A modern car is a complex mechanism where every detail plays a role, but it is the ignition system that is responsible for starting the engine and its stable operation. When the engine begins to move, twitch or refuses to start, experienced drivers first of all sin on candles, forgetting that the source of the spark is the ignition. It is this unit that converts the low onboard voltage into a powerful impulse capable of breaking through the spark gap of the candle.
The problem is that the symptoms of a fault are often disguised as other breakdowns, causing owners to spend money to replace the serviceable parts. To avoid unnecessary costs and downtime of the machine, you need to know how to check the ignition coil or not it is working, using available tools. In this article, we will discuss all diagnostic methods, from visual inspection to accurate multimeter measurements.
Do not ignore the first signs of unstable engine operation, as ignition failures can lead to failure of the catalytic converter, the replacement of which is very expensive. Proper and timely diagnosis allows you to identify the problem at an early stage. We will look at how to distinguish the dying coil from other problems and what parameters need to be measured for an accurate verdict.
Typical symptoms of coil failure
Understanding how a car behaves when a faulty ignition system is the first step to a successful repair. Symptoms can manifest themselves differently depending on the type of system: individual (one coil per candle) or modular (one coil per two cylinders). Most often, the driver notices that the engine begins to work unevenly, especially at idle speeds.
One of the most obvious signs is trim-enginewhen one or more cylinders cease to ignite the fuel-air mixture. This is accompanied by vibration of the body, loss of power and characteristic change in the sound of the exhaust. The car can twitch when accelerating, and fuel consumption increases sharply, as unburned gasoline is thrown into the exhaust system.
β οΈ Warning: Operating a vehicle with a faulty coil may damage the electronic control unit (ECU) due to reverse currents and overload.
It is also worth paying attention to the behavior of the car under load. If there are dips or jerks when you sharply press the gas pedal, this is a sure sign of a weak spark. In modern machines on the dashboard will light up the indicator Check Engineand the diagnosis will show errors associated with ignition failures in specific cylinders.
Visual inspection and search for external defects
Before taking up measuring instruments, a thorough visual inspection is necessary. Often the cause of malfunction lies in obvious things that can be seen with the naked eye. The first thing you need to remove the decorative plastic lining of the engine and access the coil module or individual coils.
Carefully inspect the body of the part for cracks, chips or traces of melting. High voltage passing through the insulation can make its way out, leaving characteristic black paths or short-circuit on the surface. If you see such traces, further multimeter check may no longer be necessary - the part definitely needs to be replaced.
Pay special attention to the contact group and the high-voltage tip. The presence of oxides, white plaque or traces of moisture inside indicates a violation of tightness. Water and oil are conductors and can cause a current leak, which will cause the spark to be weak or disappear altogether. Also check the integrity of the wires going to the connector.
- π Look for black stripes or points on the coil body indicating a breakdown in the insulation.
- π§ Check for oil or antifreeze in the candle well that may have damaged the winding.
- π Examine the connectors for oxidation of contacts and reliability of fixation.
If no visual defects are found, this does not guarantee the serviceability of the unit, since the break or interturn closure of the winding externally may not be noticeable. However, a clean and dry module gives a better chance that the problem lies deeper in the electrical part. After an external examination, you can move to more accurate diagnostic methods.
Diagnosis by multimeter: testing resistance
The most affordable and common way to check is to measure the resistance of the windings using a multimeter. To carry out this procedure, the device must be switched to the resistance measurement mode (Ohms), selecting a limit of 200 Ohms for the primary and 20 kOhms for the secondary. Before you start measuring, make sure the engine is cooled, as the temperature affects the readings.
The primary winding is first checked. Multimeter chips are connected to the pins 1 and 2 (or the terminal contacts of the connector, depending on the design). Normal resistance here is usually in the range of 0.5 to 2.0 ohms. If the device shows zero, then there was a short circuit, and if one (infinity) β there was a break in the chain.
Then the secondary winding is measured. One probe is connected to the central high-voltage exit, and the second to one of the side contacts. Here the values will be much higher, usually from 6 to 15 kΞ©, although some manufacturers, for example, Bosch or Denso, ranges may differ. It is important to check the technical data for a particular car model.
Why can the readings float?
When measuring resistance, the numerical values may fluctuate slightly. This is normal if the spread does not exceed 10-15%. If the jumps are significant, perhaps there is an unstable contact or interturn circuit inside, which manifests itself only when heated.
Compare the data obtained with the reference values in the table below. Remember that even a slight deviation from the norm may indicate the beginning of the destruction of the insulation of the winding.
| Type of winding | Normal resistance | Sign of malfunction |
|---|---|---|
| Primary | 0.5 - 2.0 Ohm | 0 Ohm (KZ) or β (Break) |
| Secondary | 6.0 - 15.0 kom | Highly above or below the norm |
| Isolation. | Infinity (β) | Any meaning of resistance |
Oscilloscope and spark test
A more advanced method is to check the shape of the signal using a motor tester or oscilloscope. This method allows you to see not just the presence of a spark, but also its quality, duration and energy. The screen of the device displays a graph, according to which an experienced diagnostician can determine the condition of not only the coil, but also candles and nozzles.
If there is no specialized equipment, you can use the old-fashioned method of checking "for a spark". To do this, a candle is twisted, connected to the coil, and the entire structure is applied by a metal part to the mass of the engine. When scrolling the starter should skip a bright blue spark. A red or yellow spark indicates a weak charge.
β οΈ Warning: When checking for a spark on weight, never hold a candle or coil in your hands without insulation - an electric shock can be very strong and dangerous to health.
There is also a replacement method that is often used in maintenance stations. The doubtful coil is changed places with a knowingly serviceable one from the next cylinder. If after reshuffling the error in the diagnostic scanner "move" along with the coil to another cylinder, then the problem is in it.
Use dielectric lubrication when installing a new coil. It prevents the contact oxidation and facilitates the removal of the part in the future, protecting the rubber tip from drying out.
Table of malfunctions and causes of their occurrence
Understanding the causes of failure will help prevent a repeat of the situation in the future. The ignition coil is a reliable knot, but it has its enemies. Most often, problems arise due to overheating, vibration or moisture. Knowing these factors, you can extend the life of the ignition system.
Below is a table that will help to systematize possible problems and their sources. This will allow you to find the root of evil faster if simply replacing the coil does not help.
| Symptoms. | Possible cause | Decision |
|---|---|---|
| No spark. | Primary chain break | Replacement of the coil |
| A faint spark. | Inter-turn closure | Replacement of coil and candles |
| Break-through on the hull | Insulation crack, moisture | Drying, replacement, seal check |
Separately, it is worth mentioning the influence of spark plugs. If the gap in the candles is too large or they have not changed for a long time, the coil has to work with increased load, generating a higher voltage. This leads to overheating and premature failure of the ignition module.
βοΈ What to check before buying a new coil
Replacement of the coil and frequent errors
The process of replacing the ignition coil usually does not cause difficulties, but requires accuracy. In modern cars with individual coils (coil-on-plug), it is necessary to remove the plastic cover, disconnect the electric connector and unscrew the fastening bolt. After that, the coil is simply pulled out of the candle well.
One of the common mistakes is the use of unoriginal cheap analogues. Cheap Chinese copies can have unstable parameters and fail after a couple of thousand kilometers. It is better to choose proven brands, such as NGK, Bosch, Delphi Or original parts.
When installing a new part, make sure that it sat down to the point and fits tightly to the candle. The gap between the coil and the candle can lead to a breakdown and rapid failure of the new spare part. Also be sure to clean the candle well of oil and dirt before installation.
Always change spark plugs with the coils if the mileage on them exceeds 30-40 thousand kilometers to ensure stable operation of the new part.
After replacement, it is recommended to reset the errors in the ECU using a diagnostic scanner. Although the system can adapt itself, a forced reset will allow you to see the result immediately and make sure that the problem is solved. If the error comes back, you need to look deeper, perhaps in the wiring or the control unit itself.
Frequently Asked Questions (FAQ)
Can I drive with a faulty coil?
You can drive, but it is not recommended. Long-term operation will lead to the destruction of the catalyst due to the ingress of unburned fuel into the exhaust system, and can also damage the ECU. The engine will also be unstable, which is not safe on the road.
Why is the ignition coil warming?
Heating is a natural process when working, but excessive heating indicates overload. Causes: too large gap of candles, poor mass contact, internal closure of the windings or a malfunction of the ECU, which supplies too long a pulse.
How often do you need to change the coils?
The resource of the ignition coils is usually from 80 to 120 thousand kilometers. However, when using poor-quality fuel or rare replacement of candles, the service life can be reduced by half. You do not need to change them βjust in caseβ, only on the fact of malfunction.
Does the candle gap affect the operation of the coil?
Yeah, straight. The greater the gap, the higher the voltage must be created to break the spark. This creates an increased load on the secondary winding, accelerating its wear and increasing the risk of insulation breakdown.