1. Determining the fault location that causes the cylinder pressure of the internal combustion engine to be insufficient Insufficient cylinder pressure in internal combustion engines usually shows that the internal combustion engine is not easy to start, work is weak, power is reduced, fuel consumption is increased, and black smoke or white smoke is emitted. The parts causing the cylinder pressure of the internal combustion engine are insufficient: the cylinder head ablation, the valve closing is not strict, the piston ring helium, the cylinder liner and the piston ring are worn out. So, how to use compressed air to determine the specific part of the fault? The method and the steps are: turning the piston of the cylinder to be tested to the compression top dead center; hanging the transmission to the high gear or using the hand brake, and if the machine is equipped with a torque converter, the crowbar can be used to clamp the starting ring gear. The crankshaft could not be rotated; the injector was removed and 0.8 MPa of compressed air was introduced from the mounting holes. Then, observe the possible phenomenon: if the air bubble in the radiator (water tank), the cylinder block and the cylinder head joint part leak out, indicating that the cylinder head gasket is ablated, the cylinder head gasket should be replaced; if the intake manifold and the exhaust pipe The manifold leaks outward, indicating that the valve is not tightly closed. The valve or valve seat should be ground or replaced, or the valve clearance should be re-adjusted. If the oil hole from the oil pan and the oil dip hole are out of the air, the piston ring is severe. If the helium or wear is too much, it may be that the piston ring is broken, the piston's bank is broken, and the cylinder liner is worn. The piston should be taken out for inspection. 2. Check the cylinder block for cracks After the internal combustion engine is overhauled or the cylinder liner is replaced, the cylinder block should be inspected for cracks, leaks, etc. In the absence of special tools and equipment, the use of compressed air for inspection is a simple, convenient and accurate means. First, use a rubber plate with a thickness of 10mm to make a special cylinder head gasket (same as 3 cylinder head gaskets), only remove the bolt holes and cylinder sleeve holes; then use a seamless steel pipe with a diameter of 22mm to cut the cylindrical sleeve of 130mm. (The quantity is determined according to the model); fill the water channel with water, install the self-made rubber cylinder head gasket, and then install the old cylinder head gasket. Each cylinder head bolt is sleeved with a cylindrical sleeve and tightened with a nut; 0.5~0.7 The compressed air of MPa is input from the water discharge switch on the body. Then, observe whether there is leakage or the like around the inside and outside of the machine and around the cylinder liner. 3. Check the performance of the power shift transmission The repaired power shift transmission can be tested for operational performance with compressed air prior to installation. After the transmission is assembled, the shift valve is not installed temporarily; the piston cylinders are filled with the allowed oil; the air pipes are sequentially docked with the oil passages, and compressed air of 0.6 to 0.8 MPa is input, at the moment of ventilation. The movement of the piston under test can be seen, or the sound of a "beep" can be heard when the piston is in contact, and the output shaft should not be able to rotate. After stopping the ventilation, the piston should be able to automatically return to the position without any stuck. If the output shaft can rotate, it can be determined that the block is normal, otherwise the repair is unsuccessful. 4. Check the performance of the hydraulic motor The structure of the hydraulic motor is relatively complicated, and there are many assembly points. If you pay little attention during the repair process, the motor may not work or work weakly; if the machine is installed without performance test, it is easy to rework. The assembled hydraulic motor is fixed on the workbench, and the working fluid that is allowed to be used is injected into the motor; after the compressed air of 0.6-0.8 MPa is input from an oil port, the output shaft of the hydraulic motor should be able to rotate at a constant speed without a card. There is no turbulence or turbulence, and the input of compressed air to another port should be rotated in the opposite direction. In this case, the motor can be considered to be working properly. 5. Check the leaks of various radiators (water tanks) Clean the sludge and dust on the surface of the radiator (water tank), temporarily block the pipe joint of the radiator (water tank) with a wooden plug; immerse the entire radiator in the water tank, and only expose the other pipe joint to the water surface; 0.3 The compressed air of ~0.5MPa is input into the radiator (water tank) through the pipe joint exposed to the water surface; observe whether there is any bubble in the radiator, if any, it is leaking, after being marked, taken out, welded or glued repair. 6. Disassemble rusted disc brakes The effect of pressing out the rusted caliper disc brake with compressed air is very obvious. After the clamp is removed, tighten the vent screw and fill the brake fluid from the inlet port, input 0.6~0.8MPa. The compressed air can press the piston out. Since the tension of each piston is different, the piston that is first pressed out should not be rushed out, and the brake fluid should be replenished and then compressed with compressed air until the two pistons can be taken out. 7. Check the performance of the gas-liquid master pump Fix the repaired gas-liquid master pump on the test bench, and install a pressure gauge with a range of 15 MPa at the outlet of the air pump; fill the fuel tank with brake fluid and discharge the air in the brake pump: At the inlet of the air pump, input 0.8 MPa of compressed air for 2 min. If the pressure drop of the pressure gauge is not more than 0.05 MPa and there is no leakage, the pointer of the pressure gauge refers to the range of 12 to 13 MPa, and the gas piston can quickly return to the position, which is qualified. 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Checking for mechanical failure with compressed air