How to check the ignition coil for serviceability?

The operation of a gasoline internal combustion engine is impossible without an ignition coil (KZ). It is she who produces high voltage to form a full ignition spark. This has remained unchanged since the appearance of the car, despite the fact that the coil itself underwent a significant transformation during this time. But as before, when the spark disappears, it first of all comes under suspicion. Therefore, even the owner of a modern car needs to know how to check the ignition coil and what symptoms will occur if it is damaged.

KZ design

Any ignition coil is primarily a high-voltage transformer consisting of two windings. One of them, the primary one, receives low voltage pulses. It is wound with a wire of large cross section and contains a minimum number of turns (about 150). Therefore, its resistance is not enough.

Another winding is called secondary, high voltage is induced on it, causing sparking in the cylinders. The cross section of the wires of this winding is tenths of a millimeter, and the number of turns is several thousand. Accordingly, and her resistance is quite large - a few kilo-ohms. Specific figures do not yet matter. The main thing to remember is that the primary winding is a few ohms, and the secondary is a few ohms. This will come in handy in the future, since it is possible to check the serviceability of the ignition coil only by measuring its resistance.

Varieties of KZ

The ignition system of the car was improved simultaneously with the modernization of the engine. At the moment, there are three main types of short circuit:

1. Classical, it is also called a "bobbin". It was installed on carburetor cars until the cessation of their production.
2. Ignition module. It is still installed on some models of modern cars, most often domestic.
3. Individual reel. Most often responsible for sparking in 16 valve engines.

All KZ has one thing in common - purpose. Even in the most modern engine, designers could not do without high voltage. Their device is different, and the method of checking one can be absolutely useless when diagnosing another. Moreover, sometimes this can cause a fault in the short circuit. Therefore, before checking the ignition coil, you need to make sure that this diagnostic method is applicable to it.

Typical malfunctions

The coil is a fairly reliable element, it rarely fails. At the same Togliatti classics, the KZ often “survived” the engine itself. However, for various reasons, the coil sometimes breaks. You can find out by the following symptoms:

• the engine is troit, i.e. misfires are observed in the cylinders, and they periodically do not work;
• on the injection vehicle, the check engine lights up;
• engine power loss is observed;
• the engine does not start, this symptom is characteristic only for carburetor cars;
• the engine becomes "gluttonous", average fuel consumption can increase by more than 10%;
• starting the engine in severe frosts is difficult;
• on vehicles with an ignition module, the failure of two cylinders at once.

With a high degree of probability, it is possible to assume a coil malfunction only in the latter case. All other symptoms are characteristic of many other nodes. Therefore, when they occur, you need to check both the ignition coil and the rest of the system elements.

Reasons for Failure

Non-compliance with the operating rules is the main reason for buying a new coil. This happens in the following cases:

1. Use of low-quality or not designed spark plugs for this type of engine.
2. Unprofessional washing of the engine can cause the secondary winding to short-circuit to its housing.
3. Overheat. The potential inherent in the designers allows the coils to work at high temperatures. However, cases of short circuit damage due to overheating are not so rare.

The last paragraph requires a short explanation. Overheating of the coil can occur not only due to the high temperature in the engine compartment. Sometimes it is caused by an oil leak and a short circuit in the secondary winding. Therefore, if there is a suspicion of overheating, it is necessary to check the ignition coil both for tightness and for the absence of conductivity between the turns.

A few words about the multimeter

This device must be purchased or borrowed from someone. Despite the fact that you can check the ignition coil with both a multimeter and a conventional tester, the latter is undesirable. Its accuracy is insufficient, and more skills will be required. An ordinary Chinese multimeter is more suitable for checking a coil.

Of the many modes of the device, only one will be used - resistance measurement. The multimeter has several ranges for this. When checking the coil, only three are needed: 200 Ohms and 20 kOhms, and 2000 kOhms. This is enough to get accurate measurements. Now you can go directly to the process of checking each of the three varieties of coils.

Diagnostics of the "classic" short circuit

This does not mean that we will talk about how to check the ignition coil of the VAZ 2101-2107. "Classic", in the sense of having the most conventional design, in other words, the one that was installed on carburetor engines. The check is carried out for a break in the primary and secondary windings and a short to the case.

The coil has three outputs. Two of them are marked with the signs "+" and "-", the third is the central one, the main high-voltage wire is inserted into it. Check the coil in the following order:

1. Set the multimeter switch to 200 Ohm. The indicator should show the number 1.
2. Connect the probes to each other. On the screen - the error of the multimeter, it is important to consider it when measuring small resistances.
3. Disconnect the wires from the terminals and the central contact.
4. Set the probes to the terminals "+" and "-", the polarity does not matter.
5. Indications of the device, taking into account the error, should be in the range of 0.5-2 Ohms.
6. Now you need to measure the secondary winding.
7. The device is set to 20 kOhm.
8. Install the multimeter probes on the "-" terminal and on the central contact.
9. The normal value is 6-8 kOhm. Sometimes it can reach 12 kOhm. In any case, there should not be a cliff.
10. Set the switch to 2000 kOhm.
11. The probes put on the "mass" of the car and the central contact.
12. The appliance should show 1. This means that there is no leak.

Ignition Module Test

This device is installed on cars with an injection engine, mainly on the domestic VAZ. Its peculiarity lies in the simultaneous supply of a spark: immediately to two cylinders 1 and 4, 2 and 3. Troubleshooting in this case is greatly simplified. If the corresponding cylinder pair does not work, a module malfunction is diagnosed. In the vast majority of cases, this is true, but sometimes, however, extremely rarely, the entire module fails. In this case, you will have to check the ignition coil of the VAZ injector with a multimeter. To do this, you must:

1. Disconnect the connector from the module and pull out the high-voltage wires.
2. Set the switch to 200 Ohm.
3. Alternately measure the resistance between the middle and extreme pins of the connector.
4. Instrument readings should be within 0.5 ohms. In this case, it is necessary to take into account its error.
5. Now you need to measure the resistance of the secondary windings. It is necessary to sequentially install the probes between the high-voltage terminals of the first and fourth, and then 2 and 3 cylinders.
6. Set the mode switch to 20 kOhm.
7. The device must show a resistance of the order of 5.4 kOhm.

Checking individual short circuit

Coils of this type are installed on each candle, hence the name. Thus, not only was it possible to get rid of unreliable high-voltage wires, but the most important thing was to significantly increase the efficiency of each of them. Therefore, most often they are installed on 16-valve engines. A distinctive feature of individual coils is the high resistance of the secondary winding. This must be taken into account before checking the ignition coil of a 16-valve engine with a multimeter. You may need to use a larger measurement limit. The verification sequence is as follows:

1. Remove the contact block from the coil.
2. The device switch is set to 200 Ohm.
3. We measure the resistance between the extreme contacts of the coil, it should be within 1 Ohm.
4. Now you need to transfer the device to the 2000 kΩ range and install the probes on the middle terminal of the terminal and the contact inside the rubber cap.
5. Resistance should be 300-400 kOhm.
6. Thus, you need to check each coil. There should not be significant differences in the readings of the device.

Measurement Features

The measurements of the primary and secondary coils given here are rather arbitrary. Firstly, a household multimeter is clearly not enough to measure a value of the order of 1 Ohm. This does not mean that it cannot be used. The presence of interturn circuit in the primary winding can be detected only by complex laboratory devices. At the same time, it will also be possible to establish its integrity with a multimeter, and this is quite enough for diagnosis.

Secondly, the resistance of the secondary winding may vary depending on the type of coil and the make of the car. Therefore, before checking the ignition coil on the "Prior", "Grant", and other cars of domestic and foreign production, you must refer to the manual to clarify the relevant data.