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How To Eliminate The Failure Of Diesel Engine Starting

The crankshaft does not rotate when the diesel engine is started; When the diesel engine is started, the exhaust pipe does not smoke; When the diesel engine is started, the exhaust pipe emits white smoke of engine starting.

Failure Cause Analysis Of Engine Starting:

When diesel is burned in the diesel engine, it must meet the conditions of fuel, kindling (the temperature generated by the piston during the compression stroke) and combustion supporting (air). If the diesel engine cannot be started, it obviously does not meet the above conditions of engine starting.

1. Impact of starter. Because the starter fails to rotate, the diesel engine cannot inhale, inject fuel and generate compression temperature, resulting in the failure of diesel engine to start of engine starting.

How To Eliminate The Failure Of Diesel Engine Starting

2. Impact of fuel supply system. According to the working principle of the engine, the fuel system should timely and appropriately inject fuel into the cylinder and ensure the atomization quality to make the fuel burn well; The working quality of fuel system is mainly reflected in fuel injection time, fuel injection quantity and atomization quality.

If the fuel system fails, it is difficult to ensure the time, quantity and atomization quality of fuel injected into the cylinder, so it is difficult to start the engine; The common phenomenon is that the exhaust pipe is smokeless (mostly without fuel), that is, there is no sign of start-up of engine starting.

3. Poor compression in cylinder. The cylinder compression shall be carried out under closed conditions, that is, the piston moves upward from the bottom dead center, the volume above the piston decreases, and the pressure and temperature rise. If the parts containing gas in the cylinder are poorly sealed.

How To Eliminate The Failure Of Diesel Engine Starting (2)

That is, it will leak during the compression stroke, resulting in poor compression. At the end of compression, the gas pressure and temperature cannot rise. For fuel combustion, there is a lack of kindling conditions, so that the diesel injected into the cylinder cannot ignite and burn by itself, so the diesel engine cannot be started of engine starting.

4. The influence of temperature. When the diesel engine is started, the air is compressed by the piston in the cylinder to produce high temperature, so that the atomized diesel injected into the cylinder is evaporated, fully mixed and oxidized to burn, and promote the movement of the piston to generate power.

If the ambient temperature is low and the engine block is cold, the heat exchange rate between the compressed air entering the cylinder and the engine block will increase, resulting in a sharp drop in the gas temperature in the cylinder, which will not only worsen the evaporation effect of the fuel, but also make it difficult for the fuel to ignite and burn by itself (there is no kindling condition for fuel combustion), so the engine cannot be started; The fuel that fails to burn and atomize is milky white outside the engine body.

How To Eliminate The Failure Of Diesel Engine Starting (3)

5. Wrong valve timing. The time when the intake and exhaust valves of each cylinder of the engine start to open and close is usually represented by the crankshaft angle, which is called the valve timing of engine starting.

If the valve phase deteriorates with the change of the technical conditions of the valve mechanism, such as the dislocation due to the damage of the keyway or key, the excessive valve clearance, the wear of the cam and timing gear, the torsional deformation of the camshaft and crankshaft, etc., the original valve phase will be damaged. If it is light, it will affect the power of the engine, and if it is serious, it will make it difficult for the diesel engine to start.

6. Improper installation. The installation timing gear marks are not aligned during maintenance, which not only affects the valve timing, but also affects the fuel supply timing of the fuel injection pump, resulting in the failure of the engine to start.

7. Poor fuel quality. Water in the fuel or cooling water leaks into the cylinder, making the engine unable to start. The water entering the cylinder is heated and evaporated into steam, which is discharged outside the body and becomes white smoke.

How To Eliminate The Failure Of Diesel Engine Starting (4)

Diagnosis And Troubleshooting:

1. If the crankshaft does not rotate when the engine is started, it indicates that there is a fault in the starter. Diagnose and eliminate the starter fault as described in the electrical system.

2. If the exhaust pipe does not smoke when starting the engine, most of them are faults of the fuel system, diagnosis and troubleshooting shall be carried out according to the faults described in the fuel system.

3. If the exhaust pipe emits white smoke and cannot be started, it means that the engine temperature is too low, the fuel atomization is poor, or the temperature cannot reach the spontaneous combustion point, so that the engine cannot be started. It shall be started according to the operation method of low-temperature start, that is, preheating the engine (including lubricating oil).

If the air temperature is normal and the exhaust pipe still emits white smoke when the engine is started, check whether there is water in the fuel or cooling water leaking into the cylinder.

How To Eliminate The Failure Of Diesel Engine Starting (5)

If the air temperature is normal, the diesel engine is close to the wear and tear period (i.e. serious wear of parts), or the engine seal is poor due to other reasons, and the diesel engine cannot be started due to poor compression.

 

Use the cylinder pressure gauge to measure the cylinder pressure. If the cylinder pressure is too low, it means that the cylinder has poor compression. Find out the cause of poor compression and eliminate it.

If the diesel engine starts before maintenance and cannot be started after maintenance, check whether the timing gear mark is aligned.

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