Problems Easily Neglected in Diesel Engine Maintenance

1. Only replace the plunger and nozzle, ignoring the technical status of the delivery valve. After the fuel delivery valve is worn, the remaining pressure of the high-pressure fuel pipe will be too high, causing the fuel injection nozzle to cut off the fuel and dripping oil, causing the diesel engine exhaust to smoke, knock the cylinder, and run unstable. The method is to check the oil outlet valve and use a pressure gauge with a range of 0-600 kg/cm² to detect. When the gauge needle drops from 200 kg to 180 kg/cm², the pressure holding time should be longer than 15 seconds, otherwise the oil outlet valve should be replaced; or The high-pressure oil pipe port is upward, and the diesel oil is pumped out, so that the oil level is flush with the pipe port, put the throttle back to the stop position, violently reverse the traveling wheel half a turn, the diesel oil at the high-pressure oil pipe port is qualified if it is not sucked back, otherwise the oil outlet valve should be replaced .

2. Only adjust the valve clearance and ignore the valve timing. Most people just adjust the valve clearance according to the value specified in the manual, but neglect to check whether the valve timing is correct. Especially for aging machines, the geometric shape changes after the cam wears, causing the valve to open late and close early, which will result in insufficient intake, poor exhaust, increased fuel consumption, and decreased power. Therefore, when adjusting the valve clearance of old diesel engines, the value of the valve clearance should be appropriately reduced according to the mechanism to make up for the error of the valve valve phase. For example, in the S195 diesel engine, each time the valve clearance decreases by 0.1 mm, the valve valve phase changes by 3 degrees. However, the valve clearance should not be less than 0.2 mm, otherwise the valve will not close tightly due to the influence of expansion. If the valve clearance is already 0.2 mm, and the valve phase error is still more than 5 degrees, and the working condition of the diesel engine is significantly deteriorated, the camshaft should be replaced.

Third, only look at the amount of oil in the sump and ignore the quality of the oil. Many people just replenish the engine oil, never check the quality of the oil, and never change it. As everyone knows, the waste engine oil that should be replaced contains a lot of oxidizing substances and metal shavings, which reduces the lubrication performance, aggravates the wear of the parts, and shortens its service life. Therefore, the quality of the engine oil in the engine should be checked at any time. The general method is to twist and grind the oil by hand. If you feel that there is mechanical impurities or the viscosity is not enough, you should replace it in time. Another inspection method is to drop the used engine oil on white paper, such as small black spots and light color.

Four, only know to maintain the air filter, ignore the air short circuit. There are many reasons for the air short circuit. For example, the air inlet pipe of the air filter fixed on the tricycle frame is not welded properly, the air inlet pipe joint is not equipped with a sealing gasket, the air inlet pipe is inserted into the hose loosely without a clamp, and the air inlet hose is not broken. It is found that the lack of apron in the air filter, etc., will cause air short circuit, causing unfiltered air to enter the cylinder, and aggravate the wear of the cylinder, piston, piston ring, valve and other parts.

5. Only clean the oil filter screen and neglect the cleaning of the purifying oil chamber. Most diesel engine connecting rod journals are hollow with oil plugs at both ends, which are called clean chambers. Under the action of centrifugal force, the oil for lubricating the connecting rod bearing bush adheres to the cavity wall, thereby improving the quality of lubrication. Generally, the oil plug must be removed every 500 hours of operation of the diesel engine.