Common Fault Diagnosis and Removal of Lubrication System
The common failures of the lubrication system are: oil deterioration; abnormal oil consumption; oil pressure is too high; oil pressure is too low.
Oil deterioration
1) Phenomenon
Sampling and inspection of the phenomenon oil turns black, rubbing with fingers, loses stickiness and has a sense of impurities; oil containing water is milky and foamy.
2) The reason
The reason is that the oil has been used for too long; Oil leakage from piston ring; poor ventilation in crankcase oil mixed with fuel in exhaust gas; engine block cracks, cooling water leakage into the oil pan; oil pump wear, decreased oil supply capacity; oil filter too dirty, blocked or The sealing is not good, so that the lubricating oil circuit is short-circuited; the lubricating oil circuit is blocked.
3) Diagnosis and exclusion
Take a few drops of oil on the neutral filter paper with an oil dipstick, and check the oil stains after it has diffused. If the black impurities in the center are darker and the particles are thicker, it means that the oil contains many impurities and has deteriorated; If the oil loses its stickiness, it means that the oil is mixed with fuel. It is necessary to check whether the ventilation of the crankcase is good and whether the air leakage of the piston is too large. If the oil contains moisture, check the cylinder wall for cracks and leakage; if necessary, check whether the filter fails and whether the oil passage .
Abnormal oil consumption
1 Phenomenon
The oil consumption rate exceeds 0.1~0.5L/4h, the exhaust pipe emits blue smoke, and the oil filling port pulsates and emits smoke.
2) The reason
The reason is that the gap between the piston and the cylinder wall is too large; the elasticity of the piston ring is reduced, locked or aligned, the piston ring is worn too much, so that the end clearance, side clearance and backlash are too large; the twisted piston ring is installed incorrectly; the intake valve guide is worn too much ; Poor ventilation of the crankcase; Oil leakage at the rear end of the engine crankshaft; Oil leakage at the engine timing gear cover; Oil leakage from the oil pan or valve cover (cover). The circle grows out of the mother:
3) Diagnosis and elimination
A First check whether there are oil leaks on the outside of the engine: then run the engine at high speed to see if blue smoke is coming from the exhaust pipe, and sometimes you can see pulsating from the oil filler port The blue smoke indicates that the oil enters the combustion chamber of the cylinder, and the piston connecting rod group should be checked and analyzed. If only blue smoke is emitted from the exhaust pipe, and there is no pulsating blue smoke from the oil filler, it means that the oil in the valve chamber is sucked into the combustion chamber along the excessively worn valve guide.
Oil pressure too high
1) Phenomenon
When the ignition switch is turned on, the oil pressure gauge indicates 196kPa. After starting, it increases to more than 490kPa. When the engine is running, the oil pressure gauge indicates a sudden increase. Sometimes the oil pressure gauge increases and then suddenly drops.
2) The reason
the reason is that the oil viscosity is too large; the pressure limiting valve is not adjusted properly; the clearance of the newly assembled engine crankshaft bearing or connecting rod bearing is too small; the main oil passage of the cylinder block is blocked; the oil filter element is blocked and the bypass valve is difficult to open; the oil pressure The meter is inaccurate or the sensor fails; the oil pressure increases, the oil circuit ruptures somewhere, a large amount of oil is drained, and the pressure drops suddenly.
3) Diagnose and rule out
The engine oil pressure is too high, immediately turn off the engine and stop for inspection. First check whether the oil viscosity is too large, and then use the new oil pressure gauge and sensor to compare the old one to check whether the oil pressure gauge and sensor fail. If the above inspections are good, disassemble and check whether the pressure limiting spring is too hard, and then check whether the clearance between the crankshaft bearing and the connecting rod bearing is too small, whether the oil filter element is blocked, whether the bypass valve spring is too hard, and whether the main oil passage of the cylinder block is too small. Is it blocked.
Oil pressure too low
1) Phenomenon
After the engine is started, the oil pressure decreases quickly; during the engine operation, the oil pressure is always too low; the oil in the oil pan is diluted, the oil level increases, the oil viscosity decreases, and there are water droplets
2) Reasons
Reason for insufficient oil volume; too small oil viscosity; too soft or improper adjustment of the pressure limiting valve spring; broken or too soft spring of the oil filter bypass valve; poor sealing of the sealing surfaces of the lubrication system, valves and pipe joints or The lubricating oil passage is broken and the oil is filled: the oil pump is not working properly; the oil filter is blocked; the crankshaft main bearing, connecting rod bearing or camshaft bearing space is too large; the oil gauge or sensor fails; the cylinder gasket is damaged or the bushing is cracked, Cooling water leaked into the oil pan.
3) Diagnosis and troubleshooting
Check whether the oil quantity is insufficient, the viscosity becomes smaller, and whether there is leakage. Remove the sensor and run it for a short time to see if the oil is strong. If it is weak, check whether the filter element, bypass valve, pressure limiting valve, oil inlet pipe, filter, and oil pump are working properly. If the oil is strong, replace the new sensor, check whether the meter and sensor are invalid, and if necessary, check whether the clearance between the crankshaft bearing and the connecting rod bearing is too large. If the pressure is found to be too low during the operation, you can directly remove the main oil passage screw plug or sensor to observe whether the fuel injection is strong. Weakness should be checked immediately.
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