With the continuous maturity of domestic diagnostic technology, more and more maintenance personnel began to use the vacuum meter detection function for maintenance. Conventional pointer-type vacuum gauges have gradually been replaced by digital vacuum gauges due to factors such as large errors, easy damage, and difficulty in determining test results. Here, the application of the digital vacuum gauge in the diagnostic test is analyzed.
First, the advantages of the digital vacuum table 1, the measurement results accurate digital display vacuum table to display the measurement results, at a glance, no artificial reading error.
2, the measurement range of large digital vacuum gauges generally larger than the pointer vacuum gauge measurement range, usually 2 to 3 times the pointer type multimeter.
3, the overload capacity of the digital display vacuum table generally has a relatively complete protection circuit, generally does not damage the integrated circuit in the table.
4, the function is extended, the digital display vacuum table has a large-scale integrated circuit inside, and the digital display technology is adopted. Therefore, some new functions are expanded in the original test function, especially the online function of the computer, which will make the digital vacuum watch The intelligence aspect has been greatly enhanced.
Second, the digital vacuum gauge test method 1, before the test preparation In order to better use the digital vacuum gauge to diagnose the fault, the test must ensure that the ignition timing and idle limit values ​​are in the normal range, under this premise, any deviation The value of the normal vacuum indicates that the engine is faulty.
2. When determining the engine fault measurement according to different engine speeds, the vacuum of the vacuum gauge must be directly derived from the intake manifold, because only the vacuum of the intake manifold is directly derived from the vacuum of the engine. In order to distinguish the faults reflected by the vacuum values ​​under different working conditions, the vacuum degree of the engine intake manifold can be divided into three basic types: idle speed test, rapid acceleration test and exhaust system block test.
(1) Idle speed test When the engine is working normally, the value should be 50~70kPa measured by vacuum gauge under idle condition. If the measured value is not in this range, it should be analyzed according to different situations to determine the fault.
1 If the vacuum gauge value during the idle test is low and stable, the following checks should be made: check the initial ignition timing; check the valve timing; check the cylinder pressure; check the crankcase forced air control valve.
2 If the vacuum gauge value during the idle test is regularly decreased by 6~9kPa, the following checks should be made: check if there is a spark plug that is not working; check if there is a burnt valve (cylinder pressure test); check if there is burnout Piston (cylinder pressure test).
3 If the vacuum gauge value is found to fall irregularly to 10~27kPa, the following checks should be made: check the spark plug; find the stuck valve; look for the stuck valve lifter or hydraulic tappet.
4 If the vacuum gauge value is displayed slowly at 27~34kPa, the following work should be performed: check if the mixture is too rich; check if the spark plug gap is too small.
5 If the vacuum gauge pointer is displayed at 47~61kPa quickly when idling, the intake valve tappet and the pipe are worn and loose. If the vacuum gauge pointer is displayed slowly between 34 and 76 kPa, and the value jumps as the engine speed increases, the valve spring elasticity is insufficient.
6 If the value of the vacuum gauge is displayed back and forth between 18 and 65 kPa at idle, it is caused by air leakage from the cylinder liner.
7 If the engine idle speed is too high, the test manifold vacuum is less than 40 kPa, indicating that the manifold or the main pipe leaks after the throttle of the engine, and the leakage portion is generally a manifold pad and a plurality of pipes connected to the manifold. Such as vacuum booster air pipe and so on. When I was repairing a Mercedes 560SEL sedan, I used this method to detect the air leakage. I also used the elimination method to determine the fault location in the steering assist control valve. After the Zui, it was determined that the power supply fuse was controlled by the steering assist control valve. Troubleshoot after replacing the fuse.
8 If the engine is difficult to start, the stable idle speed cannot be guaranteed, and the vacuum of the test engine is above 50 kPa. It indicates that there is no problem in the intake pipe of the engine. The fault lies in poor ignition or poor fuel injection caused by the electronic control system, such as ignition coil failure.
(2) The rapid acceleration test is performed when the engine is rapidly accelerating, and the degree of leakage of the piston can also be displayed. When accelerating, the reading of the vacuum gauge should suddenly drop; when the speed is decelerated, the vacuum gauge value will jump up sharply at the original idle speed. That is, when the throttle is quickly opened and closed, the value of the vacuum gauge should fluctuate between 7 and 8 kPa.
1 If the piston leaks seriously, the swing amplitude of the vacuum gauge pointer will be less obvious. The wider the swing of the vacuum gauge pointer, the better the engine's technical condition.
2 If the value of the vacuum gauge is lower than the normal value when idling, the pointer will fall back to “0†when the acceleration is rapid, and the pointer cannot be raised to about 86 kPa when the throttle is suddenly closed. This phenomenon is mainly caused by air leakage from the piston ring and the intake pipe gasket.
(3) Exhaust system blocking test This test is carried out under the condition of engine speed of 1000r/min. Careful observation of the vacuum gauge reading, if the reading is gradually decreased gradually, indicates that the exhaust system is blocked.
It should be noted that the above values ​​are all measured at the height equivalent to sea level. We know that the intake manifold vacuum decreases with increasing altitude. Generally, for every 500m increase in altitude, the vacuum will be reduced by 5.5kPa. Therefore, when measuring the intake manifold vacuum, we should convert according to the altitude.
Third, the use of vacuum gauge to diagnose engine faults, combined with the diagnosis of fault cases to analyze the application of vacuum gauges in fault diagnosis.
1. When the idling speed is exhausted, the exhaust pipe emits black smoke. In 1996, the Krona sedan was produced. When the idling speed, the exhaust pipe emits black smoke, and the fuel consumption is large. When the acceleration is accelerated, the black smoke is larger and the idle speed is unstable. According to the fault phenomenon, it is basically judged that the mixed gas is too rich, and the fault code is displayed to display "the intake pressure sensor is bad".
Unplug the intake pressure sensor plug and measure the supply voltage to 5V. The signal voltage fluctuates from 2.8 to 2.9V, and under normal conditions should be about 1.3 to 1.5V. Obviously, the voltage is too high, causing the engine control unit to supply oil. excessive. Since the output voltage of the intake pressure sensor is directly related to the degree of vacuum of the engine, it is decided to measure the degree of vacuum.
The digital vacuum gauge was connected to a vacuum tube and it was found that the degree of vacuum fluctuated around 20 kPa, which is far from the normal value of 50-60 kPa. At this point, first check the vacuum for leaks, and clamp each rubber tube on the intake pipe one by one. When the other rubber tube leading to the check valve on the intake pressure sensor is clamped, the digital vacuum gauge value is displayed. Immediately rise to 50kPa, the engine works stably, no longer black smoke. Looking down the pipe, it was found that it was passed through a thin iron pipe to the oil pressure regulator, but the middle had been disengaged, and after it was inserted, the fault was completely eliminated.
2. The engine is not accelerating. A 2000-year-old Fukang 1.6L sedan has an unstable engine speed and a bit of black smoke. It needs to continuously shake the throttle to start at the start. When the speed reaches 40km/h, the acceleration performance improves. After taking the car and testing the car, I found that the brake pedal was hard when I stepped on the brake. Repeated testing, it feels like the vacuum booster does not work, it is suspected that the acceleration weakness is directly related to the brake failure. A thorough visual inspection was performed, and there was no vacuum tube drop and vacuum leak. Remove the spark plug to measure the cylinder pressure is normal. After connecting the digital display vacuum gauge to the throttle valve, the engine is started to idle speed, and the vacuum gauge value is displayed back and forth between 37 and 50 kPa. It seems that it may be caused by the valve closing is not strict. The cylinder head was dismantled and it was found that the intake valves of the two cylinders and the exhaust valves of one cylinder had different degrees of air leakage. After replacing a set of valves, the fault is completely eliminated.
This car should be stable at 61 kPa when it is idling normally. This value is far below the standard value. Most people will have two questions: First, why the valve leaks and the cylinder pressure is normal. This is because the engine runs continuously during the measurement. When the gas volume is not very large, the cylinder pressure will not decrease too much; the second is why the low speed is weak and the medium speed is above normal. This is because at the start, the engine cylinders have less inflation, and at this time, due to the increased engine load, the valve The movement speed is low, resulting in a large amount of air leakage. At high speeds, because the valve speed is increased, the amount of air leakage is relatively reduced, and the power drop is not large, so there is no obvious abnormality when driving at high speed.
As a simple and effective detection tool, the digital vacuum gauge can bring a lot of convenience to the maintenance work in the fault diagnosis as long as it is used properly. In many cases, the maintenance efficiency can be greatly improved.
3. Packing:
a) Inner packing: each piece is wrapped with tissue paper and foam net
b) Outer packing:
1) 4.5kg/carton: 20, 22, 24pcs 2) 9kg/carton: 40, 44pcs
3) 10kg/carton: 36, 40,44,48pcs 4) 18kg/carton: 72, 80, 96pcs
5) or according to clients' requirements.
4. Supply period: End August to next April
First, the advantages of the digital vacuum table 1, the measurement results accurate digital display vacuum table to display the measurement results, at a glance, no artificial reading error.
2, the measurement range of large digital vacuum gauges generally larger than the pointer vacuum gauge measurement range, usually 2 to 3 times the pointer type multimeter.
3, the overload capacity of the digital display vacuum table generally has a relatively complete protection circuit, generally does not damage the integrated circuit in the table.
4, the function is extended, the digital display vacuum table has a large-scale integrated circuit inside, and the digital display technology is adopted. Therefore, some new functions are expanded in the original test function, especially the online function of the computer, which will make the digital vacuum watch The intelligence aspect has been greatly enhanced.
Second, the digital vacuum gauge test method 1, before the test preparation In order to better use the digital vacuum gauge to diagnose the fault, the test must ensure that the ignition timing and idle limit values ​​are in the normal range, under this premise, any deviation The value of the normal vacuum indicates that the engine is faulty.
2. When determining the engine fault measurement according to different engine speeds, the vacuum of the vacuum gauge must be directly derived from the intake manifold, because only the vacuum of the intake manifold is directly derived from the vacuum of the engine. In order to distinguish the faults reflected by the vacuum values ​​under different working conditions, the vacuum degree of the engine intake manifold can be divided into three basic types: idle speed test, rapid acceleration test and exhaust system block test.
(1) Idle speed test When the engine is working normally, the value should be 50~70kPa measured by vacuum gauge under idle condition. If the measured value is not in this range, it should be analyzed according to different situations to determine the fault.
1 If the vacuum gauge value during the idle test is low and stable, the following checks should be made: check the initial ignition timing; check the valve timing; check the cylinder pressure; check the crankcase forced air control valve.
2 If the vacuum gauge value during the idle test is regularly decreased by 6~9kPa, the following checks should be made: check if there is a spark plug that is not working; check if there is a burnt valve (cylinder pressure test); check if there is burnout Piston (cylinder pressure test).
3 If the vacuum gauge value is found to fall irregularly to 10~27kPa, the following checks should be made: check the spark plug; find the stuck valve; look for the stuck valve lifter or hydraulic tappet.
4 If the vacuum gauge value is displayed slowly at 27~34kPa, the following work should be performed: check if the mixture is too rich; check if the spark plug gap is too small.
5 If the vacuum gauge pointer is displayed at 47~61kPa quickly when idling, the intake valve tappet and the pipe are worn and loose. If the vacuum gauge pointer is displayed slowly between 34 and 76 kPa, and the value jumps as the engine speed increases, the valve spring elasticity is insufficient.
6 If the value of the vacuum gauge is displayed back and forth between 18 and 65 kPa at idle, it is caused by air leakage from the cylinder liner.
7 If the engine idle speed is too high, the test manifold vacuum is less than 40 kPa, indicating that the manifold or the main pipe leaks after the throttle of the engine, and the leakage portion is generally a manifold pad and a plurality of pipes connected to the manifold. Such as vacuum booster air pipe and so on. When I was repairing a Mercedes 560SEL sedan, I used this method to detect the air leakage. I also used the elimination method to determine the fault location in the steering assist control valve. After the Zui, it was determined that the power supply fuse was controlled by the steering assist control valve. Troubleshoot after replacing the fuse.
8 If the engine is difficult to start, the stable idle speed cannot be guaranteed, and the vacuum of the test engine is above 50 kPa. It indicates that there is no problem in the intake pipe of the engine. The fault lies in poor ignition or poor fuel injection caused by the electronic control system, such as ignition coil failure.
(2) The rapid acceleration test is performed when the engine is rapidly accelerating, and the degree of leakage of the piston can also be displayed. When accelerating, the reading of the vacuum gauge should suddenly drop; when the speed is decelerated, the vacuum gauge value will jump up sharply at the original idle speed. That is, when the throttle is quickly opened and closed, the value of the vacuum gauge should fluctuate between 7 and 8 kPa.
1 If the piston leaks seriously, the swing amplitude of the vacuum gauge pointer will be less obvious. The wider the swing of the vacuum gauge pointer, the better the engine's technical condition.
2 If the value of the vacuum gauge is lower than the normal value when idling, the pointer will fall back to “0†when the acceleration is rapid, and the pointer cannot be raised to about 86 kPa when the throttle is suddenly closed. This phenomenon is mainly caused by air leakage from the piston ring and the intake pipe gasket.
(3) Exhaust system blocking test This test is carried out under the condition of engine speed of 1000r/min. Careful observation of the vacuum gauge reading, if the reading is gradually decreased gradually, indicates that the exhaust system is blocked.
It should be noted that the above values ​​are all measured at the height equivalent to sea level. We know that the intake manifold vacuum decreases with increasing altitude. Generally, for every 500m increase in altitude, the vacuum will be reduced by 5.5kPa. Therefore, when measuring the intake manifold vacuum, we should convert according to the altitude.
Third, the use of vacuum gauge to diagnose engine faults, combined with the diagnosis of fault cases to analyze the application of vacuum gauges in fault diagnosis.
1. When the idling speed is exhausted, the exhaust pipe emits black smoke. In 1996, the Krona sedan was produced. When the idling speed, the exhaust pipe emits black smoke, and the fuel consumption is large. When the acceleration is accelerated, the black smoke is larger and the idle speed is unstable. According to the fault phenomenon, it is basically judged that the mixed gas is too rich, and the fault code is displayed to display "the intake pressure sensor is bad".
Unplug the intake pressure sensor plug and measure the supply voltage to 5V. The signal voltage fluctuates from 2.8 to 2.9V, and under normal conditions should be about 1.3 to 1.5V. Obviously, the voltage is too high, causing the engine control unit to supply oil. excessive. Since the output voltage of the intake pressure sensor is directly related to the degree of vacuum of the engine, it is decided to measure the degree of vacuum.
The digital vacuum gauge was connected to a vacuum tube and it was found that the degree of vacuum fluctuated around 20 kPa, which is far from the normal value of 50-60 kPa. At this point, first check the vacuum for leaks, and clamp each rubber tube on the intake pipe one by one. When the other rubber tube leading to the check valve on the intake pressure sensor is clamped, the digital vacuum gauge value is displayed. Immediately rise to 50kPa, the engine works stably, no longer black smoke. Looking down the pipe, it was found that it was passed through a thin iron pipe to the oil pressure regulator, but the middle had been disengaged, and after it was inserted, the fault was completely eliminated.
2. The engine is not accelerating. A 2000-year-old Fukang 1.6L sedan has an unstable engine speed and a bit of black smoke. It needs to continuously shake the throttle to start at the start. When the speed reaches 40km/h, the acceleration performance improves. After taking the car and testing the car, I found that the brake pedal was hard when I stepped on the brake. Repeated testing, it feels like the vacuum booster does not work, it is suspected that the acceleration weakness is directly related to the brake failure. A thorough visual inspection was performed, and there was no vacuum tube drop and vacuum leak. Remove the spark plug to measure the cylinder pressure is normal. After connecting the digital display vacuum gauge to the throttle valve, the engine is started to idle speed, and the vacuum gauge value is displayed back and forth between 37 and 50 kPa. It seems that it may be caused by the valve closing is not strict. The cylinder head was dismantled and it was found that the intake valves of the two cylinders and the exhaust valves of one cylinder had different degrees of air leakage. After replacing a set of valves, the fault is completely eliminated.
This car should be stable at 61 kPa when it is idling normally. This value is far below the standard value. Most people will have two questions: First, why the valve leaks and the cylinder pressure is normal. This is because the engine runs continuously during the measurement. When the gas volume is not very large, the cylinder pressure will not decrease too much; the second is why the low speed is weak and the medium speed is above normal. This is because at the start, the engine cylinders have less inflation, and at this time, due to the increased engine load, the valve The movement speed is low, resulting in a large amount of air leakage. At high speeds, because the valve speed is increased, the amount of air leakage is relatively reduced, and the power drop is not large, so there is no obvious abnormality when driving at high speed.
As a simple and effective detection tool, the digital vacuum gauge can bring a lot of convenience to the maintenance work in the fault diagnosis as long as it is used properly. In many cases, the maintenance efficiency can be greatly improved.
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a) Inner packing: each piece is wrapped with tissue paper and foam net
b) Outer packing:
1) 4.5kg/carton: 20, 22, 24pcs 2) 9kg/carton: 40, 44pcs
3) 10kg/carton: 36, 40,44,48pcs 4) 18kg/carton: 72, 80, 96pcs
5) or according to clients' requirements.
4. Supply period: End August to next April
5. Conveyance: Loading quantity for each 40`HR depending on its detailed packing.
6. Transporting and storing temperature: 0°C
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