Main causes of low oil pressure:

1. Insufficient oil

If the amount of oil is insufficient, the amount of oil pumped by the oil pump will be reduced or the oil will not be pumped due to the air entering, which will reduce the oil pressure. The crankshaft and bearing, cylinder liner and piston will be worn more severely due to poor lubrication.

2. Oil pump does not rotate

If the flat key between the drive gear and drive shaft of the oil pump is damaged or falls off; If the oil pump sucks foreign matters due to the damage of the filter collector and the gear is stuck, the oil pump will stop running and the oil pressure will drop to zero.

3. Wear of oil pump

When the clearance between the pump shaft and bushing of the oil pump, the clearance between the gear end face and the pump cover, the clearance between the gear side or the radial clearance is too large due to wear, the pump oil volume will be reduced and the oil pressure will be reduced.

4. Engine temperature too high

If the engine cooling system has too much scale, poor heat dissipation, long time overload operation, or the fuel supply time of the fuel injection pump is too late, the engine will overheat, accelerate the aging, deterioration, thinning of the oil, leak from each fitting clearance, and reduce the pressure.

5. The fit clearance between main bearing and connecting rod bearing increases

After the engine has been used for a long time, the fit clearance between the main crankshaft and the connecting rod bearing gradually increases, the leakage increases, and the oil pressure decreases.

6. The bypass valve is damaged

In order to maintain the normal oil pressure of the main oil passage, a bypass valve is set. If the pressure regulating spring is softened or improperly adjusted, the fitting surface between the valve seat and the steel ball is worn or jammed, and the valve is not closed tightly, the oil return volume will increase, and the pressure of the main oil passage will decrease.

7. Oil radiator leaks

The leakage will pollute the engine surface and reduce the pressure; The internal leakage makes the oil enter the water tank, the cooling effect of the cooling system becomes worse, the engine overheats, the oil becomes thinner, and the pressure drops.

8. Pressure sensor failure or oil passage blockage

If the pressure sensor fails or the oil passage from the main oil passage to the pressure sensor is blocked and the oil flow is blocked, the oil pressure will drop.

9. The set pressure of pressure limiting valve is too low

In the lubricating system, the oil pumped by the oil pump must be kept at a proper pressure before reaching the lubricating parts of the engine. If the set pressure of the pressure limiting valve is too low, the pressure regulating spring becomes soft or the sealing surface leaks, the set pressure will be too low.

10. Improper oil grade

If the selected oil is unsuitable or inferior, the engine will leak more and the pressure will decrease due to the low viscosity.

11. Plugged oil filter

When the oil filter is blocked and cannot flow, the bypass valve on its base is opened, and the oil directly enters the main oil passage without filtering. If the opening pressure of the bypass valve is set too high, when the oil filter is blocked, it cannot be opened in time, the pressure of the oil pump will rise, the internal leakage will increase, and the oil supply to the main oil passage will decrease, and the oil pressure will decrease.

12. Clogged filter collector

Under normal conditions, the oil pressure at large throttle should be higher than that at small throttle, but sometimes abnormal conditions may occur. If the oil is too dirty and sticky, it is easy to block the filter collector. When the engine runs at low speed with small throttle, the oil pressure is normal because the oil suction of the oil pump is not large and the main oil passage can still build up a certain pressure; However, when the accelerator is increased and the engine runs at a high speed, the oil suction of the oil pump will obviously decrease due to the excessive resistance of the filter collector, so the indication of the oil pressure gauge will decrease due to insufficient oil supply in the main oil gallery.