Causes and Solutions of Abnormal Oil Pressure of Diesel Engine

1. The oil pressure is too high

Too high oil pressure means that the oil pressure gauge exceeds the specified value.

1.1 Oil pressure display device is not normal

The oil pressure sensor or oil pressure gauge is abnormal, the pressure value is inaccurate, the display value is too high, and the oil pressure is mistakenly considered to be too high. Adopt the exchange method (i.e. replace the old sensor and pressure gauge with the good oil pressure sensor and pressure gauge). Check the new oil pressure sensor and oil pressure gauge. If the display is normal, it indicates the old pressure display device is faulty and should be replaced.

1.2 Excessive oil viscosity

The oil viscosity is too large, the fluidity becomes poor, the flow resistance increases, and the oil pressure increases. If in summer, oil is selected which use in winter, the oil pressure will increase due to excessive viscosity. In winter, due to the low temperature, the oil viscosity increases, and the pressure will be too high in a short time when starting the engine. However, after stable operation, it gradually falls back to the specified value with the rise of temperature. During maintenance, the specified brand of engine oil shall be selected according to the requirements of technical data; Warm up measures shall be taken when starting the engine in winter.

1.3 The clearance of pressure lubrication part is too small or the secondary oil filter is blocked

The matching clearance of pressure lubrication parts, such as cam bearing, connecting rod bearing, main crankshaft and rocker arm bearing, is too small, and the filter element of the secondary filter is blocked, which will increase the flow resistance and pressure of the oil circuit of the lubrication system.

The engine oil pressure after overhaul is too high, which is often due to the small fit clearance of the bearing (bearing bush) at the pressure lubrication part. The engine oil pressure that has been used for a long time is too high, which is caused by the blockage of the fine oil filter. It should be cleaned or replaced.

1.4 Improper adjustment of pressure limiting valve

The oil pressure depends on the spring force of the pressure limiting valve. If the adjusted spring force is too large, the pressure in the lubrication system will increase. Readjust the spring force of the pressure limiting valve to make the oil pressure fall back to the specified value.

2. The oil pressure is too low

Low oil pressure means that the display of the oil pressure gauge is lower than the specified value.

2.1 The oil pump is worn or the sealing gasket is damaged

The internal leakage of the internal gear of the oil pump increases due to wear, which makes the oil pressure too low; If the gasket at the joint of the filter collector and the oil pump is damaged, the oil suction of the oil pump is insufficient and the oil pressure is reduced. At this time, check and repair the oil pump and replace the gasket.

2.2 Reduction of oil volume of suction pump

If the amount of oil in the oil pan is reduced or the oil pump strainer is blocked, the oil suction of the oil pump will be reduced, resulting in the reduction of oil pressure. At this time, check the oil quantity, add oil and clean the oil pump filter collector.

2.3 Large oil leakage

There is leakage in the pipeline of the lubrication system. Due to wear and excessive fit clearance at the crankshaft or camshaft, the leakage of the lubrication system will increase and the oil pressure will decrease. At this time, check whether the lubrication pipeline is broken, and check and adjust the fit clearance of bearings at crankshaft and camshaft as required.

2.4 Blocked oil filter or cooler

With the extension of service time of oil filter and cooler, mechanical impurities and other dirt increase, which will reduce the cross section of oil flow, or even block the filter and cooler, resulting in the reduction of oil pressure at the lubricating part. At this time, check and clean the oil filter and cooler.

2.6 Improper adjustment of pressure limiting valve

If the spring force of the pressure limiting valve is too small or the spring force is broken due to fatigue, the oil pressure will be too low; If the pressure limiting valve (affected by mechanical impurities) is not closed tightly, the oil pressure will also drop. At this time, clean the pressure limiting valve and adjust or replace the spring.

3. No oil pressure

No pressure means that the pressure gauge displays 0.

3.1 The oil pressure gauge is damaged or the oil pipeline is broken

Loosen the pipe joint of the oil pressure gauge. If pressure oil flows out, the oil pressure gauge is damaged. Replace the pressure gauge. A large amount of oil leakage due to the rupture of the oil pipeline will also cause no oil pressure. The oil pipeline should be overhauled.

3.3 Oil pump damage

The oil pump has no oil pressure due to severe wear. Repair the oil pump.

3.4 The oil filter paper pad is installed reversely

When overhauling the engine, if you do not pay attention, it is easy to install the paper pad at the connection between the oil filter and the cylinder block reversely, and the oil inlet hole is connected with the oil return hole. The oil cannot enter the main oil passage, resulting in no oil pressure. Reinstall the paper pad of the oil filter.