Checking the cylinder seal state by compressed air method Feng Guoshun, the road transport management office of Huainan City, China. The cylinder seal state of Geyong engine of China Chemical Engineering Third Construction Company Overhaul Factory directly affects its power, economy and work stability. Careful attention should be paid to repair and use. Under normal circumstances, when there is a problem with the cylinder seal, it must affect the realization of the ideal pressure at the end of the compression stroke, which is usually called leakage compression. The parts that generate leakage compression mainly include: the seal between the piston and the cylinder wall, the seal between the exhaust valve and the valve seat, the seal between the cylinder head and the cylinder head gasket, and the spark plug (the injector of the diesel engine) and its matching hole. The seal between the two. When a similar problem occurs, the cylinder first fails to work and the power is reduced. The usual judgment method is the fire test, stop the cylinder work, observe the change of the engine idle working condition, and then observe the water tank (water-cooled engine) and the temperature rise of the body, the water tank flipping condition and the presence or absence of air bubbles, can also be used The cylinder pressure gauge tests the pressure of the cylinder at the end of compression, and then makes a comprehensive judgment and analysis to find out the specific reasons and troubleshoot. This will not be elaborated here. The following is a specific method for static inspection of engine cylinder leakage compression parts using compressed air for repair by peers or vehicle users.
1 The main facilities involved (1) First use the compressed air source: small air compressor or the car's own compressed air package.
(2) Pre-processing a set of through-hole joints with the engine spark plug screw 1 pipe joint 2 sealing ring 3 pipe joint nut 4 pipe joint pattern. (Fig. 1) (3) Prepare a hose with the length from the spark plug hole of the engine cylinder to the compressed air source. The inner diameter should be tightly clamped on the nozzle.
2 Check the specific method of the cylinder leakage compression part (1) When the valve clearance meets the normal requirements, place the transmission in the neutral position, unscrew the spark plug of each cylinder, start the motor at the above speed, and drive the engine to run. The cylinder pressure gauge is used to assist in measuring the final compression pressure of the cylinder to be inspected. If the cylinder pressure is significantly lower than the standard value of the model, the specific part of the leakage compression can be further checked by inputting compressed air into the cylinder.
(2) Shake the engine crankshaft or toggle the flywheel ring gear so that the piston of the cylinder to be inspected reaches the top dead center position at the end of the compression stroke. At this time, the intake and exhaust valves of the cylinder are at the closing time.
(3) Screw the union with the hose attached to the spark plug hole of the cylinder to be tested, and input compressed air equivalent to the standard compression pressure of the model to the cylinder. (The connection line is as shown in (4) Observing the pressure drop of the pressure gauge. When there is no leakage between the pipeline and the airbag, and the gauge pressure reading drops, the cylinder is leak-compressed. At this time, because the engine is not working, around The environment is free of noise, and the degree of leakage compression is not only apparent from the table, but also through the eye, the ear (or by the speaker amplifier) ​​to determine the specific part of the leak.
1 When there is air bubble in the water tank or there is air leakage in the adjacent cylinder, it indicates leakage between the cylinder head gasket and the cylinder head.
2 If there is a leaking sound in the crankcase, the sealing of the piston ring and the cylinder wall is poor. (Piston ring is opposite, the elastic force is too weak, the clearance is too large, or the cylinder wall is seriously worn, etc.) 3 If there is air leakage in the intake pipe, the intake valve is poorly sealed, and the closing is not strict (the valve clearance is too small or even no gap, resulting in The valve cannot be closed, etc., or the valve seal band is burnt, etc.
4 If there is air leakage in the exhaust pipe, the reason for the drop is similar to that of 3.
3 Using compressed air to check the leakage of cylinders should pay attention to the matters in order to make this leak detection work cheaper, the results are more accurate, should pay attention to the following points: (1) use the starter to drive the engine to run, detect the end of each cylinder compression Before the pressure, the valve clearance should be checked according to the requirements of different models. Measuring the engine speed when the cylinder pressure is compressed (2) When performing the leak compression test, make sure that the piston of the cylinder under test is at the end of the compression stroke (ie, the piston is to the top dead center and the intake and exhaust valves are closed). When the flywheel is moved (or another method of manually operating the crankshaft), the top dead center symbol of each model and the detection valve opening and closing state can be referred to as a coordinated operation.
(3) When the compressed air is sent to the cylinder for leak compression inspection, the surrounding environment should be kept quiet, and the air supply pipeline, joints and air bags should be free of leakage.
(4) If the model to be tested is a diesel engine, consider using the old injector to remove the core parts. After a slight modification, it is used as a special joint for conveying compressed air.
(5) After checking the corresponding fault location, the corresponding technical requirements of the vehicle repair should be followed to carry out corresponding troubleshooting and repair work to restore the specific working performance of the engine.
(Continued from page 46) (4) Air, fuel, and lubricating oil should be clean and free of impurities. The lubricating oil should be of 15W40CD type.
(5) The turbocharger should be pre-lubricated when it is shut down for more than one week. Method: Disassemble the inlet pipe and the inlet pipe joint, inject 50ml of lubricating oil, and pay attention to turning the impeller while refueling, so that the supercharger can be fully lubricated before running.
(6) When the engine starts, idling for 2 to 3 minutes, so that the oil pressure and temperature are normal and then loaded, otherwise the bearing will be burnt due to lack of oil.
(7) When the engine is running at full temperature, there is no special situation and it is not allowed to stop immediately. It should be gradually reduced speed. At least idle for 2 to 3 minutes before stopping, prevent the supercharger from overheating and damage the supercharger due to inertia.
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