Automobile fault diagnosis
After the automobile is manufactured and used, it will inevitably break down for various reasons, thus changing the power, economy, handling stability and use safety of the automobile. Some car failures are sudden, and some are gradually formed. When a car breaks down, it can accurately and quickly diagnose the cause of the fault, find out the damaged parts and eliminate the fault as soon as possible with experience and scientific knowledge, which is beneficial to the use and maintenance of the car.
As a modern means of transportation, the automobile has a certain life from the date of manufacture. No matter how you use it, it will break down sooner or later, so it is relative not to break down in use, and it is inevitable that various failures will occur. Therefore, the analysis and diagnosis of the fault causes are conducive to making judgments and making the car run in a good technical state.
(A) the cause of the car failure
The main causes of automobile failure are:
1. has its own fragile parts.
In automobile design, it is impossible to make all parts of an automobile have the same life. Some parts of the car itself are wearing parts, such as air filter, spark plug, engine oil, etc., which have a short service life and need to be replaced regularly. If it is not replaced in time or damaged in advance, the car will break down.
2. The quality difference of the parts themselves
Cars and auto parts are produced in large quantities by different manufacturers, and there are inevitably quality differences. There will be problems in the use of original accessories, especially when cooperative factories and unqualified accessories are installed on cars, so all automobile manufacturers are trying to improve the quality of accessories and eliminate the quality defects of accessories themselves.
3. Quality differences of automobile consumables
Consumables on automobiles mainly include fuel oil and lubricating oil. The poor quality of these additives will seriously affect the performance and service life of automobiles and make automobiles more prone to failure. However, it is often difficult for users to ensure that these supplies are added. Accidentally adding inferior gasoline and lubricating oil will do great harm to cars and engines. Maybe the user hasn't paid attention to it, and the car has a problem.
4. The car environment has an impact.
Cars used in the open air have a great impact on the environment. Expressway pavement is wide and flat with high speed, which is prone to faults and accidents; The road surface is uneven, the car vibrates badly and is easy to be damaged. Large power consumption in mountainous areas and long waiting time in cities have greatly changed the working conditions of cars. Sometimes, when they can't adapt, they are easy to fail or get hurt suddenly.
5. The influence of driving skills and driving methods
Driving technology has a great influence on automobile faults, especially improper use. Poor use and management of cars, failure to carry out running-in and regular maintenance according to regulations, and rough starting and driving will all cause early damage and failure of cars.
6. The influence of automobile fault diagnosis technology and maintenance technology
The car should be maintained regularly in use, and the fault can be diagnosed accurately before it can be repaired. The use, maintenance, fault diagnosis and maintenance of automobiles all need technology, especially the wide application of modern automobiles and high technology, which requires automobile users and maintenance workers to understand and master automobile technology and advanced new technology. If you can't fix it, you can't fix it, and if you don't understand it, you can't move it, so as to avoid old diseases and new problems.
Therefore, automobile faults widely exist in the whole process of automobile manufacturing, use, maintenance and repair, and every link should be highly valued, especially in automobile use, and faults should be found and eliminated in time to reduce accidents in automobile use.
(2) Common automobile faults
The common faults of automobiles can be judged by the abnormal performance and appearance symptoms of automobiles caused by experience, senses and instruments. Common faults mainly include:
1. Abnormal automobile performance
Abnormal automobile performance is the poor power and economy of the automobile, which mainly shows that the maximum driving speed of the automobile is obviously low and the acceleration performance is poor; Cars consume a lot of fuel and oil. The ride comfort of the car is poor, and the vibration and noise of the car are obviously increased. The vehicle handling stability is poor, the vehicle is easy to run off, and the front of the vehicle shimmies; Brake deviation, long braking distance or no braking, etc.
2. Abnormal working conditions of automobiles
Some abnormal phenomena suddenly appear in the process of using the car, which should be prevented: the engine suddenly shuts down while driving; When the brakes are needed, the car has no brakes; This car won't start in winter; The engine cannot be started after flameout; Sudden steering failure during driving; What's more, the car has a flat tire and the car spontaneously ignites. The symptoms are obvious and the cause is complicated. The main reason is that the failure in the car is ignored and develops into sudden damage.
3. Abnormal noise of cars
When a car breaks down in use, it is often the easiest to show it in the form of abnormal noise. Under normal circumstances, drivers and passengers can hear it. Experienced people can judge automobile faults according to the location where abnormal noises occur and the different frequencies and timbres of sounds. Generally, the noise is dull and accompanied by strong chattering noise, so the fault is more serious. You should stop the car, reduce the engine speed or turn off the engine to find it. Some sounds are caused by the failure of some parts, which does not affect the use of the car and cannot be found for the time being. You can drive your car back to the base or to the nearby auto repair department and ask experienced personnel to find it.
4. Car smell
Odor is the most taboo when a car is driving. People's sense of smell is very sensitive, and they will smell it as soon as there is an odor. If there is an odor, we must first judge whether it is the odor in the car or the odor in the surrounding environment. Automobile odor mainly includes the coke smell from non-metallic friction materials on brakes and clutches; Special odor of battery electrolyte; The burning smell of automobile electrical systems and wires. Be sure to pay full attention to the smell of burning engine oil and abnormal gasoline smell at some time.
5. The car is overheated.
Automobile overheating is characterized by the temperature of all parts of the automobile exceeding the normal use temperature range. The engine is overheated, especially when the radiator is boiling. Transmission overheating, rear axle housing overheating and brake overheating can be indicated by manual or water test. Vehicle overheating needs further inspection to find out the root cause of the failure. If it is caused by long-term high load, it will generally not affect the use. If the internal mechanism fails, it should be diagnosed and eliminated in time.
6. Abnormal exhaust smoke color
The smoke color of engine exhaust is the appearance of engine work. There is a certain smoke color when the engine is burning normally, and it changes when the engine is not working normally. The engine oil burning waste gas is blue, indicating that the engine needs maintenance; The exhaust gas from incomplete combustion of the engine is black, so the fuel should be replaced or the ignition timing should be adjusted; The engine exhaust is white, indicating that there is water in the fuel or in the cylinder. Check the fuel or engine.
7. Car leakage
Automobile leakage is manifested as fuel leakage, engine oil leakage, coolant leakage, brake fluid leakage, steering oil leakage, lubricating oil leakage and refrigerant leakage, as well as battery leakage and electrical system leakage. Automobile air leakage is easy to cause automobile overheating and mechanism damage. If the steering oil leaks, it is easy to cause the steering failure of the car; Brake fluid leakage is easy to cause brake failure.
The appearance of this car is abnormal.
When the car is parked on the flat ground, it is sometimes found that the car is skewed vertically or horizontally when the appearance is checked, which is characterized by abnormal appearance. Should pay attention to check the tire pressure, frame and suspension damage, body damage and other anomalies. Abnormal car appearance may affect the use of the car. For example, the center of gravity of the car deviates, the vibration is serious, the steering is unstable, and the car deviates.
9. Abnormal car driving
The abnormal driving performance of the car is that the car can't accelerate, turn and brake according to the driver's wishes, and the faults of the control mechanism and executive mechanism of the car can be detected. Besides checking and adjusting the accelerator pedal, brake pedal, clutch pedal, steering wheel and its transmission mechanism, the automobile should also be inspected comprehensively. Find out the fault and use it after normal maintenance.
(3) Automobile fault diagnosis
In the process of using a car, it is inevitable that there will be various failures. When the car breaks down on the way, the driver must check, diagnose and eliminate the fault on the spot before the car can continue driving. Some faults are relatively large or complicated, and it is difficult for drivers to solve them themselves. It is checked, diagnosed and eliminated by automobile mechanics and automobile maintenance engineers and technicians. There are many kinds of automobile faults, but the methods and steps of fault diagnosis are certain. As long as the basic method is correct, the thinking is clear and the method is proper, the fault diagnosis is easy to make.
The methods of automobile fault diagnosis can basically be summarized as 12: looking, watching, listening, measuring, touching, smelling, changing, measuring, sectional inspection and partial disassembly.
The application of these methods should be guided by theory; Fully understand the use and maintenance of the car, fully understand the occurrence of faults. For the simple faults in the car, the reason and location can be found only by experience and feeling; Difficult faults can only be found by instruments and special fault diagnosis equipment. With the equipment, you should also be able to use it. In use, you should combine the maintenance experience, flexibly use these fault diagnosis methods, and make a comprehensive evaluation of the fault. Practice in diagnosis, sum up accumulated experience and apply it freely.
Second, the automobile fault diagnosis method
(1) Diagnose the fault by looking at the problem.
Doctors need to "look, listen and ask questions" when they see a doctor, and so does automobile fault diagnosis, among which looking and asking questions are effective methods for quickly diagnosing automobile faults.
When a car breaks down, it needs to be diagnosed. When a mechanic sees a car for the first time, it is very important to make a preliminary judgment on the shape and service life of the car, so as to know the shape of the car from the appearance. The service life can be judged by exposing the engine or flipping the cab from the appearance, and experienced maintenance personnel can even judge the car fault at once.
When the car needs to be repaired, the maintenance personnel must ask the user and the owner clearly, including the model, service life, maintenance, service, the location and phenomenon of the fault, and what inspections and maintenance have been done after the fault, so as to understand the fault as deeply as possible. This is a shortcut.
Knowing the form can reflect the basic structure and performance of the car. If we know the form and structure of the car and have rich maintenance experience, then the diagnosis will be easier. If you don't know enough, you can master it by looking up books and materials.
Through in-depth inquiry, you can basically know where the fault occurred. For example, you can ask whether the fault occurred in the engine or the transmission; If it is an engine, we can further understand whether it is an electrical fault or a mechanical fault; If it is a mechanical fault, we can know whether it is a crank-connecting rod mechanism or a valve train, so it is much easier to make further diagnosis. After the fault is determined, it is easy to eliminate and maintain.
If the user wants to overhaul the car, he should also ask about repairing the engine powertrain, repairing the car chassis, repairing the car cab and body, repairing the car electrical appliances and air conditioning. Which parts and assemblies are the focus of maintenance, etc. , so as to determine the maintenance plan.
(2) Diagnose the fault by empirical method.
As the name implies, the empirical method of fault diagnosis is based on the basic quality and rich experience of drivers and maintenance personnel to diagnose automobile faults quickly and accurately.
The so-called basic quality, whether drivers or car maintenance personnel, should learn from books and improve in practice, so as to obtain basic car knowledge and maintenance experience, which is very important. Automobile technology is a comprehensive embodiment of national economic development. Automobile technology is developing faster and faster, and there are more and more new technologies. Therefore, it is impossible to study hard from books and practice. For example, the single-pump oil supply speed regulation technology of automobile diesel engine and the new diesel engine technology abroad all need to learn books and materials on the basis of original knowledge in order to carry out the actual maintenance work. Only practice under the guidance of theory is correct practice, and experience can be summarized and accumulated in practice.
The so-called maintenance experience is also very important. With the experience of automobile maintenance, the same fault and similar fault can be solved at once. Personal experience, summing up accumulated experience; There are also experiences learned from books and other ways. Only by combining the two can we accumulate experience and judge automobile faults smoothly. For example, if the diesel engine is broken, the cab should be turned over. If the steering mechanism is stuck for a period of time, the cab cannot be turned over. Experienced people only need to push and pry, and the cab will turn over immediately. For example, when the diesel engine goes out of control, the speed of the diesel engine suddenly rises and the noise becomes louder and louder. Without experience, the diesel engine can't be turned off. Experienced people can turn the fuel change-over valve on the fuel tank by 45 degrees, and the diesel engine will shut down immediately, so as to avoid the occurrence of vicious accidents. It is not difficult to see that this is the result of accumulated experience. Therefore, we should constantly sum up experience, turn it into a powerful weapon for automobile maintenance, constantly arm ourselves with new knowledge and experience, and solve various even very complicated problems in automobiles with experience.
Look at the rest by yourself, and remember to give high marks next time.