When trading old diesel engines, how do you identify the advantages and disadvantages? According to the theory and practical experience, one can ask, two to see, three tests, test-based identification method. Ask the old diesel engine's purchase time, use, and the reason for the current sale. Ask the past repairs, which major parts have been replaced, and ask what the problem is in use so that there is a more comprehensive understanding of the old diesel engine. Second, look at the signs and appearance of old diesel engines. To see which factory it produced, when it was delivered, how long it was from now; see if the paint on the outside was falling off, if there was any defect, if the model was eliminated. From the signage and appearance to determine the old and new diesel engine. Trial test machine. The old diesel engine is carefully checked by cranking the crankshaft, pulling the flywheel, and starting the machine. The specific inspection steps are: Shake the crankshaft so that the fuel injectors are supplied with oil. If the nozzle emits a crisp sound, it indicates that the performance of the fuel injector and the plunger pair is still good; if there is no abnormal noise such as “in the wheel roomâ€, the wear of the gear is not serious. 2. Pull the flywheel up and down, if there is no sound, indicating that the gap between the shaft of the crankshaft spindle and the bearing shell is not large. 3. Turn the flywheel so that the piston approaches the bottom dead center, and then shake the flywheel left and right. If there is no “click†sound, the wear between the stem and the bush of the connecting rod is not serious. 4. The cylinder is depressurized and the crankshaft is cranked. When the decompression is removed, if the repulsive force of the piston is large, the flywheel rapidly turns, indicating that the wear of the cylinder, the piston and the piston ring is small. When cranking the crankshaft, the pointer of the oil pressure gauge should not be lower than 1 or the oil marking red mark can rise quickly, and the pressure of the hand should be laborious. 5. Start the machine. If it is easy to start, the exhaust smoke is colorless or light gray, and the rotation speed is stable and noiseless, indicating that the technical condition of the old diesel engine is good. Through the above methods for the identification of the old diesel engine, it is generally possible to distinguish the old and new levels and advantages and disadvantages. This makes the price of the old diesel engine more accurate.