(1) There is air or water in the fuel system. If the oil pipe interface is loose or the oil inlet pipe is damaged by friction, the air will enter the fuel system. At the same time, the diesel contains a certain amount of water. When there is more air and water, the normal starting of the diesel engine will be affected.
(2) There is no oil in the oil tank or the oil inlet switch is not opened or the vent hole of the oil tank cover is blocked. Some drivers do not pay attention to the diesel content in the fuel tank. When the diesel is used up, it cannot be added in time, or the fuel inlet switch of the fuel tank is manually closed. It is also possible that the diesel engine has been used for a long time, and the vent hole of the fuel tank cover is blocked by dust and other dirt. After the hole is blocked, the fuel tank is difficult to communicate with the atmosphere. As the oil level drops, negative pressure will be generated on the upper part of the fuel tank, which affects the supply of diesel, and even causes the interruption of fuel supply.
(3) The oil pipe or diesel filter is blocked. If the oil pipe is bumped and deviated or the filter screen of the pipe connector is not cleaned for a long time, the oil circuit will also be blocked; Once the oil pipe is deformed or the diesel filter element is blocked by impurities, the oil pipe shall be replaced or the filter element shall be cleaned in a timely manner. Otherwise, the oil pipe and filter element are blocked, which will cause difficulty in starting the diesel engine.
(4) The plunger pair or outlet valve pair of the fuel injection pump is seriously worn, and the sealing performance becomes poor. It will lead to the reduction of the pump oil pressure of the fuel injection pump, the untimely fuel injection, the insufficient fuel combustion, and finally the difficulty in starting the diesel engine.
(5) The injector injects fuel too early or too late. The fuel injection timing of the injector is mainly determined by the fuel supply advance angle of the diesel engine. If the fuel supply advance angle is too large and the fuel injection time is too early, the compression pressure in the cylinder has not reached the required value and the temperature in the cylinder is relatively low, which will directly affect the fuel combustion performance, resulting in early combustion of the diesel engine and incomplete fuel combustion. If the fuel injection advance angle of the diesel engine is too small and the injection time is too late, the best time for fuel injection into the cylinder has passed, which will increase the afterburning of the diesel engine and cause a large amount of fuel to be discharged from the cylinder before fully burning. In short, premature or too late injection time will cause insufficient power of the diesel engine and affect the normal starting of the diesel engine.
(6) Poor fuel atomization or no fuel injection. The carbon deposit on the fuel injection nozzle will make the fuel injection not smooth and the fuel atomization quality will decline, which will make it difficult to fully burn the fuel after it enters the combustion chamber, causing difficulties in starting the engine, unstable idle speed, increased fuel consumption and worsening exhaust emissions.
(7) The temperature is too low and the viscosity of diesel oil is too high. Due to the large compression ratio of the diesel engine, coupled with the high viscosity of the engine oil in winter and the slow speed of the engine oil on the lubricating system, the power of the starter is insufficient, the starting speed is slow, the compressed air in the combustion chamber cannot reach the diesel combustion temperature, and the diesel oil becomes viscous and has poor fluidity due to cold weather, resulting in poor oil injection quality and difficult starting of the diesel engine.