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How to Deal With Oil Pressure of Diesel Generator Set

Oct. 26, 2018

Common faults in diesel generator set lubrication systems include: low oil pressure, high oil pressure, excessive oil consumption, increased oil level and oil pump noise. Let's take a look at the situation where the oil pressure is too high or too low.

How to Deal With Oil Pressure of Diesel Generator Set.jpg


I The oil pressure is too high, the oil pressure gauge indicates that the specified value is exceeded, and the engine power is reduced.



1. The oil viscosity is too large.

2. The pressure limiting valve is improperly adjusted or the spring is too hard.

3. The oil filter is clogged and the bypass valve top is not open.

4. The bearing clearance is too small.

5. The oil after the oil pressure gauge The pipe is blocked.


Method of exclusion


1. Check the viscosity of the oil, take the oil gauge off the crankcase, drop a few drops of oil on the finger, and use your fingers to feel the viscosity of the oil is too large. When the viscosity is too large, the oil may be incorrectly graded and the oil of the appropriate grade should be replaced.


2. Check the pressure limiting spring and bypass valve spring to see if the pressure is too tight or the spring is too strong to open. Adjust, clean or replace in time.


3. Check the bearing clearance and the oil pipelines in the cylinder. For the newly repaired engine, check whether the bearings are over-tightened and whether the oil passage leading to the crankshaft bearing is blocked. If it is blocked, it will easily lead to burnt tile accidents.


II The oil pressure is too low, which means that the oil meter has no indication/indication below the specified value, or the oil pressure gauge is normal when the machine is started, and then drops, or even zero.




1. The oil quantity is insufficient.

2. The oil viscosity is too small (low grade, high temperature, mixed with fuel or water)

3. The pressure limiting valve is not adjusted properly, the  spring becomes soft

4. The oil pressure gauge and the sensitive plug are invalid.

5. The oil filter screen and oil pipeline are blocked.

6. There is oil leakage in the lubricating oil channel.

7. Oil pump oil capacity is poor.

8. The bearing clearance is too large.


Method of exclusion


When the oil pressure is too low, the diesel engine is stopped first, and after waiting for 5 minutes, the quantity and quality of the engine oil are checked out with the oil gauge. Insufficient oil should be added with the same number or engine oil in the oil basin. If the oil viscosity is small, the oil level is elevated, and the oil smells of raw oil, the oil is mixed with oil. If the oil color is milky, the oil is infiltrated into the oil. If oil is leaking, the oil should be changed according to the regulation.


Because of the seasonal change, the engine oil pressure of the diesel engine will be reduced if the engine oil number is not changed in time, or if the engine oil brand number is not consistent with the oil brand number in the oil basin.


1. When the engine is overheated, it should be considered that the decrease of oil pressure may be caused by excessive oil temperature and oil thinning. In this case, the engine oil pressure is normal when the engine oil is cooled and the generator set is started.


2. Adjust the pressure limiting valve to normal pressure or check that the spring elasticity of the pressure limiting valve is weakened.


3. Check the oil pressure gauge, remove the original oil pressure gauge and install a new one for comparison. Check pressure plug, remove pressure plug from cylinder block, plug hole with rag. Briefly start the machine, if the oil from the oil channel is sufficient, and no bubbles, indicating that the plug failed. If the oil is out of the channel and there are bubbles, the low oil pressure may be caused by the poor oil pipeline.


4. Check the oil filter, the machine oil pump and the oil channels, remove the oil filter, rotate the crankshaft, observe the oil outlet of the machine oil pump. If the oil is not much or does not produce oil, it may be that the engine oil pump does not pump the oil or the filter is blocked. The repairman oil pump or cleaning filter should be checked. Remove the oil pan and check if the oil filter is clogged, or if the engine oil pump is worn out or even underladed. If there are bubbles in the lubricating oil ejected from the oil channel, the connection of the oil pump and the oil pump is broken or loosened.


5. Check the bearing clearance, if the crankshaft, connecting rod, camshaft and other parts of the bearing clearance is too large, at the beginning of the machine, because of the viscosity of oil, oil is not easy to lose, the pressure can reach the normal value. However, when the machine is heated, the viscosity of the oil becomes thinner and the oil is squeezed from both sides of the bush, thus reducing the oil pressure.


Causes and treatment of too high or too low injection pressure of diesel generator injector


I The main reasons for the excessive injection pressure of the fuel injector in the diesel generator set.


1. Pressure adjustment of pressure regulating spring.

2. Needle valve stuck in valve body

3. Nozzle plugging


II Main causes of low fuel injection pressure in diesel generator injector


1. Adjustable spring pressure adjustment too small or broken

2. Pressure regulating screw loosening

3. Needle valve guide part and needle valve body clearance is too big or needle valve cone surface seal is not strict.

4. The sealing of the contact surface between the nozzle and the injector is not strict.


III processing method


Appropriate adjustments and repairs should be made at this time. The fuel injection pressure of the injector is clearly stipulated in the specification of each machine, so it should not be adjusted too high or too low at random, otherwise, it will cause the in-homogeneous operation of each cylinder of the diesel engine, the decrease of power and even the early wear and tear of the combustion chamber and piston and other parts. Generally speaking, if the fuel injection pressure is adjusted too low, the atomization of the fuel injection will be greatly deteriorated, the diesel fuel consumption of diesel generator set will increase, and it is difficult to start. Even after starting the exhaust pipe will always smoke, injector needle valve is easy to deposit carbon. Too high fuel injection pressure adjustment is also not good. At this time, it is easy to cause the machine to produce a knock sound while working, and make the power drop. At the same time, it is easy to wear the plunger coupling and injector of the fuel injection pump, and sometimes crack the high pressure tubing.


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