burns, and the exhaust smoke is blue or white; The oil becomes thinner, the pressure drops, etc.
(1) The reasons for the failure of the pull cylinder are:
(1) The cooling system is faulty, the machine is overheated, and the piston expands too much after heating;
(2) The oil quantity is insufficient, deteriorated or contains impurities, resulting in poor lubrication;
(3) The gap between the piston and the cylinder wall is too small (mostly seen in new or overhauled diesel engines)
(4) The piston ring is broken or stuck;
(5) The piston pin circlip fails, causing the piston pin to move.
5. What are the measures to reduce the wear of the cylinder liner of the loader forklift?
To reduce the wear of cylinder liners, in addition to anti-corrosion and wear-resistant measures in design and manufacturing, the following points should be paid attention to in the use and maintenance engineering:
(1) Start and start correctly
After the cold car starts, it should warm up the car for 3~5 minutes under the small throttle state before starting the car, and when it is running at first, it should work with a small load for a period of time, and then work with a large load after the temperature rises.
(2) Maintain the normal temperature of the engine
The temperature of the diesel engine is too low and cannot maintain good lubrication, which will increase the friction of the cylinder wall; If the temperature is too high, the strength of the cylinder will be reduced and the wear will be aggravated, and the piston may even be over-inflated and cause a "cylinder" accident, the normal working temperature of the diesel engine is 80 C ~ 90 C. When it exceeds 95C, the load should be reduced or shut down for cooling.
(3) Maintain good lubrication
Always check and maintain good oil quality and proper oil level, change it regularly and use the right viscosity oil according to the season to ensure good lubrication.
(4) Strengthen the maintenance 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 the life of the engine, which is especially important for loader diesel engines that are often in high dust content.
(5) Improve maintenance and quality
Maintenance and repair operations are carried out in strict accordance with the technical standards specified in the diesel engine use and maintenance manual. Adjust and control the mating clearance (opening clearance) to prevent the wear between the piston and the cylinder wall from being accelerated due to improper repair and maintenance.
6. What are the reasons why the loader, forklift, and diesel engine often flush the cylinder gasket?
The cylinder gasket is burned by the high-temperature gas in the cylinder, which is called "cylinder gasket", also known as "cylinder gasket".
After the diesel engine flushes the cylinder gasket, there will generally be abnormal phenomena such as "bubble" of the water tank, water ingress of the oil pan, emulsification of the engine oil, and exhaust pipe drainage (white smoke). The main reasons for the flush gasket are:
(1) The cylinder head is deformed
Due to the long-term thermal deformation of the cylinder head by the alternating action of high temperature and high pressure gas; Improper disassembly (not in order) can also cause deformation. After the cylinder head is deformed, the upturned part cannot be pressed tightly and the head gasket is not tightened, resulting in high-temperature gas leakage and burn the head gasket.
(2) The height of the cylinder liner boss is different, resulting in the poor sealing of individual cylinders.
In order to make the cylinder liner and cylinder gasket pressed on the cylinder block and maintain good sealing, it is generally required that the cylinder liner end face boss plane is higher than the cylinder block of a certain size (generally 0.05~0.12mm), and the difference in the protrusion of the cylinder liner of the same diesel engine (or two cylinders under the same cylinder head) is also specified (generally 0.05mm).
If the specified value is exceeded, it may cause insufficient sealing pressure, which will cause high-pressure and high-temperature gas to escape and break the cylinder gasket.
(3) The cylinder head bolt is loose or the tightening torque is insufficient
When the diesel engine leaves the factory, the torque of the cylinder head fastening bolt is clearly required in the operation and maintenance manual provided by the manufacturer, and the cylinder head should be tightened in strict accordance with the specified time and method during maintenance.
(4) Incorrect assembly method of the cylinder head gasket or poor quality of the cylinder head gasket.
(5) The machine is not working well, and the cylinder gasket is caused by overheating.
7. What are the reasons for the increase in the oil level of the loader forklift diesel engine oil pan? How to exclude?
The elevated oil level of the diesel engine oil pan is caused by the ingress of diesel fuel or water into the oil pan. Some diesel engines without the crankshaft rear skeleton oil seal are elevated, which may also be due to the entry of hydraulic transmission oil into the oil pan.
The diesel oil enters the oil, which will reduce the viscosity of the engine oil and deteriorate the engine oil, resulting in the formation of an oil film on the relative moving surfaces and the aggravation of wear; Water ingress into the oil will emulsify the oil and lose its lubrication effect.
Therefore, once the oil pan oil level is found to rise, it should be stopped for inspection, troubleshooting, and oil change before operation. The main reasons for the increase in the oil pan oil level are:
(1) A cylinder (or cylinders) of the diesel engine does not work or works poorly
Fogging is caused by the injector needle valve stuck in the open state or the injection pressure is low
Poor chemical performance, so that the diesel injected into the cylinder can not completely form a mixture and burn, and from the piston ring, cylinder liner and piston side into the oil pan, so that the oil pan oil level rises. In this case, the " cylinder breaking method" can be used to find out which cylinder or which cylinders are not working or working poorly, find out the fault and eliminate it. If necessary, the injector can be inspected.
(ii) The oil pan is flooded and the oil level is raised
When the oil pan is flooded, the oil will emulsify. The main causes of water ingress into the oil pan are:
(1) Cylinder head gasket burns out and leaks. At this time, check the water tank, you will find that there is a phenomenon of "bubble" and "boiling" in the water tank, and the cylinder gasket should be checked and replaced;
(2) The cylinder liner is cracked, so that the cooling water penetrates into the cylinder and flows into the oil pan, and the cylinder liner should be replaced. In this case, the phenomenon of "boiling" and "boiling" of the water tank will also occur. Especially in winter, due to "quenching", the phenomenon of cylinder cracking is more common;
(3) The cylinder liner water-blocking ring fails and leaks, and the water-blocking ring should be replaced. In this case, the water leaks, and the tank does not have a ? Bubble: phenomenon.
(3) For some diesel engines, due to damage to the oil seal at the rear of the crankshaft (or not the skeleton oil seal), if the torque converter leaks seriously, the hydraulic transmission oil will leak into the oil pan, which will raise the oil level. At this time, there is no diesel smell in the oil, and it is not emulsified, and the torque converter should be overhauled.
8. Why is there oil in the water tank of loader, forklift, diesel engine?
When checking the water level of the diesel engine radiator (water tank), if the cause is found in the water tank, the diesel engine is started after troubleshooting, and there are two situations that can make the oil in the water tank:
(1) The diesel engine oil cooler (water cooler) freezes and cracks, the core of the water cooler is cracked and the gasket (ring) is damaged, so that the oil leaks into the cooling system, resulting in oil entering the water tank, and the oil cooler should be opened for inspection. If there is a failure of the oil cooler freezing and cracking, it is generally accompanied by the phenomenon of low organic oil pressure.
(2) If the hydraulic transmission oil-water cooler is poorly sealed or frozen and cracked, resulting in oil in the water tank, the hydraulic transmission oil-water cooler should be disassembled and inspected.
In order to prevent the water cooler from freezing and cracking, when using a diesel engine in the cold season, you must not forget to drain the water in the diesel engine oil cooler and the hydraulic transmission oil water cooler.
9. What are the ways to extend the service life of diesel engine oil for loader forklifts?
(1) Maintain the oil filter on time;
(2) Prevent fuel from entering the diesel engine oil pan;
(3) Keep the diesel oil pan and valve cover relatively closed to prevent debris from invading the oil;
(4) Select the appropriate grade of engine oil as required;
(5) Change the engine oil regularly according to the regulations, and when changing the engine oil, the oil should be drained while it is hot after the shutdown, and the oil pan should be thoroughly cleaned to prevent the residual waste engine oil from mixing with the new engine oil and corrosive to the new engine oil.
(6) Maintain the normal working temperature of the diesel engine, the normal working temperature of the diesel engine is 80C~90C, the temperature is too high to thin the oil, accelerate the oxidation and deterioration of the oil, and reduce the lubrication of the oil. If the temperature is too low, the diesel will not be fully combusted, and a part of the oil and gas will condense into a liquid state and flow down the cylinder wall into the oil pan, diluting the oil.
10. What are the reasons for loaders, forklifts, diesel engines, and traveling vehicles?
When the diesel engine is running, the periodic change of high and low speed in a wide range is called "traveling car".
There are various phenomena of "traveling", sometimes the accelerator pedal is traveling in a certain position, sometimes it is traveling at idle, and sometimes it is traveling at a certain load.
The essence of the traveling car is that the normal speed regulation function of the diesel engine is destroyed, usually the fuel injection pump parts (such as racks) or the moving parts in the governor have excessive resistance, so that the sensitivity of the governor decreases and causes the traveling car; The matching gap of the internal parts of the fuel injection pump or governor is too large, so that the change of fuel supply lags behind the excessive change of speed, which may also cause the traveling car; The phenomenon of traveling can also be caused by oil circuit failure, mainly including:
(1) The low-pressure oil circuit is blocked, and the oil supply is not smooth, which destroys the continuity of the oil supply;
(2) Air intake of oil supply circuit;
(3) Poor atomization or jamming of the injector, which makes the cylinders work unevenly and travels.
When checking the cause of the fault of the traveling car, you should first check the fault of the oil circuit, and if the oil circuit is not faulty, then go to overhaul the governor of the fuel injection pump and check the fuel injection pump.
It should be noted that in addition to the above reasons, the following factors are related to the idling of the car:
a. The injector works poorly at low speed, mainly because the injector is worn or poor manufacturing quality, which causes it to not atomize or drip at low speed, but works normally at medium and high speed.
b. The idle fuel supply of the fuel injection pump is insufficient, and the idle fuel volume is increased, and the traveling car disappears;
c. If the idle speed limit screw is not properly adjusted, resulting in idle travel, the idle speed limit screw should be adjusted.
11. What are the reasons for the "boiling" of the loader forklift diesel engine? How to eliminate and prevent?
"Boiling" refers to the phenomenon that the temperature of the diesel engine is too high, and the coolant is boiling and steaming in the water tank. The main reasons for the "boiling" of diesel engine, prevention and elimination methods are:
(1). The inner wall of the radiator heat pipe (core) is too thick, which affects the heat dissipation. Attention should be paid to adding clean cooling water during use; and regularly remove limescale from the tank;
(2). Water leakage from the radiator or cooling system, resulting in insufficient coolant. Check the cause of water leakage, add enough cooling water after troubleshooting;
(3). The cylinder gasket or cylinder liner is damaged, and the high-pressure gas in the cylinder enters the water cooling system, resulting in the water tank "boiling" and "boiling" (in this case, more
accompanied by emulsification of diesel engine oil). The cylinder gasket or cylinder liner should be inspected for damage, and replaced if necessary;
(4). The water pump is damaged, the cooling water is not circulating or the circulation strength is insufficient. The cause of the damage to the pump should be checked, and if necessary, the new pump should be replaced;
(5) The machine works for a long time with high load, the fan belt is too loose, the wind speed is not strong, and the phenomenon of boiling due to overheating will also occur. The operating load of the loader should be reasonably arranged to prevent the machine from overheating.
(6). The thermostat is damaged, resulting in the large circulation not being opened, causing the machine to overheat, and the thermostat should be replaced.
It should be noted that loaders working in alpine areas will also have the phenomenon of boiling, the main reason is that the radiator freezes and the coolant cannot be circulated. Therefore, when using a loader in alpine areas, attention should be paid to adding a thermal insulation device at the front end of the radiator.
12. What are the reasons for the black smoke from the exhaust of the diesel engine of the loader forklift? How to exclude?
When the diesel engine is working under load, the exhaust smoke color is generally light gray. It is normal for a diesel engine to emit black smoke from the exhaust when it is overloaded, accelerates suddenly, climbs or works under heavy load. However, if the black smoke is emitted under no load or small load or the black smoke is too heavy under heavy load, it is an abnormal phenomenon, and the causes and elimination methods are as follows:
(1) If the air filter is blocked, causing the cylinder to be inflated insufficiently, the air filter element should be cleaned or replaced;
(2) If the supercharger is faulty, the air supply pressure is insufficient, and the diesel engine is not completely combusted, and the supercharger should be overhauled;
Suggested reading:(3) If the injector is poorly atomized or has oil dripping, the injector should be overhauled and inspected, and the fuel injection head (needle valve couple) should be replaced if necessary;
(4) Improper adjustment of oil supply time, there are the following two types:
a. Black smoke comes out of the exhaust pipe, and at the same time, there is a crisp knocking sound in the cylinder, and the work is rough. This phenomenon is generally caused by the premature oil supply time. Feeding oil too early can often also cause starting difficulties.
b. Black smoke from the exhaust pipe, while there is a flame in the muffler, and the sound is dull. This phenomenon is caused by the late supply of oil. If the oil supply time is too late, it often causes the diesel engine to overheat, the exhaust temperature rises, and even the parts may be burned out.
In addition, the diesel engine with the automatic advance of the oil supply angle emits black smoke at high speed, which may also be caused by the damage of the automatic advance of the oil supply angle, and the automatic advance of the oil supply angle should be disassembled and checked. If the oil supply time is improper, it can be checked and adjusted according to the above methods.
(5) The oil supply of each cylinder is uneven
The exhaust pipe emits black smoke, and at the same time, the machine vibrates seriously, and there is too much oil for individual cylinders, which can be checked and eliminated by the "cylinder breaking method";
(vi) Poor quality of diesel
The diesel fuel is of poor quality, causing poor atomization, so that it cannot be burned completely, the fuel tank should be cleaned and the diesel fuel replaced.
13. What are the causes and elimination methods of white smoke from the exhaust pipe of the loader forklift?
There is water in diesel or water in the cylinder liner, and the water is discharged from the exhaust pipe as steam, that is, white smoke is emitted. The main causes of white smoke from diesel engines and the elimination methods are:
(1) If there is water mixed in the diesel fuel, check whether the diesel fuel is mixed with water;
(2) Improper adjustment of the advance angle of oil supply
When the advance angle of fuel supply is too small and the temperature of the diesel engine is not high, a part of the fuel will be discharged with the exhaust gas before combustion, and the discharged oil mist will form white gas. When the heat engine is under heavy load, the temperature of the combustion chamber and exhaust pipe rises, and the diesel fuel that cannot be completely burned in the combustion chamber continues to decompose in the exhaust pipe, and black smoke will be discharged. It should be checked whether the oil supply time is appropriate.
(3) Poor atomization of the injector
If the injector is not well sealed, the atomization is poor or even there is oil dripping, and the oil entering the cylinder will not have time to mix and burn, and white smoke will be discharged. If the injector drips heavily or multiple injectors drip oil, the diesel fuel will also escape into the oil pan and dilute the oil. The injector should be inspected, and the needle valve coupling should be replaced if necessary.
(4) Water ingress into the cylinder liner
The cylinder gasket is damaged, and the connecting water channel or cylinder liner is cracked, so that the cooling water continuously penetrates into the cylinder, and when exhausting, the hot air flow is evaporated or washed away, forming water mist or water vapor, which is discharged as white smoke. At this time, if you put white paper on the exhaust pipe mouth, it will be sprayed with fine water droplets. The cause of the water leak should be checked.
It should be noted that when the diesel engine is running in the cold engine, the exhaust pipe constantly emits white smoke. This is more common during the cold winter months when diesel engines are used. This is because the temperature in the cylinder of the diesel engine is low, and the evaporation of oil and gas on the cylinder wall is discharged with the exhaust pipe, and the exhaust pipe also enters the moisture after the shutdown, and the white water vapor is discharged, which is a normal phenomenon. However, if white smoke still emits after the heat is warmed, it is a fault.
14. What are the causes and elimination methods of blue smoke from the exhaust pipe of the loader forklift?
Blue smoke from the exhaust pipe is a characteristic of burning engine oil, and the main causes and elimination methods are:
(1) The oil level is too high. The oil level should be checked and the oil should be filled according to the regulations.
(2) The piston ring and the cylinder liner are too large or the piston ring is in the opposite direction. The cylinder pressure should be checked, and if the cylinder pressure is too low, the piston ring should be dismantled and checked. If necessary, reassemble the quadruple or replace the piston ring.
(3) The gap between the valve stem and the valve guide is too large or the valve oil seal is damaged. Valve seals and valve fit clearances should be checked, and valve seals or valve guides should be replaced if necessary.
(4) The supercharger is damaged and leaks. In this case, the diesel engine suddenly emits blue smoke, and the supercharger should be overhauled or the supercharger oil seal ring should be replaced.
15. What are the abnormal noises of loader forklift diesel engine? What causes it?
Diesel engines in good technical condition can hear a uniform and slight exhaust sound when idling; When running at high speeds, it is a smooth roar. If the sound increases, accompanied by a decrease in power, an increase in fuel consumption, and an increase in vibration, it can be judged as an abnormal sound.
When the engine has abnormal noise, the type and possible cause of the sound can be judged according to the different technical conditions, the different sounds emitted, the different working conditions and spatial positions of each matching pair, the parts and sound characteristics of the sound, and the timing and change rules of the sound.
Nowadays, the method of diagnosing abnormal noise mainly depends on human feeling, based on experience. Although some new diagnostic instruments have emerged, they are not widely used. Common squeaks and squeaks and diagnostic methods are as follows:
(i) Valve knocking
There is a crisp metal knocking sound in the cylinder head cover area, and when the diesel engine is changing at medium and low speeds, the knocking sound is more obvious and crisp. There are rules
The "click, click" sound of the rhythm is mainly caused by excessive valve clearance. When the temperature of the diesel engine rises or is tested by the "cylinder breaking" method, the sound does not change. When the diesel engine is running at high speed, the knocking sound is not obvious due to the loud noise of other machinery.
The main reasons for excessive valve clearance are: loose valve adjustment screws, which makes the screws exit or the moving parts of the valve mechanism (such as cams, tappets, rocker arms, etc.) are worn. When the valve clearance is too large, the diesel engine will be underinflated due to insufficient intake or exhaust, resulting in a decrease in power and an increase in fuel consumption, etc., and the valve clearance should be adjusted in time.
(2) Piston pinning
The main reason for the piston pin ringing is that the piston pin, connecting rod bushing, or piston pin seat hole is worn, resulting in excessive mating clearance, and the piston pin makes a sound when it hits during movement.
The characteristics of piston pin sound are: when switching from idle speed to medium speed operation, the sound is more obvious; The cycle (frequency) of the sound varies with the rise and fall of the engine speed
Change. When the injection time is brought forward, the sound is more pronounced and clearer. When the engine temperature rises, the sound generally does not weaken, and sometimes it is significantly stronger. The test was carried out by the " cylinder breaking method", and the sound was weakened or disappeared.
(3) The piston knocks on the cylinder
The common and main reason for the piston knocking sound is that the piston and the cylinder wall are worn, and the matching clearance exceeds a certain limit, and the piston swings in the process of moving up and down, knocking on the cylinder wall and making a sound of dang and . Sometimes, although the mating clearance is not exceeded, it will sound if the connecting rod is bent and deformed.
The piston knocking sound is obvious when the temperature of the diesel engine is low, and it is especially clear when idling. As the temperature rises, the sound decreases or disappears. This is characteristic of the piston knocking cylinder.
Due to the similarity between the knocking sound and the piston pin ringing, in order to facilitate the distinction,
A small amount of oil can be injected into the top of the piston from the injector seat hole, and the diesel engine can be started again after turning the crankshaft several times. If the sound disappears at the moment after starting, it is the sound of knocking on the cylinder. It should be noted that when the oil supply is advanced (within the specified range), it will also cause a slight knocking sound, which is normal.
(4) Connecting rod bearings
The main reason for the sound of connecting rod bearings is the wear of the journal and the bearing, the burning of the bearing alloy layer, the falling off, the loosening of the bearing cover (pad cover), the rotation of the bearing (the outer circle of the bearing), and the sound of the moment of work hitting each other.
The characteristics of the connecting rod bearing sound are: the sound is obvious at medium speed, not obvious due to the increase of other mechanical noise at high speed, and the sound is weakened at idle. When the temperature of the diesel engine changes, the sound does not change. In the medium speed range, when accelerating and decelerating, the sound will become louder with the increase of speed.
(5) Crankshaft bearing ringing
The reason for the ringing of the crankshaft bearing is the same as that of the connecting rod bearing, and its characteristics are: the sound is duller than that of the knocking cylinder, piston pin and connecting rod bearing. When refueling or decelerating suddenly, the sound is clearly clear; If the bearing alloy layer is burned out and falls off, the diesel engine will shake. When working under heavy loads, the sound is obvious and clear. The sound does not change when the engine temperature changes.
When the bearing sounds, the single cylinder "broken cylinder" test, the sound has no obvious change; In the "broken cylinder" test of two adjacent cylinders, the sound will be reduced or disappeared. In addition, it can also be judged by touching the bearings of the external body of the diesel engine with a metal rod or a screwdriver with a wooden handle.
Note: If the noise is caused by too large a gap between the bearing and the journal, the oil pressure will drop significantly.
(6) Camshaft bearings
The most common and main reason for the sound of camshaft bearings is the wear of camshafts and bearings (bushings) and the excessive clearance of fits; The bearing alloy layer is burned out, falling off, or the outer diameter of the bearing and the housing bore bearing "go out of the circle". The camshaft bearing sound is a choppy rhythmic dull "click, click" sound that is noticeable at medium speed and can also be heard at idle. In the engine temperature change or ? cylinder breakage test, the sound does not change.
It can be seen that the abnormal noise of diesel engines is mostly related to improper adjustment of coordination clearance and poor lubrication. Therefore, the machine in operation should be regularly checked for fit clearance and good lubrication. For the diesel engine with abnormal noise, it should be eliminated in time before use, so as to prevent aggravation of wear and tear and mechanical accidents.
16. What are the reasons for the breakage of the diesel high-pressure oil pipe of the loader forklift? How can I prevent it?
The fracture of diesel high-pressure oil pipe is mainly caused by the internal stress generated during assembly and the bending fatigue damage caused by high-frequency vibration. The main reasons are:
(1) Improper position or loosening of high-pressure tubing clamps
When the natural frequency of high-pressure tubing vibration is the same as that of the diesel engine, it will cause the high-pressure tubing to produce resonance, and a large vibration will occur and fatigue fracture occurs in the middle or both ends of the high-pressure tubing.
(2) In the process of repair and assembly, the tubing is forcibly bent, which causes stress in the high-pressure tubing at the sharp bend, and fatigue fracture occurs due to periodic vibration during oil injection; The external wear of the tubing or the internal cracks during manufacturing, due to the high working pressure (generally about 20Mpa) in use, cause the tubing to break due to cracks.
17. What are the reasons for the high oil temperature of the torque converter of the loader forklift? How to exclude?
The normal oil temperature of the torque converter is 70C~110C, and the maximum can not exceed 120C. If the loader is operating under non-long-term heavy load conditions, and the torque converter temperature rises rapidly and exceeds 120C, it is an abnormality. Note that the reason i.e. the exclusion method is:
(1) If the oil level of the gearbox is too low or too high, the oil level of the hydraulic transmission oil should be checked and the oil level should be adjusted to the specified oil level. The inspection method is: the Skid Steer loader runs for about 5 minutes, and the oil can be released from the oil drain switch on the gearbox. If too much oil is released, too much oil should be filled, and the oil should be partially released; If no oil is released, the oil level is too low, and hydraulic transmission oil should be filled.
(2) The transmission pump is damaged or the pressure of the transmission control valve is low, which causes the transmission clutch to slip and heat up the oil. If the variable speed pump is damaged, the variable speed pressure cannot be adjusted, and the pump body is heated or abnormal noise, the variable speed pump should be replaced; If the pressure of the variable speed control valve is low, check and adjust the pressure to the specified value.
(3) The hydraulic transmission oil deteriorates and should be replaced with new oil.
If the loader works continuously under heavy load for too long, the torque converter oil temperature gauge should be observed at any time, and once it exceeds 110C, the load operation should be reduced or shut down for cooling.
18. The reasons and elimination methods for the low oil pressure of all gears of loader forklift loader gearbox?
The normal working pressure range of the gearbox is 1.08~1.47Mpa, and the pressure is lower than 1.08Mpa, but higher than 0.9Mpa, the pressure is too low. The main reasons for the low pressure of the gearbox and the elimination method are:
(1) If the oil quantity of the gearbox oil pan is insufficient, the hydraulic transmission oil should be filled to the specified oil level;
(2) If the oil filter of the gearbox is blocked, the cause of the blockage should be checked, and the oil filter should be cleaned or replaced;
(3) If the oil suction pipeline from the oil pan of the gearbox to the transmission pump is poorly sealed, the pipeline should be overhauled or replaced;
(4) The variable speed pump should be replaced if the wear and tear is serious, resulting in internal leakage;
(5) If the regulator valve of the variable speed control valve is improperly adjusted or the regulator spring is damaged, check whether the regulator spring is damaged and readjust it to the specified value;
(6) The regulator stem or accumulator piston of the variable speed control valve is stuck in the valve body. The regulator and accumulator should be disassembled for cleaning.
It should be noted that oil deterioration will also cause the phenomenon of low oil pressure, and the oil quality should be checked and replaced in time; Inaccurate pressure gauge or damaged sensor will also cause the illusion of low pressure, which should be repaired and replaced in time.
19. What are the reasons for the low oil pressure of a certain gear of the loader forklift loader and the elimination method?
In this case, the general variable speed pump and variable speed control valve are working normally, and the fault is in a certain gear itself. There are several scenarios:
(1) The pressure of the 1st and 2nd gears is normal, and the reverse pressure is low, which is due to the damage of the piston oil seal (piston ring) of the reverse clutch or the cracking of the box. The reverse cylinder of the box should be checked for cracks, and then the oil seal should be checked for damage. The cause of cracks in reverse cylinders is generally due to high system pressure.
(2) The pressure of the first gear and reverse gear is normal, and the pressure of the second gear is low. The main reason is that the rotating oil seal at the junction of the shaft end of the 2-speed assembly and the end cover of the gearbox is damaged, or
The oil seal on the joint surface of the end cover and the box body is damaged; The piston seal inside the 2nd gear clutch is damaged. The 2nd gear should be disassembled, the rotary oil seal and related seals should be overhauled, and replaced if necessary.
(3) The pressure of reverse gear and 2nd gear is normal, and the pressure of 1st gear is low. This is due to damage to the sealing ring at the junction of the 1st gear clutch assembly and the gearbox or damage to the piston sealing ring (piston ring) in the 1st gear clutch of the gearbox, the oil seal at the junction of the 1st gear clutch and the box should be checked for damage, and the 1st gear clutch cylinder should be disassembled, and if necessary, the sealing ring should be replaced.
20. What is the reason for a large amount of foam in the hydraulic transmission oil of the loader forklift gearbox and the weakness of the loader?
There are a lot of bubbles in the hydraulic transmission oil in the gearbox, because the oil suction hose joint between the transmission oil pan and the transmission pump is not tightened or the hose is damaged.
21. Why does the braking phenomenon suddenly occur in the process of changing 1st gear to 2nd gear or 2nd gear to 1st gear?
If the lever system parts (shift lever, etc.) of the variable speed control valve are loose or improperly adjusted, the pressure oil enters the first gear and the second gear at the same time (that is, the oil of the second gear is not broken) when changing gears, resulting in the interference phenomenon between the first gear and the second gear, and the loader will not move in this case and brake.
22. The newly repaired gearbox of the loader forklift, the pressure of each gear is normal and there is no abnormal sound, but there is only reverse gear, and there is no reason for the first and second gears?
This kind of failure occurs in the newly repaired gearbox, mostly because the reverse clutch does not separate, because the reverse clutch friction plate is installed too much or wrong. The number of pieces or the assembly position and sequence of the reverse clutch friction plates should be checked. This failure can also occur in 1st gear and is handled in the same way as in reverse gear.
23. Why does the main reducer of the loader forklift drive axle have a toothing phenomenon?
In addition to the improper quality of the spiral bevel tooth meshing pair and the improper adjustment clearance, the incorrect operation is the main reason. Under normal circumstances, the loader is driven at the same time as the front and rear axles during operation. If it is overloaded, the rear axle is off the ground, and the entire load is borne by the front axle, the main reducer of the front axle is easily damaged. If the bucket entry angle is too large, the boom is too low, it is easy to produce the front axle off the ground during operation, and the whole load is borne by the rear axle, and it is easy to cause damage to the rear axle main reducer at this time. The final reducer is damaged, which is mostly manifested as abnormal sound due to broken teeth.
24. When the loader forklift loader walks, it does not go when it appears, that is, the cold car does not go, and the hot car does not go, why?
(1) The cleanliness of the working oil is poor, and the dirt is sucked around the filter screen and gradually blocks the filter screen, and the dirt is dispersed when stopping.
(2) The transmission pump is worn, the oil is thick when the car is cold, and the internal leakage is small, which can meet the needs of each gear, while the oil is thin when the car is hot, the internal leakage is large, and the insufficient oil supply cannot meet the needs of each gear, resulting in the inability to walk normally. (3) The oil suction hose of the variable speed pump is blistered due to the aging of the inner layer, and the hose is flattened and blocked when the car is hot, resulting in insufficient oil supply, and the oil suction pipeline returns to normal when the car is cold.
25. The loader forklift gearbox pressure is normal, the I. gear and reverse gear can not walk, only the II. gear can drive normally, why?
The reason for this failure is that the I. gear in the gearbox, the reverse gear connecting disc is torsioned or the connecting bolt is broken, etc., resulting in the power can not be transmitted, so the I. gear and reverse gear can not walk; The II. gear is directly connected with the spline in the sun gear, and the power can be directly output, so the II. gear can be driven.
26. When the loader forklift loader is operating, why is the bucket unable to lift and flip?
When the loader is working, the boom lifting in the hydraulic system is weak (slow speed) or the bucket is unable to flip over, mainly for the following reasons:
(1) When the diesel engine is working, the speed does not rise high. When the boom and bucket reversing valve spool valve are in the neutral position, press the engine accelerator pedal to the end, if the diesel engine speed does not reach the rated speed, it may be a diesel engine failure, and the reason for the low speed of the diesel engine should be checked.
(2) When the throttle is small, the boom is lifted slowly (or the boom cannot be lifted), the bucket is weak, and it works normally when the throttle is increased. The reasons for this failure are as follows:
a. If the working pump is badly worn or damaged, the working pump should be replaced.
b. The opening pressure of the first-arrival safety valve is too low or the sealing is not tight. The pressure gauge should be used to measure the pressure of the working hydraulic system, if the pressure is too low and cannot be adjusted blindly, the safety valve should be removed first, and the pilot valve spring should be checked whether it is broken, whether the seal is good, and whether the main valve core is stuck. Then adjust it according to the situation.
c. Cylinder leakage caused by damage to the piston seal ring of the hydraulic cylinder or wear of the cylinder barrel (with pull marks). To judge whether the oil cylinder is leaking, the oil cylinder can be retracted to the end, and then loosen the rodless cavity oil pipe, so that the rod cavity continues to be filled with oil, if there is a large amount of hydraulic oil coming out of the rodless cavity, it means that the oil cylinder is leaking, and the oil cylinder should be overhauled.
(3) It works normally when the throttle is small, but it is weak when the throttle is large
In this case, it is mostly caused by the leakage of the low-pressure oil circuit of the working hydraulic system, and the sealing of the low-pressure oil circuit should be checked:
a. The oil level of the hydraulic oil tank is too low, which makes the working pump empty and causes insufficient oil absorption;
b. Poor sealing of the inlet pipe of the working pump or aging of the hose makes the air enter the oil pipe, and the system pressure is insufficient due to the compressibility of the air.
d. Air leakage from the working pump, resulting in air entering the working hydraulic system.
In addition, the hydraulic oil grade does not meet the requirements, which may also cause the shovel to be weak, and the hydraulic oil should be replaced as required.
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