The car ignition system offers the spark plug sufficient energy of high voltage (about 15000-30000V) at regular intervals according to the ignition sequence of each cylinder. As a result, the spark plug produces enough sparks to ignite the combustible air-fuel mixture. In this article, let's talk about the common problems of the car ignition system.
1. Tips for ignition system repair
2. Failure analysis and troubleshooting
2.1 Inaccurate ignition timing
1. Tips for ignition system repair
● When the engine starts to work, keep your hands away from the high-voltage wire of the ignition coil to avoid electric shock.
● When checking circuit failure of the ignition system, set the multimeter to the "resistance" range to check the on-off of the circuit. Take care to prevent damage to electronic components.
● While doing the high-voltage test, it is best to use insulated rubber clamps to hold the high-voltage line. It is easy to cause an electric shock by directly touching the high-voltage line with your hands.
Another way to avoid electric shock is to plug the high-voltage wire into a spare spark plug. Then latch the spark plug housing and observe whether the spark plug electrodes generate sparks. Be careful to avoid damage to the ignition module due to overvoltage.
● In the case of turning on the ignition switch, don't do the operation of connecting or cutting wires. Otherwise, the electronic components in the controller will be broken down.
● While removing the battery, you must make sure that the ignition switch and all other electrical devices are turned off before disassembly.
● When installing the battery, be sure to identify the positive and negative poles. The wrong connection is unacceptable. Battery poles and the connection of the wire clamps must be solid. Otherwise, it is easy to damage electronic equipment.
● The measurement action should be fast when checking the electronic ignition controller with a battery to simulate the ignition signal. The duration of the battery connection should not exceed 5s in general.
● Hall effect electronic ignition system may produce high-voltage discharge during inspection and maintenance. This may cause accidental damage to people and the ignition system itself. Therefore, the following points must be noted.
① Power should be cut off before carrrying out any inspection and maintenance.
② When using an external power supply for maintenance, the voltage should be strictly limited not greater than 16V. When the voltage reaches 16 ~ 16.5V, the connection duration is not allowed to reach or exceed 1 min.
③ If a car with Hall-effect electronic ignition system is towed, the power should be cut off first.
④ The negative terminal of the ignition coil is not allowed to be connected to the capacitor.
⑤ Under any conditions, the ignition head is only allowed to be 1 kΩ. The component with this resistance value can prevent electromagnetic interference. It shall not be replaced by others. The resistance of the spark plug should be 1-5 kΩ.
2. Failure analysis and troubleshooting
2.1 Inaccurate ignition timing
Symptoms
① Hard starting problem
② Unstable idle speed
③ Insufficient engine power
④ High water temperature
⑤ Easy engine knocking
Reasons
Bad crankshaft position sensor or incorrect mounting position
Troubleshooting
The main components that mislead the engine ignition timing are the engine ignition reference sensor and crankshaft position sensor.
Check whether the signal rotor is deformed and skewed, whether the signal acquisition and output part are installed improperly, and whether the clearance of the device is appropriate.
Symptoms
Spark plugs are working under high temperatures and pressure. They are also subject to the corrosive effect of chemical additives in the fuel. The work conditions are harsh. Therefore, the failure rate is high. Common failures of spark plugs are as follows.
● Burnt spark plugs
Problems of wrinkled insulator, rupture, electrode ablation, melting and others will make the leakage of the spark plug or puncture voltage increase, resulting in the lack of sparks. The vehicle can not run smoothly.
● Deposits in components
Deposits formed by carbon, oil and ash accumulated on the spark plug will increase the spark plug's leakage and puncture voltage. These problems will cause the engine to lack sparks or fail to work.
● Too large or too small spark plug gap
These two issues drop the ignition performance and lead to no sparks.
Troubleshooting
The inspection of the spark plug is simple. Look at the appearance of the electrode and insulator. Check if there are any of the faults as mentioned earlier.
The normal insulator skirt of the spark plug is light brown or off-white. Few carbon accumulations and electrode ablation are normal.
Symptoms
Turn on the ignition switch, the engine judders at idling.
Reasons
① No voltage or too low voltage at the primary end of the coil
② The ignition coil is not fixed
③ Too high ignition resistance and broken circuit in the ignition cable
④ The negative overlap circuit in the primary winding is not controlled by the ignition module
⑤ Damaged crankshaft position sensor
⑥ Defective ignition module or ECU
Troubleshooting
① Observe the ignition system for any apparent abnormalities
② Read trouble codes with diagnostic equipment
③ Check if there are sparks
④ Test the power supply circuit of the ignition coil
⑤ Test the ignition coil
⑥ Test the crankshaft/camshaft position sensor
⑦ Test the ignition signal and ignition feedback signal
Symptoms
① Broken circuit in the primary winding and secondary winding
② Short circuit between turns
③ Windings latching
④ Aging insulator and leakage
⑤ Poor contact of internal wire connection points
These problems may lead to no secondary voltage, or the secondary voltage is too low to ignite. In other cases, the engine can generate sparks, but the secondary voltage is reduced. The ignition energy is insufficient.
The sparks will be broken at high speed. And the engine will not start easily. The idling speed is unstable. The power is reduced. The exhaust pollution is increased.
Inspection
To check the ignition coil, we usually set the multimeter to the "resistance" range to measure the primary and secondary windings respectively, to determine whether there is a short circuit or broken winding fault. If the value is infinite, the winding has a circuit fault.
If the resistance is too large or too small, the winding has poor contact or a short circuit. Check if the winding is lapped, then use a universal meter to measure the resistance between the ignition coil terminals and the ignition coil shell. If the value is zero, the winding overlaps.
Some faults of the ignition coil are not necessarily only tested by the method of measuring resistance with a multimeter. For example, the problem of aging internal insulation of the ignition coil or small cracks exists. These issues are just under high voltage leakage.
They cause the secondary voltage to drop and the ignition energy to be insufficient to make the engine work properly or even not work. These faults need special instruments to discern.
Symptoms
After starting the engine, step down the pedal little by little. We can hear the rhythmic sound in the exhaust muffler during the whole speed-boosting process from low speed to high speed. Meanwhile, the engine shakes during idling.
Reasons
① Damaged spark plugs
② Faulty ignition coils
③ Lack of fuel
④ Insufficient oil pressure
Troubleshooting
● Check the ignition system
If a cylinder does not work, unplug the high-pressure subline. It is 5-7 mm away from the spark plug. Observe whether there are sparks.
If there are no sparks, remove the spark plug from the engine and test whether the gap is normal and the electrode part is good. If there is a problem, replace it. If it is normal, check whether the ignition coil is faulty.
● Check the fuel system
If the fuel supply is insufficient, it will also cause the engine to shake. Connect the fuel pressure gauge in series in the fuel inlet pipe. Start the engine to check the fuel pressure. Check the idle oil pressure, acceleration change oil pressure and the pressure after stalling, respectively.
Symptoms
① Weak sparks during the test
② Hard starting
③ Unstable idle speed
④ Black smoke exhaust
⑤ Poor acceleration and bad medium and high speed
Reasons
① Faulty ignition controller and ignition coil
② Too large resistance of high voltage wire
③ Leakage or carbon deposits in the spark plug
④ Insufficient voltage in the ignition system
⑤ Poor grounding
Troubleshooting
Check whether the ignition controller and ignition coil are in good working condition, whether the power supply voltage is normal, whether the plug and wire connection is solid, and whether the ignition latch is reliable. Remove carbon deposits on the spark plug. Replace the leaky parts.
Symptoms
It works normally at low speed and stalls at high speed. It is normal when the temperature is low and abnormal when the temperature is high. It is normal when starting but bad after the vehicle runs for a while.
Reasons
① Loose installation of the ignition reference sensor and crankshaft angle and speed sensor
② Poor contact of circuit connection devices
③ Poor thermal stability of the ignition
④ Partial damage or breakdown of the ignition cable
⑤ Too large resistance of the high voltage wire
Troubleshooting
Check whether the relevant parts are installed loosely, whether the circuit connection is solid and reliable, whether the ignitor and ignition coil are abnormal. Check or replace the ignition cable and spark plug.
Lauritz Carolsfeld 
November 22, 2021