1. OBSERVATION OF SMOKE PHENOMENON

When a diesel engine operates, opening the oil cap and observing dense smoke coming out it indicates ''smoking''. Severe downward smoke suggests significant wear on parts such as pistons, cylinder liners, and piston rings.

Opening the valve cover, if a faint blue or white smoke emerges from the valve root, it's termed as ''fog''. If there's excessive upward smoke, it indicates valve or valve seat wear or severe erosion, or even inadequate valve clearance. By observing smoke emissions, the specific valve or cylinder leaking air can be identified for timely repair.

2. CHECKING WATER TEMPERATURE AND COOLING SYSTEM

Elevated water temperatures in the diesel engine cooling system indicate excessive scaling or inefficiency in related components (thermostats, water pumps, fans).

3. EXAMINATION OF BLUE VALVE TIMING UNIDIRECTIONAL VALVE PHASE

During diesel engine operation, wear occurs on timing gears, cam surfaces, followers, and rocker arms, delaying the opening and closing time of intake and exhaust valves, deviating from optimal valve timing, and reducing charging efficiency, thereby lowering engine power. Therefore, regular inspections of the diesel engine's timing phases are necessary, and adjustments should be made promptly if found unsatisfactory.

4. COMPRESSION CHECK FOR LEAKAGE

The compression check method involves shaking the crankshaft without relieving pressure. When there is substantial compression force, applying additional upward force and holding without releasing the crank. Strong rebound indicates good compression force; otherwise, it reflects poor compression force.

5. SMOKE OBSERVATION AND INSPECTION OF SMOKE COLOR

Under normal operation, diesel engines usually do not emit smoke or release faint grayish-white smoke, sometimes barely visible to the naked eye. Black smoke indicates insufficient gas in the cylinder, leading to incomplete combustion; white smoke suggests fuel mixed with water or incomplete diesel combustion causing vaporization visible from the exhaust pipe.

6. INSPECTION OF CARBON DEPOSIT STATUS

If the exhaust outlet of a diesel engine accumulates black-gray carbon with a layer of white frost and a thin carbon layer, it indicates a healthy working status. An individual cylinder's exhaust outlet with significantly thicker carbon than others indicates a malfunctioning fuel injector or deteriorated cylinder sealing, necessitating repair or replacement. Excessive moisture or oil at specific cylinder outlets suggests oil leakage and requires repair. Thick and dark carbon layers in all cylinder outlets signal low working humidity, delayed fuel injection, or severe diesel issues, requiring proper use and timely adjustment.

7. EXAMINATION OF FIRE AND TIMING

Fire observation involves checking if fuel injection is normal, specifically if the fuel supply advance angle complies with regulations. Delayed fuel supply (insufficient advance angle) leads to difficult engine starting, incomplete combustion, smoky exhaust, and increased engine temperature, causing insufficient power. Premature fuel supply (excessive advance angle) during diesel engine operation produces detonation noises, increases the risk of damaging parts, makes starting in reverse easier, and affects diesel engine power output.

8. INSPECTION OF FUEL INJECTION AND STICKING

The fuel injection pump should not be skewed, leak oil, or produce uneven oil mist in an inadequate range. During operation, a crisp ''puff-puff'' sound should be audible, and a pulsating sensation should be felt when touching the high-pressure oil pipe. Adequate fuel injection doesn't entirely signify no issues with oil path components. Therefore, it's essential to inspect whether the fuel delivery rod and fork are stuck or loose.