• General troubleshooting methods

1. Why is it more difficult to start the engine in winter?

The starting of the engine is not only determined by its own technical conditions, but also affected by the outside temperature. It is more difficult to start at low temperature in winter, mainly due to the following reasons:

⑴ In winter, the climate is cold, the ambient temperature is low, the viscosity of the oil increases, and the frictional resistance of various moving parts increases, which reduces the starting speed and makes it difficult to start.

(2) The capacity of the battery decreases as the temperature drops, which further reduces the starting speed.

⑶Due to the reduction of the starting speed, the leakage of compressed air increases, and the heat dissipation of the cylinder wall increases, resulting in a great decrease in the temperature and pressure of the air at the end of compression, which increases the delay period of diesel ignition, and even can not burn in severe cases.

(4) The viscosity of diesel oil at low temperature increases, which reduces the injection speed. In addition, the swirl velocity, temperature and pressure of the air at the end of compression are relatively low, so that the atomization quality of the diesel injected into the cylinder is poor, and it is difficult to quickly form a good quality with the air. The flammable gas will ignite and burn in time, or even fail to catch fire, resulting in difficulty in starting.

2. Conditions for good engine starting performance

(1) There must be enough starting speed. The starting speed is high, the gas leakage in the cylinder is small, the heat transfer time of the compressed air to the cylinder wall is short, and the heat loss is small, so that the gas temperature and pressure at the end of the compression can be improved. Generally, the speed is required to be above 100 r/min.

(2) The tightness of the cylinder is better. This can further reduce the amount of air leakage, ensure that the gas has sufficient combustion temperature and pressure at the end of compression, and the compression pressure of the cylinder shall not be lower than 80% of the standard value.

(3) It is required that the matching clearance between the engine and the running parts is appropriate and well lubricated.

⑷ The battery must have sufficient starting capacity, and the technical condition of the starting circuit is normal.

⑸ The amount of starting oil meets the requirements, the injection quality is good, and the injection advance angle must meet the requirements.

⑹ Use fuel that meets the requirements.

3. Diagnosis and repair of mechanical faults that the crankshaft cannot rotate when the engine is started

When the engine is started, under the condition that the starting system is in good condition, if the transmission is placed in the neutral position and the start switch is pressed, the starter makes a noise and the crankshaft cannot rotate, which is a mechanical failure. The causes, diagnosis and repair methods of the engine crankshaft not rotating are as follows.

⑴ Reason

① The starter and the flywheel teeth are poorly meshed. The ring gear and the starter gear will collide when starting the engine, causing damage to the teeth or single-sided wear of the teeth. If three or more teeth are continuously damaged or severely worn, it will be difficult for the starter gear to mesh with the ring gear teeth.

②Stick the cylinder. When the engine temperature is too high, the engine stops and stops, and the heat is difficult to dissipate. The piston ring and the cylinder are adhered at high temperature, and it cannot be started after cooling.

③The crankshaft is locked. Due to the failure of the lubrication system or the lack of oil, the dry friction of the sliding bearing causes the crankshaft to be locked and unable to start.

④The plunger of the fuel injection pump is stuck.

(2) Diagnosis and repair methods

①If the flywheel has more than three consecutive teeth damaged, and it is exactly opposite to the starter teeth, the two gears will not be able to mesh. In this state, just use a spudger to pry the flywheel to an angle, and then press the start button to start smoothly. For damaged flywheel teeth, welding can generally be used to repair.

②When the ring gear is loose, it can be confirmed from the installation port of the flywheel housing starter. If the ring gear is loose, it must be replaced with a new one. When installing, the ring gear should be heated in the heating box first, and then pressed on the flywheel while it is still hot, and then it can be fastened to the flywheel after cooling.

③When the teeth of the ring gear are severely worn on one side, the ring gear can be pressed down, and the front and rear faces can be turned over before being installed on the flywheel for use.

④ After checking that the gear meshing is normal, and the flywheel does not rotate when starting, it should be regarded as an internal fault of the engine, such as crankshaft lock, piston sticking cylinder, clutch stuck, etc., which should be further observed. You can first check whether the clutch is damaged and stuck, and then check whether the plunger of the fuel injection pump is stuck and whether there are foreign objects inside the engine.