ENGINE POWER FAILURE IS A COMMON AND FREQUENT FAULT CHARACTERIZED BY A DECREASE IN ENGINE POWER, OFTEN ACCOMPANIED BY POOR SMOKE COLOR, HIGH TEMPERATURE, UNSTABLE OPERATION, AND DIFFICULTY STARTING. THE MAIN CAUSES OF POWER FAILURE IN DIESEL ENGINES AND THEIR TROUBLESHOOTING METHODS ARE AS FOLLOWS.1. INSUFFICIENT OR UNEVEN FUEL SUPPLYREASON: BLOCKAGE OF THE FUEL TANK VENT, COLLAPSE AND BLOCKAGE OF THE FUEL PIPE, TWISTING AND BENDING OF THE HOSE, BLOCKAGE OF THE FUEL PUMP INLET FILTER SCREEN, AND BLOCKAGE OF THE DIESEL FILTER ELEMENT; OIL PIPE RUPTURE, LOOSE JOINTS, AND INADEQUATE SEALING OF GASKETS LEADING TO OIL LEAKAGE AND AIR INTAKE; THERE IS WATER IN THE FUEL; POOR OPERATION OF THE FUEL PUMP AND INSUFFICIENT FUEL SUPPLY; POOR OPERATION OF FUEL INJECTION PUMP, INSUFFICIENT OR UNEVEN FUEL SUPPLY; THE LIMIT OF THE FUEL SUPPLY ROD IS NOT ADJUSTED PROPERLY.EXCLUSION METHOD: CHECK ONE BY ONE IN THE ORDER OF "FROM OUTSIDE TO INSIDE" ALONG THE OIL CIRCUIT. CHECK FOR OIL LEAKAGE, INTAKE, AND BLOCKAGE, AS WELL AS THE PRESENCE OF WATER, THROUGH THE MANUAL OIL PUMP'S OIL PUMPING STATUS. IF THERE IS WATER IN THE OIL, THE EXHAUST PIPE WILL EMIT WHITE SMOKE AND THE ENGINE WILL NOT RUN STEADILY. IF ALL THE ABOVE FAULT FACTORS HAVE BEEN ELIMINATED AND THE FAULT STILL EXISTS IN THE LOW-PRESSURE OIL CIRCUIT, THE FUEL PUMP NEEDS TO BE INSPECTED. IF THE FAULT IS NOT IN THE LOW-PRESSURE OIL CIRCUIT, THE FUEL INJECTION PUMP NEEDS TO BE CHECKED. IN GENERAL, THE SIDE COVER CAN BE REMOVED TO CHECK FOR ANY JAMMING OF THE PLUNGER SPRING OR BITING OF THE PLUNGER; PULL THE CONTROL ARM BACK AND FORTH TO CHECK IF THE ADJUSTING GEAR RING IS BITING DUE TO THE TIGHT FIT WITH THE LINER, CAUSING THE THROTTLE TO NOT BE FULLY EXTENDED; CHECK IF THE LOCKING SCREW OF THE ADJUSTING GEAR RING IS LOOSE. CHECK IF THE RELEVANT FIT IS LOOSE BASED ON THE TYPE OF ADJUSTMENT ARM. ACCURATE MEASUREMENT OF FUEL INJECTION QUANTITY AND PRESSURE SHOULD BE CARRIED OUT ON A TEST BENCH, ALONG WITH NECESSARY DISASSEMBLY AND INSPECTION TO DETERMINE THE FAULT LOCATION BEFORE REPAIR.2. LOW INFLATION VOLUMEREASON: CLOGGED AIR FILTER; AIR LEAKAGE IN THE INTAKE PIPE; THE TURBOCHARGER IS NOT FUNCTIONING PROPERLY.AT BEST, WHEN INSUFFICIENT, THE EXHAUST PIPE WILL EMIT BLACK SMOKE OR BLACK GRAY SMOKE. IF CONSTRUCTION IS CARRIED OUT IN TUNNELS OR ON DUSTY CONSTRUCTION SITES, BLACK SMOKE OFTEN OCCURS DUE TO CLOGGED AIR FILTERS. TURBOCHARGERS ARE GENERALLY DAMAGED DUE TO POOR LUBRICATION.EXCLUSION METHOD: CLEAN OR REPLACE THE AIR FILTER; ELIMINATE AIR LEAKAGE IN THE INTAKE PIPE THROUGH REPAIR OR REPLACEMENT; REPAIR OR REPLACE THE TURBOCHARGER.3. POOR ATOMIZATION OF THE FUEL INJECTOR OR EVEN SOME CYLINDERS NOT SPRAYING FUELTHE ABOVE SITUATION MAY CAUSE INDIVIDUAL CYLINDERS TO MALFUNCTION OR NOT WORK, RESULTING IN DIFFICULTY STARTING AND BLACK OR WHITE SMOKE FROM THE EXHAUST PIPE.EXCLUSION METHOD: DETERMINE THE POSITION OF THE DEFECTIVE CYLINDER THROUGH THE CYLINDER CUT-OFF METHOD. ON THE PREMISE OF ELIMINATING THE FAULT OF THE FUEL INJECTION PUMP, THE FUEL INJECTOR CAN BE REMOVED AND ITS INJECTION PRESSURE, SEALING AND SPRAY QUALITY CAN BE TESTED ON THE TEST BENCH, AND IT CAN BE REPAIRED THROUGH INSPECTION.4. MISALIGNMENT OF FUEL INJECTION TIMINGREASON: IMPROPER ADJUSTMENT; THE FASTENING SCREWS OF THE FUEL INJECTION PUMP COUPLING CONNECTING PLATE ARE LOOSE OR THE CLEARANCE BETWEEN THE KEY AND THE KEYWAY IS TOO LARGE; WEAR IN ALL ASPECTS CAUSES A DECREASE IN THE FUEL INJECTION ADVANCE ANGLE.IF THE FUEL INJECTION TIMING IS TOO EARLY, IT WILL CAUSE KNOCKING SOUND IN THE CYLINDER, UNSTABLE OPERATION, AND BLACK SMOKE FROM THE EXHAUST PIPE. LATE TIMING CAN CAUSE THE ENGINE TO OVERHEAT, PRODUCE LOW KNOCKING SOUNDS, EMIT WHITE SMOKE FROM THE EXHAUST PIPE, AND MAKE STARTING DIFFICULT.EXCLUSION METHOD: RESTORE THE CLEARANCE BETWEEN THE KEY AND KEYWAY, ADJUST THE TIMING, AND TIGHTEN THE SCREWS.5. IMPROPER ADJUSTMENT OR FAILURE OF THE SPEED CONTROLLERREASON: THE SET SPEED IS TOO LOW; THE SPEED REGULATING SPRING IS TOO SOFT.THE ABOVE REASONS WILL CAUSE THE ENGINE TO RUN WEAKLY; IF THE SPEED CONTROL SPRING FAILS, THE SPEED MAY FLUCTUATE.EXCLUSION METHOD: RE ADJUST OR REPLACE THE SPEED REGULATING SPRING.6. LOW CYLINDER COMPRESSION PRESSURE AND SIGNIFICANT PRESSURE DIFFERENCE AMONG CYLINDERSREASON: IMPROPER VALVE CLEARANCE; THE VALVE AND VALVE SEAT ARE NOT TIGHTLY SEALED; THE CYLINDER IS NOT SEALED.IF THERE IS A VALVE MALFUNCTION, THE ENGINE WILL RUN WEAKLY, THE SPEED WILL BE UNSTABLE, THE EXHAUST PIPE WILL EMIT BLACK SMOKE, AND IN SEVERE CASES, IT WILL BE DIFFICULT TO START; IF THE CYLINDER IS NOT SEALED, IT IS OFTEN ACCOMPANIED BY OIL BURNING, BLUE SMOKE FROM THE EXHAUST PIPE, AND A BLOWING SOUND CAN BE HEARD FROM THE OIL FILLING PORT.EXCLUSION METHOD: CHECK AND GRIND THE VALVE, ADJUST THE VALVE CLEARANCE; MEASURE CYLINDER PRESSURE, IDENTIFY CYLINDERS THAT DO NOT MEET REQUIREMENTS, CHECK FOR DAMAGE TO CYLINDERS, PISTON RINGS, AND PISTONS, AND REPAIR OR REPLACE THEM THROUGH BORING AND GRINDING.IN ADDITION, CLOGGED EXHAUST PIPES OR MUFFLERS, EXCESSIVE CARBON BUILDUP IN THE COMBUSTION CHAMBER, POOR FUEL QUALITY, AND HIGH OIL LEVELS CAN ALL CAUSE A DECREASE IN ENGINE POWER AND PERFORMANCE.