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Inspection and elimination of common faults of engine ignition system

Under normal circumstances, the engine suddenly turns off during operation, and the reason for the failure to start is mostly the failure of the ignition system. Ignition system failures are manifested as no fire, misfire, weak spark, and incorrect ignition.


(1) The engine cannot be started

Turn on the ignition switch and the engine cannot start. It may be caused by abnormal power supply, incorrect ignition timing or poor spark plug. The maintenance methods are as follows.

Honk the horn or turn on the headlight first. If the horn does not sound or the headlight is dark, it means that the power supply is abnormal. After confirming that the power supply is normal, judge whether the fault occurs in the high-voltage circuit or the low-voltage circuit. Open the engine hood, pull out the central high-voltage line of the distributor, make it 4~6mm away from the cylinder block, turn on the ignition switch, turn on the starter circuit for a short time, and check the spark.

① The spark is strong, indicating that the low-voltage circuit and the ignition coil are in good condition, and the fault lies in the distributor and the high-voltage circuit of the spark plug. Then remove the high-voltage wire from the upper end of the spark plug, shake the crankshaft or start the starter to test the body, if there is no spark, it may be the leakage of the spark plug, the distributor and the high-voltage wire. Check whether the spark plug, the distributor and the high-voltage wire are leaking; If there is a spark, the ignition timing and spark plug may be poor. Check the ignition timing and the working condition of the spark plug.

② Weak or no sparks indicate that the low-voltage circuit and short circuit, open circuit, failure of ignition electronic components or failure of ignition coil and central high-voltage line. The contacts can be opened and closed, and the reading of the current pointer can be observed. If the ammeter pointer does not swing, the indication is zero, indicating that the low-voltage circuit is open; if the ammeter pointer does not swing at 3~5A or indicates a large current, it indicates that there is a ground fault in the low-voltage circuit; if the ammeter pointer points intermittently between 3~5A Swing means that the low-voltage circuit is good, and the fault occurs in the high-voltage circuit.



(2) The engine can be started

The engine can start, but it does not work properly, and the exhaust pipe emits black smoke with jitter.

If one or several cylinders miss fire, the engine will run unevenly, and black smoke will be discharged from the exhaust pipe and the cannon will be fired. Most of the causes are leakage or fall off of high-voltage branch lines, leakage of distributor cover, uneven cam wear, poor or non-working spark plugs, and wrong insertion of high-voltage branch lines. During the inspection, find out the cylinder with misfire first, and then eliminate the cause of the misfire. The method is to start the engine, ground the spark plug nuts one by one with a screwdriver, and observe the operation of the engine. If there is no change in the engine speed after grounding, it means that the cylinder is not working; if the engine speed is significantly reduced after grounding, it means that the cylinder is working normally, and then further check according to the situation.

① If a cylinder is not working, remove the high-voltage branch line on the spark plug of the cylinder so that the wire end is 3~4mm away from the spark plug terminal. When the engine is working, if there is continuous spark in the gap and the engine runs evenly, It indicates that the spark plug is carbonized; if there is no spark, it indicates that the high-voltage branch line or the distributor cover is faulty and should be repaired or replaced.

② When the two cylinders are not working, check whether the ignition sequence is correct.

③ If several cylinders are not working at the same time, unplug the central high-voltage line of the distributor cover for a flashover test. If the flashover is normal, it means that the high-voltage power supply is normal, and the fault is on the distributor cover, high-voltage branch line or spark plug. Repair or replace; if the flashover occurs intermittently, it indicates that the breaker cam, capacitor or ignition coil is faulty. Clean the power-off gear first, and then check the capacitor and ignition coil.


(3) The engine cannot run at high speed

The engine works well at low and medium speeds, but runs unsteadily at high speeds, and the muffler emits a rhythmic "burst" sound. The reasons for the failure include: too large contact gap during power-off; too weak spring force of contact arm spring; too large gap between spark plugs; bad capacitor; leakage of ignition coil, etc.

Repair method: first check the contacts, contact springs and capacitors of the breaker; if there is a problem, repair or replace it. If the fault still cannot be eliminated after replacement, it may be the leakage of the ignition coil. The terminal bolts can be removed and cleaned, and the bolts can be pressed and installed with rubber pads to eliminate the leakage fault. 


4) Improper ignition time

Improper ignition timing performance: The battery is working with sufficient power, but the engine is not easy to start, driving is weak, acceleration is stuffy, the exhaust pipe is fired, and the engine is overheated. It should be checked whether the ignition is too late and the distributor is loose; when the crankshaft is cranked, it reverses and knocks when accelerating. It should be checked whether the ignition is too early. If the ignition time is too late, the ignition timing should be adjusted. If the ignition timing is normal, the contact gap may be too small, just adjust it appropriately. If the fault still cannot be eliminated, it may be that the distributor shell is loose, just tighten it.

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