1. Avoid only adding oil without changing it

机油在柴油机的使用中是必不可少的，主要起润滑、清洁等作用。因此，很多驾驶员都会注意检查润滑油的油量，并按标准添加，但是却忽视了润滑油质量的检查和对已经变质机油的更换，导致一些发动机的运动机件总是在较差的润滑环境中运转，从而加速各机件的磨损。在正常情况下机油的损耗并不大，但是却很容易污染，从而失去保护柴油机的作用。在柴油机运转过程中，许多污物(燃油不完全燃烧生成的碳烟、积炭和积垢等)都会进入到机油中。对于新的或大修后的机械，试运转之后杂质会更多，如果只加不换就急于投入使用，很容易引起烧瓦、抱轴等意外事故。另外，即使更换机油，某些驾驶员由于缺乏维修经验或者图省事，也会在更换时不完全清洗油道，使机械杂质仍然残留在油底壳及油路中。

Engine oil is essential in the use of diesel engine, mainly for lubrication and cleaning. Therefore, many drivers pay attention to check the oil quantity of lubricating oil and add it according to the standard, but ignore the inspection of lubricating oil quality and the replacement of deteriorated oil, resulting in some moving parts of the engine always running in a poor lubrication environment, so as to accelerate the wear of various parts. Under normal circumstances, the loss of engine oil is not large, but it is easy to pollute, thus losing the role of protecting the diesel engine. During the operation of diesel engine, a lot of dirt (soot, carbon and dirt generated by incomplete combustion of fuel) will enter the engine oil. For new or overhauled machinery, there will be more impurities after commissioning. If it is only added but not replaced, it is eager to be put into use, which is easy to cause accidents such as tile burning and shaft holding. In addition, even if the engine oil is changed, some drivers will not completely clean the oil passage during replacement due to lack of maintenance experience or easy work, so that mechanical impurities remain in the oil pan and oil circuit.

2、忌黄油乱用乱涂

2. Do not use butter indiscriminately

黄油是工程机械修理中常用的润滑脂，可起到润滑和密封的作用。因此，有些修理工在安装汽缸垫时，就会在汽缸垫上涂上一层黄油，认为这样可以增加柴油机的密封性。但这样做反而影响了柴油机的工作性能。汽缸垫是柴油机缸体与缸盖之间重要的密封件，它不但能密封汽缸内所产生的高温高压气体，而且还能密封汽缸盖和缸体内的水和润滑油，所以在拆装汽缸垫时，都要特别注意它的密封质量。如果安装时在汽缸垫上涂黄油，当汽缸盖螺栓拧紧时，一部分黄油就会被挤压到汽缸水道和油道中，留在缸垫间的黄油在汽缸工作时，由于受高温影响，一部分会流入汽缸燃烧，另一部分则残留在缸体与缸盖的结合面上，使缸垫、缸盖与机体平面之间产生空隙，高温高压燃气很容易从此处冲击汽缸垫，毁坏缸垫，造成漏气。另外就是轮胎螺母黄油，因为轮胎螺母拧紧后，螺纹间就具有自锁的特征。这是由于螺纹螺旋角小于螺纹间的当量摩擦角的缘故。给定的螺栓联接中，螺旋升角是一定值，而当量摩擦角则随螺纹间的摩擦状态而变。显然，涂油后螺纹间的当量摩擦角减小，螺栓联接的自锁性能变差。因此在轮胎的螺栓和螺母上不要涂润滑脂或滴上润滑油。这样做，反而会使螺母松动，甚至酿成事故。

Grease is commonly used in the repair of construction machinery, which can play the role of lubrication and sealing. Therefore, some repairmen will apply a layer of grease on the cylinder gasket when installing the cylinder gasket, believing that this can increase the tightness of the diesel engine. However, this will affect the working performance of the diesel engine. Cylinder gasket is an important seal between diesel engine cylinder block and cylinder head. It can not only seal the high-temperature and high-pressure gas generated in the cylinder, but also seal the water and lubricating oil in the cylinder head and cylinder body. Therefore, special attention should be paid to its sealing quality when disassembling the cylinder gasket. If the cylinder gasket is coated with butter during installation, when the cylinder head bolts are tightened, part of the butter will be squeezed into the cylinder water channel and oil channel. When the cylinder is working, due to the influence of high temperature, part of the butter left between the cylinder gasket will flow into the cylinder for combustion, and the other part will remain on the joint surface of the cylinder block and cylinder head, resulting in a gap between the cylinder gasket, cylinder head and engine body plane, High temperature and high pressure gas can easily impact the cylinder gasket from here, destroy the cylinder gasket and cause air leakage. The other is the tire nut butter, because after the tire nut is tightened, the threads have the feature of self-locking. This is because the helix angle of the thread is less than the equivalent friction angle between the threads. In a given bolt connection, the spiral rise angle is a certain value, and the equivalent friction angle changes with the friction state between threads. Obviously, the equivalent friction angle between threads decreases after oiling, and the self-locking performance of bolt connection becomes worse. Therefore, do not apply grease or drop lubricating oil on the bolts and nuts of the tire. Doing so will loosen the nut and even cause accidents.

3、忌缸套和活塞新品不经选配即安装

3. Do not install new cylinder liners and pistons without selection

在换装汽缸套和活塞时，认为新的汽缸套和活塞都是标准件，都具有互换性，装上去就可以使用了。实际上，汽缸套与活塞的尺寸都有一定的公差范围。如把大尺寸的汽缸套配上小尺寸的活塞，会使配合间隙过大，造成压缩无力，启动困难。因此，换装时须检查标准缸套与活塞的尺寸分组代号，装用的缸套和活塞须使标准活塞的尺寸分组代号与标准缸套的尺寸分组代号相同，只有这样才能保证两者之间具有标准的配合间隙。另外，各缸装用同一分组代号的缸套和活塞的同时，还要注意装前检验缸塞间隙，为了保证装配标准，在装机前还应进行一次检测，以防装上假冒伪劣的残次产品。

When replacing the cylinder liner and piston, it is considered that the new cylinder liner and piston are standard parts and interchangeable, so they can be used after installation. In fact, the dimensions of cylinder liner and piston have a certain tolerance range. If the large cylinder liner is matched with the small piston, the matching clearance will be too large, resulting in weak compression and difficult start. Therefore, the size grouping code of standard cylinder liner and piston must be checked during replacement. The installed cylinder liner and piston must make the size grouping code of standard piston the same as that of standard cylinder liner. Only in this way can we ensure that there is a standard fit clearance between them. In addition, while installing cylinder liners and pistons with the same group code, pay attention to the inspection of cylinder plug clearance before installation. In order to ensure the assembly standard, a test shall be carried out before installation to prevent the installation of fake and inferior defective products.

4、忌不检查柱塞行程余量

4. Do not check the plunger stroke allowance

在柱塞式喷油泵的调试中，很多的维修人员不注意检查柱塞的行程余量。所谓柱塞的行程余量，是指柱塞被凸轮轴上的凸轮顶至上止点后，还能继续上行的移动量。调好供油开始时间后，之所以还要检查行程余量，是因为柱塞的行程余量与柱塞、套筒的磨损有关。柱塞与套筒磨损后，柱塞要往上多运动一段才能开始供油，从而使供油开始时间推迟。当拧出调整螺栓或换用较厚的调整垫块、垫片后，柱塞的较低位置上移，使柱塞的行程余量减小。所以，在维修调试喷油泵时，首先应检查此行程余量，以判定喷油泵是否还允许调整。检查时，应根据喷油泵的不同结构采用下述不同方法：a)转动凸轮轴，将柱塞顶至上止点后，拆下出油阀及阀座，用深游标尺测量。

In the commissioning of plunger fuel injection pump, many maintenance personnel do not pay attention to checking the stroke margin of plunger. The so-called stroke margin of the plunger refers to the amount of upward movement of the plunger after it is pushed to the top dead center by the cam on the camshaft. After adjusting the oil supply start time, the reason why the travel allowance should be checked is that the travel allowance of the plunger is related to the wear of the plunger and sleeve. After the plunger and sleeve are worn, the plunger needs to move upward for a long time to start oil supply, so as to delay the start time of oil supply. When the adjusting bolt is screwed out or the thicker adjusting cushion block and gasket are replaced, the lower position of the plunger moves upward to reduce the stroke allowance of the plunger. Therefore, when maintaining and debugging the fuel injection pump, first check the stroke margin to determine whether the fuel injection pump is still allowed to be adjusted. During inspection, the following methods shall be adopted according to different structures of the fuel injection pump: a) rotate the camshaft, push the plunger to the top dead center, remove the oil outlet valve and valve seat, and measure with a deep travel ruler.

5、忌汽缸间隙测量不准

5. Avoid inaccurate cylinder clearance measurement

在测量汽缸间隙时，未能在活塞裙部垂直于活塞销孔的方向测量，而在其它方向测量。铝合金活塞的结构特点是上小下大，为一锥体，且局部断面为椭圆形，所以沿圆周方向的气缸间隙并不相等。测量时，规定以椭圆长轴方向的间隙为准，即测量活塞裙部垂直于活塞销孔方向的间隙。这样测量比较方便、准确，而且在往复运动中，活塞裙部垂直于活塞销孔的方向因受侧向压力的作用而磨损较大，所以，测量汽缸间隙时，应在活塞裙部垂直于活塞销孔的方向测量。

When measuring the cylinder clearance, it cannot be measured in the direction of the piston skirt perpendicular to the piston pin hole, but in other directions. The structural feature of aluminum alloy piston is that the upper part is small and the lower part is large, which is a cone, and the local section is oval, so the cylinder clearance along the circumferential direction is not equal. During measurement, the clearance in the direction of the long axis of the ellipse shall prevail, that is, the clearance of the piston skirt perpendicular to the piston pin hole shall be measured. This measurement is more convenient and accurate, and in reciprocating motion, the direction of the piston skirt perpendicular to the piston pin hole is greatly worn due to the action of lateral pressure. Therefore, when measuring the cylinder clearance, it should be measured in the direction of the piston skirt perpendicular to the piston pin hole.

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