Komatsu pc121-6 is a second-hand imported machine with one cylinder and one cover. Generally, it costs about 411,111 yuan in Shenzhen market. It is suggested to recruit a knowledgeable person to search for a 3-hand excavator in the market. Generally, sh121－a1/a2/A2 is between 221,111 and 281,111 yuan, and the color is already very good. It should be noted that there is little difference between sh111 and sh121, so it should be carefully distinguished. There are three kinds of Komatsu pc121-6, and the price difference of each kind is very big. You can look at the computer and monitor to tell.

3. the difference between sh121 and sh111 is that sh121 has a supercharger and a slightly longer arm. Komatsu single-time, two ecus are the earliest, Komatsu dual-time large LCD integrated ecu is environmentally friendly, this machine is regarded as the second generation at-6, Komatsu dual-time small LCD integrated ecu, and the generator is the last generation of-6 with one cylinder and one cover, and then it will be-7.

4. first, look at the appearance, whether there is no big bump or fracture, whether there is original paint, whether there is serious oil leakage in various parts during walking, etc., and then try to start the car, whether the cold car starts well, whether the instrument and electrical computer work normally, whether the engine speed drops when it is loaded, whether the exhaust smoke is large or not, whether the car is blocked during operation, whether the speed of rotating walking is much worse than normal, etc., which depends on the test driver. Look at the oil leakage of each part after the test. As for the wear and tear in the shovel mentioned by the above person, it can be replaced. Now a bucket is only four or five thousand. I have bought several machines for your reference. That is, seven points of experience and three points of luck. May you buy a good car! 6. Beginners' learning: Solving common circuit faults of Hitachi -2/3 engine:

1. First, check the resistance of two solenoid valves, and then switch two high-speed solenoid valves when there is no problem. If you check the solenoid valves, one solenoid valve must be damaged or blocked.

Solution: clean them first, and it is useless to replace them.

2. Check if the engine is still stuck. Check whether the d2111 control tube inside the computer is damaged. If it is damaged, check whether the circuit is short-circuited.

Solution: Replace the d2111 and deal with the short-circuited part. 3. Observe whether the indicator light of the pvc computer flashes normally (whether it is on or off is abnormal). If it is on, 91% of it is that the central processor of the main computer is damaged and does not light. Check whether the resistance of the 11 ohm 4 watt of the main computer is open. If there is no open circuit and the resistance is seriously hot, please check the 5v peripheral circuit.

Solution: Check the a/p/dp sensor, in which the A sensor is more likely to be damaged. 4. If the computer, solenoid valve and a/p/dp sensor are normal and the car is still stuck, remove the ec computer or disconnect the communication connection between ec and pvc. If it is normal, check whether the speed sensor or related lines are damaged. Solution: replace the speed sensor or check the sensor circuit

8.[quote][b] The following is a quote from an entertainment excavator at 15: 44: 11 on March 24, 2116: [/b]

1. The operation technology must first confirm the surrounding conditions. During rotary operation, be aware of the surrounding obstacles and terrain and operate safely; When working, it is necessary to confirm the front and rear direction of the crawler to avoid overturning or bumping; Try not to face the final drive in the digging direction, otherwise it will easily damage the walking motor or hose; When working, it is necessary to ensure that the left and right tracks are in complete contact with the ground to improve the dynamic stability of the whole machine. 2. Effective excavation method When the bucket cylinder and the connecting rod, the bucket cylinder and the bucket arm form 91 degrees with each other, the excavation force is the largest; When the bucket teeth keep an angle of 31 degrees with the ground, the excavation force is the best, that is, the soil cutting resistance is the smallest; When digging with a stick, ensure that the angle of the stick is between 45 degrees from the front and 31 degrees from the back. Using the boom and bucket at the same time can improve the excavation efficiency. 3. Digging rocks Using a bucket to dig rocks will cause great damage to the machine and should be avoided as much as possible; When it is necessary to dig, the position of the machine body should be adjusted according to the crack direction of the rock, so that the bucket can be shoveled smoothly for digging; Insert the bucket teeth into the rock cracks, and dig with the digging force of the bucket arm and bucket (pay attention to the slippage of the bucket teeth); Rock that has not been broken should be broken before digging with a bucket. 4. When leveling the slope, the machine should be laid flat on the ground to prevent the body from shaking. It is very important to grasp the coordination of the action of the boom and the bucket arm and control the speed of the boom and the bucket arm for plane trimming. 5. The loading machine body should be in a horizontal stable position, otherwise it is difficult to accurately control the rotary unloading, thus prolonging the operation cycle time; Keep a proper distance between the machine body and the truck to prevent the tail of the machine body from colliding with the truck when making a 1.81-degree rotation; As far as possible, carry out the left rotary mounting, so as to broaden the field of vision and improve the operation efficiency, and at the same time, correctly grasp the rotation angle to reduce the time for rotation; The truck position forest is lower than that of the excavator to shorten the boom lifting time and have a good line of sight; Loading sand and gravel first, and then placing big stones, can reduce the impact on the trunk. 6. When working in soft areas or in water, you should know the degree of soil looseness, and pay attention to limit the digging scope of the bucket to prevent accidents such as landslides and landslides and deep car body subsidence. When working in water, pay attention to the allowable water depth range of the car body (the water surface should be below the center of the carrier chain wheel); If the water level is high, the inside of the slewing bearing will be poorly lubricated due to the entry of water, the engine fan blades will be damaged due to the impact of water, and the electrical circuit elements will be short-circuited or open-circuited due to the entry of water. 7. Hoisting operation: When the hydraulic excavator carries out hoisting operation, it should confirm the surrounding conditions of the hoisting site, use high-strength hanging hooks and wire ropes, and try to use special hoisting devices when hoisting; The operation mode should be micro-operation mode, and the action should be slow and balanced; If the length of the lifting rope is appropriate, too long will make the hanging object swing greatly and it is difficult to control it accurately; Adjust the position of the bucket correctly to prevent the steel wire rope from slipping; Construction personnel should try not to get close to the lifting objects to prevent danger due to improper operation. 8. Steady operation method When working, the stability of the machine can not only improve the work efficiency and prolong the life of the machine, but also ensure the safety of operation (put the machine on a flat ground); The stability of the driving sprocket on the rear side is better than that on the front side, and the final drive can be prevented from being hit by external force; The track's wheelbase on the ground is always greater than the track pitch, so the forward working stability is good, and lateral operation should be avoided as far as possible; Keep the digging point close to the machine to improve the stability and excavator; If the excavation point is far away from the machine, the operation will be unstable because the center of gravity moves forward; The stability of lateral excavation is worse than that of forward excavation. If the excavation point is far away from the center of the machine body, the machine will be more unstable. Therefore, the excavation point should keep a proper distance from the center of the machine body to make the operation balanced and efficient. 9, it is worth noting that the operating hydraulic cylinder is equipped with a buffer device, which can gradually release back pressure near the end of the stroke; If the piston is subjected to an impact load after reaching the end of the stroke, it will directly hit the cylinder head or cylinder bottom, which is likely to cause an accident, so try to leave a clearance when reaching the end of the stroke. Bulldozing operation with rotary motion will cause abnormal stress on bucket and working device, resulting in distortion or weld cracking, or even pin shaft breaking, so this operation should be avoided as far as possible. Using the weight of the machine body to excavate will cause abnormal stress state of the slewing bearing, and at the same time, it will produce strong vibration and impact on the chassis, so the application of hydraulic cylinder or hydraulic pipeline will cause great damage. When loading and unloading heavy materials such as rocks, they should be unloaded near the bottom of the truck compartment, or the soil should be loaded first, and then the rocks should be loaded. Unloading at high altitude is prohibited to reduce the impact damage to the truck. When the track is deeply immersed in the mud, put a board under the bucket, use the bottom of the bucket to support the track, and then put a board under the track to drive the machine out. 11, the correct walking operation excavator walking, should try to put away the working device and close to the center of the body, in order to maintain stability; Put the final drive behind to protect the final drive. Avoid passing through obstacles such as stumps and rocks as much as possible to prevent the track from twisting; If it is necessary to drive over an obstacle, make sure that the center of the track is on the obstacle. When crossing the mound, always support the chassis with the working device to prevent the car body from shaking violently or even tipping over. Avoid idling the engine on a steep slope for a long time, otherwise it will lead to poor lubrication due to the change of oil level angle. Long-distance walking of the machine will cause high temperature in the roller and final drive due to long-time rotation, and the viscosity of the oil will decrease and lubrication will be poor. Therefore, it is necessary to stop the machine frequently to cool down and prolong the life of the lower body. It is forbidden to dig by the driving force of walking, otherwise the excessive load will lead to the early wear or damage of the final drive, crawler and other get-off parts. When walking uphill, the driving wheel should be behind to increase the adhesion of the track that touches the ground. When walking downhill, the driving wheel should be in front, so that the upper track can be tightened, so as to prevent the car body from slipping forward under the action of gravity and causing danger when parking. When walking on the slope, the working device should be placed in front to ensure safety. After stopping, gently insert the bucket into the ground and put a stop under the crawler. When walking and turning on steep slopes, you should slow down, turn the left crawler backwards when turning left, and turn the right crawler backwards when turning right, which can reduce the danger when turning on slopes. 11, the correct crushing operation must first put the hammer vertically on the object to be crushed. When starting the crushing operation, lift the front car body about 5cm. When crushing, the crushing head should always be pressed on the broken objects, and the crushing operation should be stopped immediately after the unbreakable objects have been crushed. When crushing, the direction of the hammer will gradually change due to vibration, so the bucket cylinder should be adjusted at any time to make the direction of the hammer perpendicular to the surface of the crushed object. When the hammer can't hit the broken object, the broken position should be changed; Don't break it for more than a minute in the next place, otherwise not only the hammer will be damaged, but also the oil temperature will rise abnormally; For hard objects, they should be gradually broken from the edge. It is forbidden to break while turning, twist after inserting the hammer head, use hydraulic hammer horizontally or upward, and use hydraulic hammer as a chisel.

The purpose of regular maintenance of excavators is to reduce machine failures and prolong the service life of the machines; Shorten the downtime of the machine; Improve work efficiency and reduce operating costs. As long as the fuel, lubricating oil, water and air are well managed, 71% of failures can be reduced. In fact, about 71% of failures are caused by poor management. 1, fuel management should choose different brands of diesel according to different environmental temperatures; Diesel oil cannot be mixed with impurities, lime soil and water, otherwise the fuel pump will be worn prematurely; The high content of paraffin and sulfur in inferior fuel will damage the engine; After daily operation, the fuel tank should be filled with fuel to prevent water droplets from forming on the inner wall of the fuel tank; Open the drain valve at the bottom of the fuel tank to drain water before daily operation; After the engine fuel is used up or the filter element is replaced, the air in the road must be exhausted. 2. Management of other oils Other oils include engine oil, hydraulic oil, gear oil, etc. Different brands and grades of oil cannot be mixed; Different kinds of excavator oil have different chemical or physical additives in the production process; Ensure that the oil is clean and prevent impurities (water, dust, particles, etc.) from mixing; Select the oil label according to the ambient temperature and use. When the ambient temperature is high, the engine oil with high viscosity should be selected, and when the ambient temperature is low, the oil with low viscosity should be selected; The viscosity of gear oil is relatively large to adapt to large transmission load, and the viscosity of hydraulic oil is relatively small to reduce the flow resistance of liquid. 3. Lubricating grease management Using lubricating oil (butter) can reduce the wear of moving surfaces and prevent noise. When storing grease, dust, sand, water and other impurities should not be mixed; It is recommended to choose lithium-based grease g2-l1, which has good wear resistance and is suitable for heavy-duty working conditions. When filling, try to squeeze out all the old oil and wipe it clean to prevent sand from sticking. 4. Maintenance of the filter element The filter element plays the role of filtering impurities in the oil or gas path to prevent them from invading the system and causing failures; All kinds of filter elements should be replaced regularly according to the requirements of the operation and maintenance manual; When replacing the filter element, check whether there is metal attached to the old filter element, and diagnose and take improvement measures in time if metal particles are found; Use pure filter elements that meet the requirements of the machine. The filtering ability of fake and inferior filter elements is poor, and the quality of the filter layer and materials do not meet the requirements, which will seriously affect the normal use of the machine. 5. Contents of regular maintenance ① The fuel filter and additional fuel filter should be replaced after the new machine works for 251h; Check the clearance of the engine valve. ② Daily maintenance; Check, clean or replace the air filter element; Clean the inside of the cooling system; Check and tighten the track shoe bolts; Check and adjust the back tension of the track; Check the air inlet heater; Replace the bucket teeth; Adjust the bucket clearance; Check the front window cleaning fluid level; Check and adjust the air conditioner; Clean the floor in the cab; Replace the crusher filter element (optional). When cleaning the inside of the cooling system, after the engine is fully cooled, slowly loosen the water filler cap to release the internal pressure of the water tank, and then drain the water; Don't clean the engine while it is working, the high-speed rotating fan will cause danger; When cleaning or replacing coolant, the machine should be parked on a level ground; Replace the coolant and corrosion inhibitor according to Table 3. The ratio of antifreeze to water is as required in Table 4. ③ Check items before starting the engine. Check the level of coolant (add water); Check the engine oil level and add oil; Check the fuel level (add fuel); Check the hydraulic oil level (add hydraulic oil); Check whether the air filter element is blocked; Check the wires; Check whether the horn is normal; Check the lubrication of the bucket; Check the water and sediment in the oil-water separator. ④ Every 111 maintenance items. Pin shaft of cylinder head of boom cylinder; Boom pin; Rod end of boom cylinder; Pin shaft of bucket cylinder head; Connecting pin of boom and bucket arm; Cylinder rod end of bucket rod cylinder; Bucket cylinder head pin shaft; Half-bar connecting rod connecting pin; Rod end of bucket rod and bucket cylinder; Bucket cylinder head pin shaft; Connecting pin of stick connecting rod; Check the oil level in the slewing mechanism box (add oil); Drain water and sediment from the fuel tank. ⑤ Maintenance items every 251h h. Check the oil level in the final drive box (add gear oil); Check the battery electrolyte; Replace the oil in the engine oil pan and the engine filter; Lubricate the slewing bearing (2 places); Check the tension of the fan belt, and check the tension of the air conditioner compressor belt and make adjustments. ⑥ Maintenance items every 511h. At the same time every 111 and 251h maintenance projects; Replace the fuel filter element; Check the height of the grease for the slewing pinion (add grease); Check and clean radiator fins, oil cooler fins and cold sensor fins; Replace the hydraulic oil filter element; Replace the oil in the final drive box (only at 511h for the first time and at 1111h thereafter); Clean the air filter elements inside and outside the air conditioner system; Replace the hydraulic oil vent element. ⑦ Maintenance items every 1111h. At the same time every 111, 251 and 511h maintenance projects; Replace the oil in the slewing mechanism box; Check the oil level of the shock absorber housing (