I. Summary

This paper introduces that the contact of ignition circuit breaker of Toyota Sea Lion IRZ car is often ablated, which leads to the firing of engine exhaust muffler, serious exhaust gas emission and power reduction. By repairing the circuit breaker and replacing the capacitor, the phenomenon of frequent ablation of the vehicle circuit breaker is overcome and the resulting faults are eliminated.

Keywords: full and complete combustion; Poor contact; Electric spark is not strong; Ignition timing

Second, the preface

With the rapid development of China's national economy, the number of cars is increasing, and the requirements for the use of cars in big cities are getting higher and higher, not only for the technical performance (such as power and economy) of cars, but also for the exhaust emission and noise of cars. Therefore, in the process of automobile maintenance, we can't ignore the influence of faults in all aspects.

Third, the text.

(1) When the engine is running, it will make a rhythmic "chug" sound.

My unit has a Toyota Sea Lion IRZ car (using the traditional battery ignition system). Driving about 80 thousand kilometers, when the engine is running, the exhaust muffler makes a rhythmic "chug" sound, and the higher the speed, the louder the sound, accompanied by carburetor tempering; The shooting phenomenon of exhaust muffler causes serious vehicle exhaust pollution, the engine power drops obviously, the engine shuts down frequently, and the economy deteriorates obviously.

(2) Cause analysis of engine failure.

In order to make the engine produce the highest power and less pollution, it is necessary to ensure that the engine can burn fully. The main condition for full combustion of the engine is that the ignition timing of the ignition system can generate enough sparks to burn the mixture. Because only ignition timing and full combustion can ensure that the engine can generate enough explosive force when doing work, drive the engine crankshaft to run at high speed, and at the same time, fully and completely burn, so as to ensure the maximum reduction of harmful exhaust gas and environmental pollution. Therefore, it is concluded that the failure of engine ignition system will make the ignition timing incorrect, and the generated electric spark will be weakened, thus reducing the sufficiency of combustion. If the fuel can't burn completely in the cylinder, the unburned exhaust gas will burn or be discharged in the exhaust throat, which will lead to the explosion of the exhaust throat or serious exhaust gas emission, and finally reduce the output power of the engine.

According to the above analysis, I unplugged the high-voltage line of a cylinder, and conducted a fire jump test, and found that the spark color was red, which proved this point.

The spark is too weak. This is the reason for the failure of insufficient combustion. The reasons for the weak ignition spark of the engine ignition system are as follows:

1. The contact resistance of the high-voltage line is too large.

The high voltage generated by the ignition coil is distributed to the center electrode of the spark plug through the high voltage line. Because the high-voltage electricity is transformed by the ignition coil, and the side electrode of the spark plug is connected to the ground, the high-voltage electricity can jump over the gap until the side electrode of the spark plug is grounded, and a fire arc is generated at the moment when the voltage jumps over the gap. If the contact resistance of the high-voltage line becomes larger, the voltage will decrease, and the generated spark energy will inevitably decrease, which will weaken the spark energy and make the spark weaker.

2. Short-circuit leakage fault of distributor cover

The distributor cover distributes high-voltage electricity from the central high-voltage line to the secondary high-voltage line of each cylinder. If its leakage or the ablation of the central carbon essence with each high-voltage conductive column causes poor contact, it will also reduce the energy of high-voltage electricity, thus reducing the energy of electric spark and weakening it.

3. Poor contact failure caused by flame distributor combustion.

The distributor is used to transmit high-voltage electricity from the carbon rod in the center of the distributor cover to each conductive column of the distributor cover. High voltage electricity is conducted by the conductive sheet of the distributor. When the conductive sheet is ablated and burned, it will lead to poor high voltage conduction, resulting in voltage drop and high voltage energy drop, thus reducing the spark energy and weakening the spark.

4. The contact of circuit breaker is dirty and ablated, resulting in poor contact failure.

The contact resistance of the circuit breaker is too large due to dirt or ablation. The circuit breaker contact is used to control the periodic on-off of the primary circuit of the ignition coil. If the contact resistance increases, the primary current of the ignition system will decrease, and the final coupled high voltage will also decrease. When the high-voltage electricity is reduced, the generated electric sparks are also reduced.

5. Capacitor open circuit fault

Capacitors are used to connect the contacts of circuit breakers in parallel to absorb the sparks generated when the contacts are disconnected. If the capacitor is short-circuited, the contact of the circuit breaker cannot be opened to cut off the primary current, so there is no high voltage and the ignition system does not work. If the capacitor is broken, the contacts of the circuit breaker will be ablated, resulting in poor contact, thus reducing the energy of the electric spark and weakening it.

6. The automatic adjustment mechanism of the ignition system advance angle is faulty.

When the engine piston goes up to this point, the compression ratio of the combustible mixture is the largest, the pressure generated at this time is the largest, and the power generated during explosion is also the largest. When the engine is running at high speed, the piston moves in the cylinder, and each stroke only needs about 0. Ols, and the combustible mixture takes about 0.003s from spark ignition to explosion. According to the theoretical design, when the piston goes up to the compression top dead center, the ignition system begins to generate electric sparks, and the mixed explosion is ignited by the electric sparks, so the piston has moved down by about 1/3, and the pressure at this time is relatively reduced, so the generated explosive force will be weakened. In order to make the engine piston explode just at the top dead center, the ignition system must start to generate electric spark when the piston is about 0.003s away from the top dead center, which is called engine ignition advance. The ignition of the engine is advanced by the crankshaft control distributor assembly. When the piston has not reached the top dead center, the corresponding crank angle is the ignition advance angle. That is to say, when the piston reaches the top dead center of the compression stroke, it is equivalent to that the crankshaft has turned a certain angle. When the ignition is advanced to a certain angle of top dead center, the gas pressure can reach the maximum. Therefore, before the piston reaches the top dead center of the compression stroke, the ignition time should have a certain angle with respect to the crankshaft. However, if the ignition advance angle is too large and the mixture is ignited prematurely, the gas pressure will hinder the upward movement of the piston, which will reduce the engine power, increase the fuel consumption, make the engine unstable and idle poorly, and will cause explosion and flammability under heavy load conditions. If the ignition advance angle is too small, the mixture will ignite too late, that is, the mixture will not be ignited when the piston reaches the top dead center, and the mixture will be ignited after the piston moves down from the top dead center. Due to the reduction of compression force, the explosive force will be reduced, which will lead to the unburned mixture burning outside the engine exhaust pipe and reduce the power. Therefore, improper or ineffective adjustment of the ignition advance angle of the ignition system will also lead to the shooting of the engine exhaust throat and serious exhaust emissions.

(3) Measures and methods for troubleshooting

According to the analysis of the above reasons, I have repeatedly studied the relevant maintenance materials around the failure phenomenon of the engine when it is not completely burned, humbly asked experienced masters to check and analyze the possible reasons one by one, and adopted the method of easy first and then difficult to check the parts that may cause the failure. The inspection methods and steps are as follows:

1. High voltage wire inspection

No corrosion, fracture or deformation was found by observing the high-voltage wires and terminals. The resistance of each wire (when the cover is not removed) is normal, and the measured resistance values are listed in the table.

2. Check the distributor cover

First, check the carbon contact in the center of the distributor cover, the conductive piles distributed in the cover and the high-voltage ignition wire sockets on the cover, and no ablation and blackening are found. Unplug all the high-voltage wires on the spark plug, remove the distributor cover (as shown in the figure), keep the ends of all the high-voltage wires 3 ~ 4 mm away from the cylinder, turn on the ignition switch, and toggle the contact arm of the disconnector so that there is no fire between the distributor head and the cylinder block. Unplug all high-voltage lines on the distributor cover, insert the central high-voltage line into any high-voltage line jack, and insert another high-voltage branch line into the jack adjacent to its branch hole, so that its end is 3 ~ 4 mm away from the cylinder block. Turn on the ignition switch and toggle the contact arm of the disconnector. There is no flashover between the branch terminal and the cylinder block. Then use this method to check other high-voltage branch jacks, and there is no leakage, which proves that the distributor cover has no leakage fault.

3. Fire detection

First, observe the end of the conductive sheet of the distributor, and no burning or scorching phenomenon is found. Then, put the distributor on the cylinder head (as shown in the figure), so that its conductive sheet contacts with the cylinder. Then, put one end of the high-voltage line about 2 ~ 3 mm away from the distributor seat hole, turn on the ignition switch at the same time, and toggle the contact arm of the circuit breaker to make it open and close. At this time, there is no spark jumping between the holes of the ignition head seat at the end of the high-voltage line, indicating that the ignition head works normally.

4. Check the ignition adjusting device

When the distributor assembly is disassembled, it is found that the centrifugal counterweight of the centrifugal regulator swings flexibly and smoothly, without jamming and looseness. The distributor shaft is fixed, so the cam rotates to the limit position in the normal rotation direction. Suddenly released, the cam immediately returned to its original position, which proved that the centrifugal regulator worked normally. Check the vacuum regulator, the diaphragm is free of cracks, the pull rod is firmly connected with the spring, and the nut of the pipe joint is free of leakage, indicating that the vacuum regulator is good.

5. Check the circuit breaker

When the contact is closed, hook the tip of the moving contact with the hook of the spring scale (as shown in the figure) and pull the spring along the axial direction of the contact. The tension reading is 57.8N(5.9kgf), indicating that the tension of the contact arm is normal. Then move the contact arm of the circuit breaker to observe its contact, and find that the contact has serious ablation. Using multimeter to measure the resistance between contacts, the indicator number is 5 Ω, which proves that the increase of contact resistance reduces the primary current and high voltage, which leads to the reduction of EDM failure.

6. Capacitor inspection

Remove the capacitor and put it on the cylinder head (as shown in the figure), so that the high voltage bus end on the ignition coil is 3 ~ 5 mm away from the capacitor lead. Turn on the ignition switch, toggle the contacts of the circuit breaker, so that it can be divided and contracted for 3 ~ 4 times. At this time, there is a spark between the end of the high voltage bus and the lead of the capacitor. Immediately scrape off the capacitor lead and its shell (i.e. discharge), which can't produce strong blue-white sparks, and judge the damage.

Through the above comprehensive detection and judgment, it is found that the engine emits rhythmic "sudden" sound at various speeds, and the main cause of engine flameout failure is the damage of capacitor, which leads to frequent ablation of circuit breaker contacts. When the ignition system works and the contacts of the circuit breaker are opened, the magnetic field changes with the decrease of the primary current. When the secondary winding generates high voltage, it also generates self-induced electromotive force in the primary winding, which can reach 200 ~ 300 V. It will act on the contact gap, break through the contact gap, generate sparks, and make the contact quickly ablate. At the same time, the primary current cannot be interrupted quickly, and the magnetic field changes slowly, thus reducing the secondary voltage. In order to eliminate this influence, a capacitor is connected in parallel at both ends of the contact. When the contact is disconnected, the self-induced electromotive force generated by the primary winding charges the capacitor. Due to the appropriate capacitance, the charging time is extremely short, which not only reduces the spark between contacts and prolongs the service life of contacts, but also accelerates the disappearance of primary current and improves the rate of change of magnetic field, thus improving the secondary voltage. Therefore, the contact ablation and capacitor damage of circuit breaker lead to the decrease of low voltage current, secondary voltage and spark energy, which leads to the failure of ignition system.

After the above analysis and judgment of the fault, I decided to replace the capacitor and repair the contact of the circuit breaker. The contact was seriously ablated. The contact was repaired by removing the circuit breaker, and a small amount of oil was added to the fine oilstone to make it smooth, and the limit requirement of contact thickness < < 0.5mm was found. Replace the new circuit breaker, adjust the contact gap to 0.35 ~ 0.45 mm after reassembly, and put it back into the distributor assembly for trial operation. At various engine speeds, the muffler didn't make a "chug" sound and didn't shut down, and everything was normal.

(4) Conclusion

Through the above methods and steps, the problems of engine exhaust shooting and power reduction of this car in our unit were finally repaired. It is concluded that the fault is caused by the capacitor fault of the ignition system, which leads to the contact being ablated by the spark when the contact is disconnected, which increases the contact resistance of the contact, resulting in low high voltage, weak spark and incomplete combustion of the mixture in the cylinder. Therefore, as a driver, he should not only abide by traffic laws and regulations to ensure driving safety, but also be familiar with and master the technical conditions of the vehicles he drives, understand the causes and solutions of the fault characteristics of ordinary cars, and ensure the good condition of the vehicles through daily maintenance.