As for the cause of diesel engine oil pressure low alarm, the following is a detailed analysis:

I. Oil pressure drop due to insufficient oil output from engine oil pump:

Oil pump gear pump and rotor pump two kinds. Some gear pump (such as 4125 diesel engine oil pump), the pump cover and pump body joint surface roughness is very low, the original design does not add gasket, if the maintenance of their own paper pad, will increase the gear end clearance, but will reduce the pump oil output. However, there is a gasket at the joint surface between the pump and the cylinder block. If the gasket is missed, the pressure oil from the oil pump will leak outwards, thus causing the oil pressure to drop. Some rotor pump, the outer rotor side has chamfered, the other side without chamfered, if installed backwards, the amount of oil can be reduced by 40% to 60%. In addition, gear or rotor radial and end clearance due to wear and too large, will lead to the pump oil output and oil pressure decline in the adverse consequences.

Countermeasures: After repair, the oil pump should go on the test bench to adjust the opening pressure of the pressure limiting valve to keep it between 0.5-0.7mpa. If the pressure is too high, the accelerator oil pump will wear; If the pressure is too low, it will cause the pressure of the main oil channel to drop. Install the oil pump should be filled with oil first, in order to avoid the pump air and suction oil. The connection between the oil pump and the oil absorption pan must be sealed. If there is air leakage, the oil output of the oil pump will also be reduced. (Magneto triode)

Ii. Oil pressure drop caused by clogged oil filter:

1. When the oil filter is blocked and the oil cannot pass through smoothly, the safety valve on the base of the filter will be jacked open, so that the oil can enter the main oil channel directly without filtering. However, if the opening pressure of the relief valve is too high to open in time, it will increase the leakage in the oil pump and reduce the amount of oil supplied to the main oil channel, and the oil pressure will decrease accordingly.

Countermeasures: The oil filter should be maintained on time, and the opening pressure of the safety valve should be adjusted to 0.35-0.45mpa.

2, in addition, if the relief valve spring aging, valve seat and ball sealing is not strict, oil will also be a large number of leakage, and cause oil sump oil bubble, at this time the oil ruler can see covered with foam oil. If the return oil valve spring is softened or adjusted improperly, the valve seat and steel ball mating surface are worn or stuck by dirt and do not close strictly, the return oil volume will rise substantially, and the oil pressure of the main oil channel will also decrease accordingly.

Countermeasures: The oil return valve should be repaired and the opening pressure adjusted to 0.28-0.32mpa.

3. The oil return valve is damaged and causes the oil pressure to drop. In order to maintain the normal oil pressure of the main oil channel, the oil return valve is set here. In addition, if the return oil valve opening pressure is too low, the machine will cause the return oil valve to open and close frequently, thus causing the oil pressure gauge pointer to swing back and forth, the main oil channel is also prone to burn tile accident due to insufficient oil supply.

Countermeasures: Replace the return oil valve.

4, oil radiator oil leakage caused oil pressure drop. Leakage of oil not only makes the machine dirty, but also causes the oil pressure to drop.

Countermeasures: should be removed from the radiator welding repair, after passing the pressure inspection can be installed. Some machines, such as the American E200 excavator and the domestic T-120 bulldozer, the oil radiator is directly placed in the body cooling system, if the radiator oil leakage, machine operation due to the oil pressure higher than the cooling water pressure, the oil in the radiator will flow into the water; When the machine is turned off, the cooling water will permeate into the radiator, making the oil emulsified and deteriorated quickly. Remove the radiator for welding and replace the invalid oil before resuming work. In addition, if the oil radiator and pipeline is blocked by dirt, it will increase resistance and reduce oil flow, pressure drop. Should dredge in time, restore its normal circulation capacity.