1. Avoid adding engine oil without changing it
Engine oil is essential in the use of diesel engine. Its main functions are lubrication, cooling and cleaning. Therefore, many small concrete mixer drivers will pay attention to check the amount of lubricating oil, and add it according to the standard, but they ignore the inspection of the quality of lubricating oil and the timely replacement of the deteriorated engine oil, which leads to some engine moving parts always running in poor lubrication environment, accelerating the wear of the parts. Generally, the loss of engine oil is not great under normal conditions, but it is very easy to produce pollution and lose the function of protecting diesel engine. In the process of diesel engine operation, many pollutants (soot, carbon and scale formed by incomplete combustion of fuel) will enter into the engine oil. For new or overhauled machinery, there will be more impurities after commissioning. If it is put into use without replacement, it is easy to cause accidents such as tile burning and axle holding. In addition, even if the engine oil is changed, some drivers will not thoroughly clean the oil passage during the replacement due to lack of maintenance experience or convenience, so that mechanical impurities remain in the oil pan and oil circuit.
2. The new cylinder liner and piston should not be installed without matching
When replacing the cylinder liner and piston, it is considered that the new cylinder liner and piston are standard parts with interchangeability and can be used after being installed. In fact, there is a certain tolerance range for the dimensions of cylinder liner and piston. If the largest size of cylinder liner is matched with the smallest size of piston, the fit clearance will be too large, resulting in weak compression and difficult starting. Therefore, before the replacement of small concrete mixer, the dimension grouping code of standard cylinder liner and piston must be checked, and the dimension grouping code of standard piston must be the same as that of standard cylinder liner, so as to ensure the standard fit clearance between them. In addition, when cylinder liners and pistons with the same grouping code are installed in each cylinder, the clearance between cylinder and piston should be inspected before installation. In order to ensure the assembly standard, another inspection should be conducted before installation to prevent the installation of fake and inferior defective products.
3. Do not check the plunger stroke allowance of cement truck
In the debugging process of plunger type fuel injection pump, many maintenance personnel do not pay attention to check the stroke allowance of plunger. The so-called stroke allowance of the plunger refers to the amount of movement that the plunger can continue to move upward after being pushed to the top dead center by the cam on the camshaft. After adjusting the start time of oil supply for small concrete mixer, the reason for checking the stroke allowance is that the stroke allowance of plunger is related to the wear of plunger and sleeve.
After the plunger and sleeve are worn, the plunger can start to supply oil only after moving upward for a long time, which delays the start time of supply oil. When the adjusting bolt is screwed out or a thicker adjusting pad or gasket is replaced, the lowest position of the plunger will move up, which will reduce the stroke allowance of the plunger. Therefore, in the maintenance and debugging of the fuel injection pump, we should first check the stroke allowance to determine whether the fuel injection pump is still allowed to adjust. During the inspection, different methods should be adopted according to the different structures of the injection pump: a) turn the camshaft, push the plunger to the top dead center, remove the oil outlet valve and valve seat, and measure with the depth vernier. b) After the plunger is pushed to the top dead center, pry the spring seat of the plunger spring with a screwdriver to make the plunger rise to the highest point. Then insert a thickness gauge between the lower plane of the plunger and the tappet adjusting bolt for measurement. The allowance of plunger wear should not be less than 1.5mm after the standard stroke.
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