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How to check the oil pressure of diesel generator set is too low

May 17, 2022
The oil pressure of the diesel generator set is too low, which is a common fault in the use and maintenance of the diesel generator set. When the diesel generator set is at a hot idle speed, the oil pressure is lower than 0.1MPa, and it is lower than 0.2MPa at medium and high speed. Pressure too low. So how to check if the oil pressure of diesel generator set is too low?
1. Appearance inspection
1. Check oil quality and quantity
For diesel engines with too low oil pressure, generally check whether the oil quantity meets the requirements. If the amount of oil is too small, the fault is obvious. If the amount of oil meets the requirements or is too much, you should carefully observe whether the oil has diesel oil or moisture. If the oil is mixed with diesel, the oil will become thinner and the viscosity will drop, resulting in too low oil pressure.
2. Observe the oil pressure sensor and oil pressure gauge
Turn on the power (do not start the diesel engine at this time), observe whether the pointer of the oil pressure gauge moves and returns to the "0" position accurately. If the pointer of the oil pressure gauge does not move or cannot return to "0", the oil pressure gauge is inaccurate, or the oil pressure sensor fails, or the circuit is faulty.
A self-made direct-pressure oil pressure gauge (remanufactured with a 0.1-1.0 MPa air pressure gauge) can be connected in series on the main oil passage to start the diesel engine. If the oil pressure on the direct-pressure gauge is normal, the fault is still related. If the pressure on the direct pressure gauge is too low and there is no abnormal noise in the diesel engine, you can first debug the oil high pressure valve of the main oil passage of the diesel engine and the pressure regulating valve on the oil coarse filter to observe the debugging effect.
2. In-machine inspection
1. Oil sump inspection
When the above appearance inspection and debugging are invalid, drain the oil, disassemble the oil pan, and check: whether there are babbitt shedding in the oil sump, especially block shedding and other abnormal conditions; oil filter Whether the filter screen of the oil pump is blocked; whether the welding parts of the oil suction pipe and the oil outlet pipe of the oil are blocked, whether the sealing gaskets at each end are firm and effective; whether the firm sealing of the oil pump cover is effective; whether the oil pump driving gear and the oil pump shaft bushing are abnormally worn .
2. Check for pressure and leaks
After the above observation and inspection are considered to meet the requirements, the fault that causes the oil pressure to be too low has not been found. Generally, do not rush to disassemble or replace the relevant parts. According to experience, compressed air can be connected to the main oil passage (reform a joint corresponding to the thread size of the main oil passage and a high-pressure hose connected with the air source), and the air pressure should be 0.4~0.5Mpa. Directly observe or touch the degree of compressed air leakage at the clearance of the main bearing connecting rod bearing, and observe and analyze the following common abnormal situations of compressed air leakage:
       (1) In the same type of bearing, if the amount of compressed air leaked by a bearing is relatively large and rapid, then generally the bearing has the babbitt alloy falling off or the bearing wear is too large;
       (2) If there is obvious air leakage at the oil pump shaft and bushing, it can be judged that the internal wear of the oil pump is too large;
       (3) There is obvious air leakage in the oil return hole on the inner side of the cylinder block where the rotor filter is installed, indicating that the rotor shaft is worn too much;
       (4) There is air leakage inside the cylinder block where the oil pre-filter is installed, generally because the gasket of the oil pre-filter assembly is damaged or installed backwards;
       (5) There is obvious air leakage at the timing gear chamber, and it should generally be judged that the idle gear and the shaft are not properly matched;
       (6) If there is compressed air leakage in the main oil passage or other oil passages inside the cylinder block, it can be judged that there are casting sand holes or cracks in the oil passage, especially for the new cylinder block, this point should be checked;
       (7) If necessary, remove the cylinder head cover at the same time to check the leakage of the valve rocker arm mechanism. If there is uneven leakage, it means that the related parts are too loose (the crankshaft should be turned at this time).