The engine won't catch fire, which is one of the most common faults of cars. There are two situations when there is no fire: one is that the starting sound of the starter can be heard, but the engine can't start. The other is that there is no sound after turning the key.
The first case is that the starter is working, but the engine is not working. This situation is more complicated because it may be caused by one of many faults.
It is rare that two or more faults occur at the same time, but it cannot be said absolutely.
(1) may be a circuit or electronic fault at first. Here's the thing.
Unexpectedly, without warning. Circuit faults include: fuse blown, high-voltage coil disconnected, low-voltage circuit disconnected, central ignition wire falling off, distributor leakage, and spark plug damaged. Electronic failure mainly refers to the loss of function of the central computer control panel.
(2) Then there is the oil circuit failure. Oil circuit failure leads to flameout.
There are often signs that the engine is weak and the accelerator is stepping on cotton. The possible parts of oil circuit failure are: oil pump failure, oil circuit blockage, oil filter blockage, carburetor failure, nozzle damage and so on. Sometimes it happens that the fuel tank is empty and the owner doesn't know. Adding a few liters of gasoline will solve all the problems.
(3) Finally, it may be a mechanical failure. Common mechanical faults are: broken timing belt (chain), no pressure leakage of cylinder, etc.
The second situation is that even the starter doesn't work or barely works. The first thing to check at this time is the battery or battery. There are many ways to check, and it is best to have a voltmeter at hand. Connect the positive and negative poles of the battery, and then turn the key to ignite. If the voltage indicator suddenly drops below 8 volts at the moment when the power supply is turned on, it must be something wrong with your battery. There is no harm in not having a voltmeter. You can use a 12 volt light bulb and a short power cord instead. The method is the same. If the light bulb suddenly darkens obviously, it also indicates that the battery is aging. In many cases, the battery has failed, but the headlights can still be lit. This is not surprising. Only when you ask at the moment of ignition can you really test the performance of the battery. Because it's the most loaded at this time.
There is also a simple method: look at the outer wall of the battery with the naked eye. If expansion deformation is found, it means that it is absolutely necessary to replace the battery. The reason why the starter doesn't work is that the ignition switch is damaged, the ignition relay is damaged or the starter itself is damaged. In addition, check the grounding wire and fuse.
Case of automobile air conditioning failure
Case 1: the air conditioning output of Buick GS passenger car is abnormal.
Phenomenon: During the driving process of a Shanghai GM Buick GS passenger car, the cold air output from the air conditioning outlet gradually decreases.
Small, it will return to normal after a while.
Troubleshooting: First, let the air conditioning system work. After a period of time, the intermittent cooling described by the customer did occur.
The fault phenomenon of. When the cooling capacity drops, the working condition of the compressor is observed, and it is found that the compressor can always suck in. connect
Good air conditioning pressure gauge, test the high and low pressure end pressure in the system, and the value is normal. Use the special vehicle detector TECH2 to enter.
Line detection, no fault code storage, reading air conditioning data flow in ECU, no abnormality found.
After asking the owner, I learned that some time ago, the car added refrigerant to the repair shop outside, because the air conditioner was not cold, so I was pregnant.
It is suspected that the refrigerant purity of the car is not enough. After testing the refrigerant composition with the refrigerant purity analyzer, it is found that the system has 28 0 10.
R 12. Because the refrigerant added to the air conditioning system of Buick passenger car should be R 134a, the refrigerant in the system is discharged more.
Replace the compressor pressure regulating valve, clean the air conditioning pipeline with nitrogen, vacuumize, fill with pure R 134a refrigerant, and then call.
Turn on the air conditioning test and troubleshoot.
Fault analysis: Buick car is equipped with variable displacement air conditioning compressor. When the air conditioning system works, the air conditioning control system does not use it.
The temperature signal at the evaporator outlet is collected, but the compression ratio of the compressor is controlled according to the pressure change signal in the air conditioning pipeline.
Dynamically adjust the air outlet temperature. In the whole refrigeration process, the compressor is always running, and the adjustment of refrigeration intensity depends entirely on it.
The pressure regulating valve installed inside the compressor is used for control. When the pressure at the high pressure end of the air conditioning pipeline is too high, the pressure regulating valve is shortened.
The piston stroke in the compressor reduces the compression ratio and reduces the refrigeration intensity. When the pressure at the high pressure end drops to a certain range
When the pressure at the low pressure end rises to a certain extent, the pressure regulating valve increases the piston stroke and improves the refrigeration intensity. Because this car
R 12 is mixed in the refrigerant of air conditioning system, which leads to poor pressure control of the system and increased refrigeration intensity. Working in this state
After a period of time, the outer wall of the evaporator was frosted due to the low temperature, and the air outlet of the air conditioner was windless. When the frost on the outer wall of the evaporator melts, it will freeze.
The system is back to normal. Because the low temperature changes the elastic coefficient of the internal spring of the pressure regulating valve, the pressure regulation
Valves should also be replaced. During the daily maintenance of air conditioners, it is often found that the wrong refrigerant is added, which is more common in the 1990s.
Longer imported cars are more common. Maintenance personnel must ensure that the vehicle uses refrigerant before filling air conditioning refrigerant.
Type, so as not to cause serious consequences.
Case 2: Audi 100 air conditioner is not cold.
Phenomenon: The air conditioner of an Audi 100 2.6E car is not cold.
Troubleshooting: After checking the normal operation of the automobile air conditioner compressor, touch your cold hand on the low-pressure pipe of the air conditioner with your hand and say
The refrigeration system of Ming air conditioning works normally, but the wind blown out of the air outlet is not cold. Adjust the temperature of the air conditioning control panel to.
18℃ or the lowest and in the internal circulation state, the air conditioner is still not cold. Because the car is equipped with automatic air conditioning, which is different from the manual air conditioning area.
The difference is that the conversion between the cold and warm air doors and the air duct doors of each air outlet is controlled by an electric servo mechanism. Refer to Manual Air Conditioning Inspection.
Train of thought, when checking the cold and warm air door of automatic air conditioner, it is found that the temperature of the control panel is adjusted from hot (H) to cold (L) or from
When the cold air door is switched to the hot air door, the electric servo mechanism that controls the change of the cold air door will never move. Because the damper is in the warm air position at this time, so
So that cold air will not be blown out of the air duct directly through the evaporator, but will pass through the warm air radiator, so that the blown air will not
Cool. So the electric servo mechanism was removed for inspection, and it was found that the adjusting motor was damaged.
After replacing the electric servo mechanism, the temperature was adjusted, the cold and warm air doors were switched to normal, the cold air of the air conditioner returned to normal, and the fault occurred.
Rule out.
There are many possibilities for relay failure:
Due to excessive current, the contacts were burnt out.
The coil voltage is unstable, or the coil is aging and melting.
Or contact aging, poor contact.
There are many situations, and the specific situation is analyzed.
Misfire refers to the inability of the engine ignition system to effectively release the ignition energy in the cylinder (ignition failure), fuel injection deviation (mixture concentration deviation), low cylinder compression pressure or any other reasons, which leads to the inability to interrupt or burn the combustion process in the cylinder, resulting in excessive emissions or damage to the catalyst due to overheating. In terms of OBD diagnosis and detection, this means that the number of misfires exceeds the limit value, and the system judges that the misfire fault has occurred. 1, idle jitter 2, weak acceleration 3, increased fuel consumption 4, and excessive emissions.
The case study of multi-cylinder misfire maintenance method shows that misfire refers to the failure of engine ignition system to effectively release in-cylinder ignition energy (ignition failure), fuel injection deviation (mixture concentration deviation), too low cylinder compression pressure or any other reasons, which leads to in-cylinder combustion process can not be interrupted or burned, resulting in excessive emissions or damage to catalyst due to overheating. In terms of OBD diagnosis and detection, this means that the number of misfires exceeds the limit value, and the system judges that the misfire fault has occurred. Conditions for running DTC engine speed 600; When the engine load at -28℃ is greater than zero load, the engine runs in a stable state, that is, the change rates of throttle, load and ignition advance angle are within a certain range; The vehicle is driving on a non-bad road, that is, the fire detection function is running at this time; No related sensor failure; The engine is in a non-fuel cut-off state; Actions that occur when the DTC is set If the corresponding degree of misfire is completely detected in two consecutive driving cycles, the fault indicator will light up and the fault indicator will flash. The following operations will be prohibited: self-learning of misfire fuel supply, self-learning of misfire fuel cut-off, closed-loop control of post-oxygen, fault phenomena related to catalyst diagnosis: 1, idling jitter 2, weak acceleration 3, increased fuel consumption 4, and excessive emissions.
Check steps: Step by step operation 1 Let the vehicle stand for a certain period of time to cool the engine water temperature and oil temperature to room temperature or lower. 2 Dismantle the catalytic converter, observe whether the carrier is sintered, and reinstall the original catalytic converter. Whether there is a serious fire in the Step 3 Step 4 3 system, rather than an accidental fire or misjudgment. Step 4 4 Check the engine ignition system. Observe whether the connection between the ignition high-voltage line of each cylinder and the spark plug and the ignition coil is loose, and whether the ignition high-voltage line and the ignition coil connector are damaged, aged or short-circuited with the body and engine; Remove the spark plug, and observe whether there is oil stain, blackening and carbon deposit on the electrode, and whether the spark plug gap is normal (the spark plug must be consistent with the original specifications). The above phenomenon may lead to fire problems. (Refer to the ignition system fault inspection method). Step five, step nine
5 Replace the above parts related to ignition system failure. Step 6 6 Start the engine and observe whether the engine runs smoothly at idle speed. Step 7 Step 9 7 Turn off the engine, turn the ignition switch to the "on" state, connect the scan tool, and clear the relevant fault codes. Eight different methods can be used to simply judge whether the vehicle is still on fire. Read the frozen frame recorded during the fire from the fault diagnosis instrument, drive the vehicle under the same working condition according to the relevant information, and observe whether the fire phenomenon reappears; The vehicle accelerates evenly from idle speed to third gear at 4000 rpm, and observe whether there is obvious ignition jitter during acceleration; The vehicle runs on a flat road at a constant speed for a period of time (different gears and speeds), and observe whether the fault light flashes; If there is no flashing, turn off the engine, disconnect the main relay of the system and restart the engine. Drive on a stable road (different gears and speeds) for a period of time, and observe whether the fault light is on. Step 9 Step 14 9 The vehicle fire was not caused by the ignition system, but may be caused by the failure of the fuel injection system. 10 Check the oil pressure of the injector and the system (refer to the system oil pressure inspection method). If it is normal, check whether the steam filter and oil pump are normal. Step 13 Step111misfire is caused by engine oil circuit failure. Replace related faulty parts. Step 12 12 Repeat the inspection method in step 8 to see if the fault light is on or flashing. Step 13 Step 14 13 Engine fire is not caused by oil circuit failure, so it is necessary to check the mechanical state of the engine. 14 If the original catalyst is sintered, replace the damaged catalyst. Install clean gasoline nozzle.