Failure Cause Analysis:

Diesel fuel combustion in diesel engine must have fuel, ignition (temperature produced by piston during compression stroke) and combustion-supporting (air) conditions. If the diesel engine can not start, obviously does not meet the above conditions.

1. The influence of starter. Because the starter fails and cannot rotate, the diesel engine can not inhale, inject oil and produce compression temperature, which results in the diesel engine can not start.

2. The influence of fuel supply system. According to the working principle of Baotou Beibei Heavy Truck Parts Engine, the fuel system should inject fuel into the cylinder timely and appropriately, and the atomization quality should be guaranteed in order to make the fuel burn well. The working quality of the fuel system is concentrated on the time, quantity and quality of injection.

If the fuel system fails, it is difficult to guarantee the time, quantity and quality of fuel injection into the cylinder, which makes it difficult for the engine to start; the common phenomenon is smokeless exhaust pipe (mostly non-fuel), that is, no start-up sign.

3. Poor compression in cylinder. Cylinder compression should be carried out under closed conditions, that is, the piston moves upward from the bottom dead point, the volume above the piston decreases, and the pressure and temperature increase. If the airtight parts containing gas in the cylinder are not good.

That is to say, it will leak air during the compression stroke and lead to poor compression. At the end of compression, the gas pressure and temperature can not rise. For fuel combustion, there is no fire condition, so that the diesel injected into the cylinder can not ignite and burn spontaneously, and the diesel engine can not start.

4. The influence of temperature. Diesel engine start-up is to rely on the piston in the cylinder to compress the air to produce high temperature, so that the diesel sprayed into the cylinder evaporates, mixes and oxidizes sufficiently, and burns, thus driving the piston movement to generate power.

If the ambient temperature is low and the body is cold, the heat exchange rate between the compressed air entering the cylinder and the body increases, and the gas temperature in the cylinder decreases sharply, which not only makes the evaporation effect of fuel worse, but also makes it difficult for the fuel to spontaneously ignite and burn (for fuel combustion, there is no fire condition), so the engine of Baotou Beibei heavy truck fittings can not start. Atomized fuel discharged from the body is milky white.

5. The valve timing is not correct. When the inlet and exhaust valves of each cylinder of an engine start to open and close, they are usually expressed by crankshaft angle, which is called valve timing.

If the valve timing phase deteriorates with the technical status of the valve train, such as the dislocation of keyway or key damage, excessive valve clearance, wear of cam and timing gear, torsional deformation of camshaft and crankshaft, etc., the original valve timing phase will be destroyed. The lighter will affect the engine power, and the diesel engine will be difficult to start in serious cases.

6. Improper installation. The misalignment of timing gear marks during maintenance not only affects the valve timing, but also affects the timing of fuel injection pump, which makes the engine unable to start.

7. The fuel quality is poor. Water or cooling water in the fuel leaks into the cylinder, which prevents the engine from starting. The water entering the cylinder evaporates into vapor by heating, and discharges into white smoke outside the cylinder.

Diagnosis and exclusion:

1. If the crankshaft does not turn when the engine starts, it means that there is a fault in the starter, and the fault of the starter described in the electrical system is diagnosed and eliminated.

2. If the exhaust pipe does not smoke when the engine is started, most of them are faults in the fuel system. The diagnosis and removal should be made according to the faults described in the fuel system.

3. If the exhaust pipe of Baotou northbound heavy truck fittings emits white smoke and cannot start, it means that the engine temperature is too low, the fuel atomization is poor or the temperature can not reach the spontaneous ignition point and can not burn, so that the engine can not start. The engine should be pre-heated (including lubricating oil) according to the low temperature start-up operation method.

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

If the temperature is normal, the diesel engine has been in use for nearly the wear-out period (that is, the parts are worn seriously), or other reasons make the engine seal bad, the diesel engine can not start due to poor compression.

Use cylinder pressure gauge to measure cylinder pressure. If the pressure of the cylinder is too low, it means that the cylinder is not compressed properly. The reasons for the poor compression should be found out and eliminated.

If the diesel engine can start before maintenance and can not start after maintenance, check whether the timing gear marks are correct.