Checking the Ignition Coil - 4 Effective Methods

The ignition coil in a car plays the role of an element that provides high voltage for the spark to form by a spark plug. It works on the principle of a step-up transformer. The operating principle determines the answer to the question of how to check the ignition coil for preventive purposes to avoid failure of automotive equipment or in the event of malfunctions.

Ignition coil device

The coil is a pulse step-up transformer. It is she who ensures the conversion of low voltage, which is supplied to it from the battery or generator, into high voltage pulses.

Thanks to these impulses, a spark jumps between the electrodes of the spark plug, which ignites the working mixture in the cylinders. Like any transformer, the coil consists of two windings (primary and secondary), a magnetic circuit and a housing.

The module is structurally somewhat more complex and includes two coils and a switch, but its operating principle is identical to the coil.

What faults cannot be diagnosed with an ohmmeter?

An ohmmeter can only diagnose an open or short circuit in the winding. An interturn short circuit in a winding will be barely noticeable when measuring resistance due to the small resistance of one turn and, as a consequence, a slight change in the total resistance when a short circuit between turns. An insulation breakdown between the turns of both one and different windings reveals itself only when this place is exposed to high voltage. It cannot be detected at all using a multimeter.

Therefore, if, as a result of checking with a multimeter, it was not possible to identify a defect, you need to resort to another proven method of detecting a faulty unit. You should replace all coils one by one with a known good one.

Why does contamination interfere with sparking?

The ignition coil, like any other transformer, increases the voltage of an electrical pulse, reduces its current. Contamination of the insulators of coils and spark plugs with oil and carbon deposits conducts electric current, and therefore can be represented in the form of a resistance connected in parallel to the spark gap and shunting it. The current flowing through this shunt from dirt and moisture greatly reduces the power of the electrical pulse applied to the spark gap. Therefore, the pulse voltage on the electrodes of the spark plug also drops, and it is not enough for a reliable breakdown of the interelectrode gap. Consequently, the higher the sparking voltage, the lower the pulse current, and the ignition system is more sensitive to various contaminants.

Principle of operation

The operation of the ignition coil is based on the principle of operation of a step-up transformer, when a small voltage of 12 V is converted into several thousand volts.

Voltage conversion occurs thanks to two windings - primary and secondary, which were mentioned above. In the first, a decreased U is created, in the second, an increased one.

Depending on the type of device, the location of the windings and their design differ.

Principle of operation:

The breaker closes the electrical circuit and voltage is supplied to the primary winding. Due to this, a magnetic field is generated in the coil.
After opening the circuit, the magnetic field disappears, but passing through the secondary winding it generates a high voltage in it.

The operating principle of the ignition coil is clearly presented in the video.
Coil types:

Regular.
Individual.
Two-terminal.

Regular ignition coil

Here the primary winding is a metal core (to increase the magnetic field) around which 150 turns of thin insulated copper wire are wound, the ends of which are brought out to the housing.

The secondary high voltage winding is a thin insulated copper wire wound around a metal core with up to 50,000 turns.

The second winding is connected to the first by negative wires. The positive wire of the high voltage winding is brought out to the cover and connected to a special terminal.

Some models of ignition coils contain transformer oil as an insulator and for cooling purposes.

Custom ignition coil

Their design is more complex than conventional coils; they are installed on engines with electronic injection.

Structurally, they also have two windings, which differ from each other not only in the number of turns and wire thickness, but also in the reverse order of winding.

So in the primary winding the core is located as usual inside, and in the secondary winding outside. Also in the secondary winding, in order to cut off very high voltage, a diode is provided.

Also, thanks to special design solutions, it became possible to supply high U not to the distributor, as is the case with a conventional coil, but directly to the spark plugs.

Two-pin

Such an ignition coil immediately supplies voltage to the spark plugs of two cylinders, i.e. on a four-cylinder engine there will be two of them and they will be combined into one block, which is essentially a four-terminal coil.

Causes of malfunctions

Ignition coils are reliable devices and the main reasons for their failure include: insulation breakdown, limiting service life.

Below we list other reasons why a device may fail.

1. Aging and mechanical damage.	During operation, the materials from which the ignition coil is made lose their strength, begin to crack and collapse, and various liquids (oil, antifreeze, etc.) can affect the device, which negatively affects its service life. There is only one solution - replacement.
2. Damage or oxidation of the contact connection.	Penetration of moisture under the hood, a humid climate, after fording, improper washing of the engine or car, all this can affect the condition of the contacts and their rapid oxidation.
3. Vibrations.	Individual ignition coils of electronic injection vehicles are very sensitive to vibrations. For example, if the motor is tripping, or one of its supports is out of order, it vibrates strongly. Also, very bad roads, which are not uncommon here, can cause severe shaking and affect the position of the reels.
4. Overheating.	The same applies to individual coils, which are located near the cylinder head, where the temperature is highest. In the intended temperature conditions of the engine operation, nothing will happen, but if, as a result of poor quality coolant or for other reasons, the engine overheats, this will negatively affect the ignition coil as a whole.

Replacement

Individual ignition coils should be replaced with similar models, otherwise there may be problems with ignition timing. It is also advisable to install dual and common ignition coils in accordance with reference data and equipment catalogs, especially since there are not many standard sizes of ignition coils.

Experienced auto electricians often replace the ignition coils of imported cars with domestic Zhiguli ones, and quite successfully. This does not in any way affect the driving performance of the car.

A factory coil from Lada costs two to three times less than a second-hand original or a new Chinese one. If there is a problem with the ignition coil, you can scour the Internet and find what can replace it. Only in this case, in most cases, you have to reconnect the connector to the coil. It is better to entrust this to a specialist.

To make the ignition coil last longer, follow these rules:

Wipe high-voltage wires regularly (preferably at the end of the seasons);
Make sure that the reel does not get wet or oily liquids;
check the quality of the coil connector, it should not spark or get hot;
change spark plugs regularly;
it must be firmly fixed in place, and not dangle;
at the slightest suspicion of a malfunction of the ignition coil (misfire, etc.), it should be tested immediately.

Remember, a faulty ignition coil leads to uneven operation, increased loads, and mechanical beats, which ultimately reduces engine life.

Video - VAZ ignition coil and its possible malfunctions:

Signs of breakdown

The reel has a reliable design and its service life is significant. And yet this element can also fail.

The main signs that the ignition coil is not working properly are:

Inability to start the power plant;
The inscription “Check Engine” appears on the dashboard (on cars with an ECU), and when scanning the system, code P0363 is displayed, indicating a malfunction of the ignition module (on modern injection cars);
Decrease in power unit performance;
Misfires, which causes the engine to “trouble” (with time the problem becomes more pronounced);
Dips when reaching certain crankshaft speeds.

It should be noted that these malfunctions are also typical for other elements of the ignition system, for example spark plugs, so before you “sin” the coil, you should check the entire circuit coming from it.

Other control methods

Using a multimeter allows you to determine the health of the coil, but this method is not always the most convenient. One of the easiest ways is to install, for example, on a 16-valve engine instead of dubious coils, proven ones. If a difference becomes noticeable during use, we can say for sure that the old part needs to be replaced.

On older models, the proper operation of the ignition was checked by trying to get a spark between the spark plug electrode and the housing. On modern cars, using this method can lead to unpredictable consequences.

If there is no spark in the spark plug, then the coil is not necessarily to blame. You need to check the appearance of the electrode contacts and clean them if necessary. They must be clean and dry.

You can check the operation of the ignition system using a spark. To do this you need to do the following:

Remove the high-voltage wire from the spark plug.
Place it at a distance of approximately 6 mm.
Rotate the crankshaft.
If you can visually observe a spark, then the ignition is working normally. Otherwise, the spark plugs must be cleaned or replaced.

A faulty ignition coil must be replaced with a new one, since it cannot be repaired. If there are deviations from the standard parameters, then during further operation this may lead to increased wear or breakdown of other components.

Finding the origin of the problem

First you need to check the performance of the spark plugs, and this check may indirectly indicate a coil malfunction.

To check, you just need to unscrew the spark plugs, insert them into the tips of the high voltage wires, massage them and turn the crankshaft several times with the starter. In this case, you should look at the spark that forms between the electrodes.

If it is discovered that a spark plug is not working correctly and the spark in it is formed intermittently, it should be replaced and a known good one installed in its place.

If a working spark plug works intermittently, check the high voltage wire.

If the interruptions persist even when the wire is replaced, then in carburetor cars the distributor is inspected next, and only then the coil.

In injection cars equipped with a module, there is no such distributor, so you can immediately start checking the module.

Checking these elements will not be particularly difficult, and the only equipment you will need is a multimeter with the ability to operate in ohmmeter mode, with a measurement range of up to 200 MOhm.

To make it more clear, let’s look at how these ignition elements are checked on different cars.

Checking the ICP with a spark gap

Procedure

Disconnect the IKZ from the spark plug.
Install a spark gap on the IKZ.
Apply ground (from the battery terminal) to the spark gap using a wire.
Turn the crankshaft with the starter.
If there is a spark, then the IKZ is working.

Let us remind you that you can find a problem in engine operation by independently measuring the pressure in the fuel rail, or by checking the compression in the cylinders.

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Basic Verification Approach

Since the windings play a key role in the operation of ignition coils, the first thing that needs to be checked, regardless of the type of device, is their resistance.

Thus, the resistance indicators of the primary winding can vary according to different data:

from 0.6 to 4 Ohm;
from 0.5 to 3.5 Ohm.

Secondary:

from 6 to 15 kOhm;
from 3 to 11 kOhm.

The indications are different because they can be different for each car model, so it is important to study the documentation for the car and the technical characteristics of the coil itself.

It is also important to understand that for each type of coil, indicators such as the inductance of the primary winding, the resistance of both windings, energy, duration and spark current may differ.

Measurements are performed with a multimeter or a regular ohmmeter.

If there is a strong deviation from the standard data, the ignition coil is most likely damaged. But there is no need to rush to change it; there are other ways to check.

How to check coils with a multimeter

In order for the procedure to be consistent and successful, it is worth studying in detail a number of special videos if you have absolutely no experience in carrying out such manipulations. Only after this can you begin practical actions. It must be remembered that carelessness, ignorance and inability can not only damage the coil itself, but also the structure of the entire engine. Then you will have to spend a lot of time and money to eliminate the problems that have arisen.

Tester selection

Experts from auto repair shops often use devices of the MAS 838 modification. They provide the ability to measure a regular microcurrent of 200 µA. The display is backlit, which means you won’t need to use a flashlight when working in a room with insufficient lighting to get the information you need.

Specific precision is not necessarily required to run the process itself . Therefore, for personal use there is no need to buy expensive models. The standard basic package is an ideal solution for the home handyman.

The non-contact ignition system operates while the magnet rotates, thus supplying alternating current. The device can operate over a wide temperature range.

The system itself is located in the space under the hood . It is very easy to ring it by touching the wires.

Professional testing

You will need professional grade equipment. The optimal solution would be to designate a separate stand for checking coils. This way it will be possible to set different speed modes for the rollers, simulating different types of work.

When interacting, you need to ensure that a spark is constantly maintained, regardless of the operating mode. Before carrying out the test, you need to make sure that this power supply is connected correctly, otherwise you may receive unreliable data, which will prevent the determination of problems.

A reel is a small component of vehicles. Even small deviations from normal performance can lead to serious engine problems.

Checking the coil for VAZ 2101-2110

First, let's look at the sequence of checks on VAZ cars. Moreover, checking the carburetor for VAZ-2101 and VAZ-2110 is no different, the only difference is in the readings.

Next is the verification process itself:

It is better to test the coil when it is removed from the car. Before starting removal, disconnect the negative terminal from the battery. From the coil we disconnect the wires from the side terminals, as well as the central wire. It is better to mark the wires from the side terminals so that they are not confused during installation.
Loosen the coil fastening and remove it. Before checking with a multimeter, we clean it from dust and dirt, especially paying attention to the terminals. Then we inspect it for external damage. If there are any, further checking is pointless; it is better to replace it immediately;
Checking the primary winding. To do this, switch the multimeter to ohmmeter mode and connect its probes to the side terminals. Different types of coils were used on different VAZ models, so you need to know which resistance readings are correct for them. So, for the B-117A model, used on classical models (VAZ-2101-2107), the resistance of the primary winding is 3.07-3.5 Ohms. And on classic models with a contactless system, coils marked 27.3705 are used; this parameter is 0.4-0.5 Ohm. On VAZ-2108-21099 cars, as well as VAZ-2110 carburetor, models with numbers are used - 3122.3705 and 8352.12. For the first of them, the resistance of the primary winding is considered normal in the range of 0.39-0.47 Ohms, and for the second - 0.37-047 Ohms;
Next, the secondary winding is checked. To do this, switch the multimeter to the kOhm measurement mode, leave one of its probes on the side terminal, and connect the second to the central terminal. For a working B-117A coil, the resistance of the secondary winding should be 7.4-9.2 kOhm. For model 27.3705 this parameter should be around 5.0 kOhm, for 3122.3705 - 0.4 kOhm, and for 8352.12 - 1.0 kOhm;
The last thing to check is the insulation resistance. To measure this parameter, switch the multimeter to measurement mode in MOhm. To measure, we connect one probe to the coil body, and connect the second to each terminal in turn. When measuring this parameter on all specified models, the multimeter should show at least 50 MOhm;
If any of the parameters does not match the specified values, then the coil is faulty and must be replaced.

Testing the ignition module on a VAZ-2110 injector

On injection cars, for example, VAZ-2110, the module check is performed slightly differently.

The check sequence is as follows:

We inspect the module for damage. Even small cracks can cause a module to fail, if not now, then in the near future. Therefore, such a module does not need to be checked, but replaced immediately.
Disconnect the block of wires going to the module. First, check the voltage supply to the module. To do this, switch the multimeter to voltmeter mode, connect one of its probes to terminal “A” (the letters are stamped on the block), and the second to “ground” and turn on the ignition. If the wiring is good, the voltmeter should show 12 V or close to it.
Then we take a 12 V test light and connect it to terminals “A” and “B” on the block. Then we turn on the starter and look at the “control”; it should blink when the starter is running.
We switch the multimeter to ohmmeter mode with the measurement parameter in kOhm and measure the resistance of the secondary winding of the coil at the paired terminals. To do this, we connect one probe to the terminal that supplies an impulse to cylinder 1, and the second to the terminal of cylinder 4. A working module should have a resistance of about 5,4
kOhm
We take another measurement, but now on terminals 2 and 3 of cylinders. The readings at these terminals should be normal. A strong discrepancy in resistance at paired terminals indicates a module malfunction and the need for repair or replacement.

Conclusion

Checking the health of the coil is a fairly simple task if you have some experience and some equipment. The simplest and most effective way for home use is to check the resistance of the coil windings using a multimeter. To improve convenience during operation, the coil should be removed from the machine.

If the coil turns out to be faulty, it is better to replace it with a new one. Repair, namely rewinding the windings, is a very expensive, time-consuming and thankless task. It is much easier and faster to buy and install a new one.