FARMERS CAN IDENTIFY OLD DIESEL ENGINES BY USING THE FOLLOWING METHODS WHEN PURCHASING THEM, AND GENERALLY OBTAIN SATISFACTORY DIESEL ENGINES.1. ROTATE THE CRANKSHAFT TO SUPPLY OIL TO THE FUEL PUMP. IF THE FUEL INJECTOR EMITS A LIGHT AND BRITTLE INJECTION SOUND, IT INDICATES THAT THE PERFORMANCE OF THE PLUNGER AND FUEL INJECTOR IS STILL GOOD. IF THERE IS NO ABNORMAL SOUND IN THE GEAR CHAMBER, IT INDICATES THAT THE WEAR OF THE GEAR IS NOT SEVERE.2. SHAKE THE FLYWHEEL UP AND DOWN, IF THERE IS NO SOUND OR OBVIOUS SHAKING, IT INDICATES THAT THE GAP BETWEEN THE CRANKSHAFT MAIN JOURNAL AND THE BEARING SHELL IS NOT LARGE; IF THERE IS NO "CLICK" SOUND WHEN ROTATING THE FLYWHEEL, IT INDICATES THAT THE WEAR BETWEEN THE CRANKSHAFT CONNECTING ROD JOURNAL AND THE CONNECTING ROD BEARING IS NOT SEVERE.3. REDUCE THE PRESSURE OF THE CYLINDER AND ROTATE THE CRANKSHAFT. WHEN THE PRESSURE IS RELEASED, IF THE REBOUND FORCE OF THE PISTON IS LARGE AND THE FLYWHEEL ROTATES QUICKLY, IT INDICATES THAT THE WEAR OF THE CYLINDER LINER, PISTON, AND PISTON RING IS RELATIVELY SMALL. THIS IS BECAUSE THE OIL PRESSURE GAUGE READING SHOULD NOT BE LESS THAN 1MPA OR THE RED OIL PRESSURE INDICATOR FLOAT CAN BE QUICKLY LIFTED, AND MANUAL PRESSURE ON THE FLOAT SHOULD BE LABORIOUS.4. IT IS RELATIVELY EASY TO START A DIESEL ENGINE, WITH COLORLESS OR LIGHT GRAY EXHAUST, STABLE SPEED, AND NO NOISE, INDICATING THAT THE TECHNICAL CONDITION OF THE DIESEL ENGINE IS GOOD.