The working condition of automobile ignition system directly affects the power and economy of the engine. In the process of automobile maintenance, the failure rate of ignition system is relatively high. Therefore, this paper introduces the common fault diagnosis of automobile ignition system and puts forward the maintenance methods.
A, the classification of automobile ignition system
Automobile ignition system is generally divided into distributor and distributor-free. Generally, the ignition coil controls the ignition of all cylinders in the distributor. There are two types of distributor-less ignition systems. One is that two cylinders are ignited at the same time with one ignition coil, one is effective and the other is ineffective; There is also a cylinder and an ignition coil, which can be ignited independently without high voltage line sequence.
The following are some common faults: the engine can't start, the engine runs unsteadily, the engine power drops, the fuel consumption increases, and the acceleration is poor.
Fault analysis and troubleshooting: (1) The engine cannot be started. Faulty parts: circuit between ignition switch and distributor, ammeter, ignition switch, circuit breaker, capacitor, sensor, ignition controller, distributor cover or distributor head, high voltage conductor, spark plug, distributor and cylinder pipeline. Causes of failure: short circuit, open circuit, poor contact, ammeter and ignition switch damage, ignition coil damage, additional resistance fracture, contact oxidation ablation, poor grounding of fixed contact, wire break, grounding, contact gap is too large or too small, damage, induction coil short circuit, open circuit, grounding, improper gap between rotor cam and iron core, Hall element damage, damage, leakage, leakage or open circuit. Troubleshooting methods: check, tighten, replace wires, replace, replace, clean or replace, repair and strengthen grounding, repair, adjust, replace, repair or replace, adjust, replace, replace, clean or replace spark plugs with appropriate thermal characteristics, adjust, replace, re-adjust ignition timing, and re-wire after adjustment. (2) Fault parts of unstable engine operation: ignition timing, spark plug and high voltage lead. Causes of failure: improper adjustment of ignition timing, failure of ignition advance angle adjusting device, looseness of distributor shaft, uneven wear of circuit breaker cam, insulation damage or carbon deposition of spark plugs in individual cylinders, damage and leakage of pipelines in individual cylinders. Troubleshooting: reset ignition timing, repair or replace distributor, replace distributor, replace spark plug, and replace. (3) The engine power decreases, the fuel consumption increases, and the acceleration is poor. Faulty parts: ignition timing, circuit breaker. Cause of failure: improper adjustment of ignition timing, failure of ignition advance angle adjusting device and excessive contact gap. Troubleshooting: reset the ignition timing, repair or replace the distributor, repair or replace it.
Fault diagnosis of traditional ignition system (contact type)
The traditional ignition system consists of power supply, ignition switch, additional resistor, additional resistor short-circuit switch, ignition coil, distributor (including circuit breaker, distributor and ignition advance angle adjusting device), high-voltage line and spark plug.
When the primary circuit of the ignition coil is cut off, a high ignition voltage is generated, which is sent to the spark plug through the distributor and the high voltage line to ignite the combustible mixture in the cylinder.
The common fault causes of traditional ignition system are: (1) poor contact of low-voltage circuit, open circuit, short circuit, poor grounding or poor grounding; (2) Contact ablation, oil pollution, too large or too small gap, open connection and weak contact elasticity; (3) The capacitor is damaged and the additional resistance is open; (4) The battery loses power and the ignition switch is in poor contact; 5] The ignition coil is damaged and the high-voltage line leaks; [6] The distributor cover is damaged and the distributor head is damaged; Once the spark plug has carbon deposit, oil stain, broken insulator or improper gap; Being uneven distributor cam wear; Levies distribution plate shaft bending or wear loose kuang; ⑽ distributor vacuum ignition advance device or centrifugal ignition advance device failure; ⑾ The ignition timing is not allowed, and the cylinder line is disordered. Faults (1)-(5) are usually called low-voltage circuit faults, (6)-(8) are called high-voltage circuit faults, and (9)-( 10) are called comprehensive faults.
Fault diagnosis of electronic ignition system (contactless)
Electronic ignition system consists of sensor, ignition controller, distributor and spark plug. The contact of the circuit breaker is cancelled, and the primary current of the ignition coil is controlled by the ignition controller. According to the different working principles of ignition signal sensors, there are many forms such as magnetic pulse type and Hall effect type.
Composition and fault diagnosis of pulse contactless electronic ignition device
The magnetic pulse contactless electronic ignition device consists of a magnetic pulse sensor, an ignition controller, an ignition coil, an ignition switch and a storage battery. When the engine is working, the magnetic pulse sensor generates an alternating ignition signal, and the ignition controller controls the on-off of the primary current of the ignition coil and the operation of the ignition system.
Common failure causes of magnetic pulse contactless electronic ignition device are:
(1) The magnetic pulse signal generator is damaged; (2) The ignition controller is damaged; (3) The ignition coil is damaged or has poor performance; (4) Poor line contact or open circuit or short circuit; 5] distributor cover is broken and distributor head is damaged; [6] Spark plug carbon deposit, oil pollution, broken insulator or improper gap; Once the distributor vacuum ignition advance device or centrifugal ignition advance device fails; Being inaccurate ignition timing, cylinder pipeline disorder.
Composition and fault diagnosis of Hall effect contactless electronic ignition device
The Hall effect contactless electronic ignition device consists of an ignition switch, a storage battery, an ignition coil, a high-voltage distributor, a spark plug, a distributor, a Hall signal generator and an ignition controller. The ignition signal is generated by Hall sensor, and the ignition controller amplifies and shapes the ignition signal to control the on-off of the primary current of the ignition coil and the operation of the ignition system. The failure phenomenon of Hall effect contactless electronic ignition device is very similar to that of magnetic pulse contactless electronic ignition device, but the difference is that the ignition signal is generated by Hall sensor.
Fault diagnosis of ignition timing deviation
The optimal ignition time varies with engine working conditions. In order to make the engine get the best ignition advance angle under various working conditions, the distributor is equipped with centrifugal ignition regulator and vacuum ignition regulator, and the initial ignition advance angle (ignition timing) needs to be checked and adjusted manually. Run the engine to room temperature, and suddenly accelerate when the vehicle speed is 25-30km/h (the test speed varies with the vehicle type). If you can hear a short and slight deflagration sound and disappear immediately, it means that the ignition timing is correct.
If there is no deflagration sound, the ignition is too late; If the deflagration sound is serious, the ignition is premature. If the ignition is too late or too early, it should be adjusted. Loosen the distributor fixing plate and rotate the distributor housing against the rotating direction of distributor head (increase the ignition advance angle) or rotate the distributor housing along the rotating direction of distributor head (decrease the ignition advance angle). Repeat the above process, and fix the distributor after the ignition advance angle is normal.
Check the ignition timing with the ignition timing lamp.
The empirical method has poor accuracy in diagnosing ignition timing, and can't measure accurate ignition advance angle. The ignition timing lamp can be used to measure the ignition advance angle at different speeds.
The ignition timing light is a strobe. When the delay potentiometer is zero, the flash is synchronized with the ignition time of the cylinder. By adjusting the delay potentiometer, the flash time can be delayed. When the flash time is aligned with the top dead center mark, the indicated value on the potentiometer is the ignition advance angle. The initial ignition advance angle of the engine can be obtained by measuring the ignition advance angle at idle speed. Measuring the ignition advance angle under different working conditions can also reflect the working conditions of centrifugal ignition regulator and vacuum ignition regulator. Comparing the measured value with the standard value can judge whether the ignition timing is accurate and provide technical data for the adjustment of ignition timing.
Troubleshooting steps for a few cylinders not working:
Fault diagnosis of a few cylinders not working
Back to the hot broken car trembling, "chug" sound rhythmic.
A slightly higher idle speed is more obvious, and the cylinder failure is not too late.
When the car is running, if the engine is at various speeds, the muffler emits rhythmic sonic boom, which is mixed with carburetor backfire, muffler shooting, body trembling and other phenomena, so it should be stopped for inspection and troubleshooting. When judging this fault, listen at a speed slightly higher than the idle speed. At this time, sonic boom with rhythmic muffler is even more obvious. In addition, it can also be judged by the method of fast speed increase with small throttle.
Troubleshooting steps for cylinder not working:
Step 1, external inspection: check whether the high-voltage branch line falls off, leaks electricity or is inserted incorrectly without turning off the engine. If it falls off or is inserted incorrectly, it should be reinserted. Leakage, replace the high voltage branch line. If it is normal, it is necessary to disconnect each high-voltage branch line on the distributor cover and observe the working condition of the engine.
Step 2: flameout test: after disconnecting the high-pressure branch pipeline of a cylinder, if the engine speed drops, the cylinder works normally. If the engine speed increases, there are two jacks next to the cylinder on the distributor cover for series connection. If the engine speed is constant, the cylinder will not work. At this time, check the high-pressure branch spark of the cylinder.
Step 3, hanging fire test: there is no fire in the high voltage branch, which is the leakage of the socket next to the distributor cover or uneven wear of the cam angle. The spark in the high voltage branch is on fire, and observe the working condition of the engine.
Step 4, look at the speed: the engine speed has increased and the spark plug is not working well. If the engine speed remains unchanged, check the high voltage branch flashover at the spark plug end.
Step 5, flashover test: there is flashover, but the spark plug does not work. There is no fire, but the high voltage branch line is damaged.
Step 6, check the technical condition of the valve train: it may be that the valve spring is broken or too soft, or the cylinder pad is damaged, the valve seat is loose or the valve is improperly closed.
Fault diagnosis of weak high voltage spark
The sound of "chug" has no rhythm, and it is low, medium and high speed.
Tempering blasting emits black smoke, which is easy to extinguish and difficult to start.
The distance of fire jumping is five to seven, with bright colors and crisp sound.
Look at the standard when the thickness is normal, but don't make a mistake when the central fire jumps.
At various engine speeds, the muffler emits rhythmic "chug" sound and emits black smoke, which is more obvious at high speed than at low speed. This "chug" sound is aggravated when the engine accelerates rapidly, accompanied by the sound of muffler shooting, and sometimes the carburetor backfires, which is easy to cause the engine to stall. This is the fault feature of weak high voltage spark. In addition, when judging this kind of fault, we can also observe the flashover of high voltage branch line. For further examination. That is, remove the high-voltage branch line from the distributor cover and check the flashover phenomenon. If the spark jump distance is short, the sound is small, the spark is thin, the color is red, and sometimes the fire is broken, which belongs to the weak fault of high voltage spark.
In addition, if the distributor has slight leakage, there will be a phenomenon that the spark is strong when checking the central high-voltage line and weak when checking the branch line. When diagnosing faults, it is necessary to distinguish between central high-voltage line faults and branch line faults.