Diagnostics of the ignition system
Content
Often the reason that the car does not start is problems with its ignition system. In order to identify the problem, you need to ignition diagnostics. Sometimes it is not easy to do this, because, firstly, there is a large number of diagnosed nodes (problems can be in candles, various sensors, a distributor and other elements), and secondly, for this you need to use additional equipment - a motor tester, an ohmmeter, scanner to detect errors on machines equipped with an ECU. Let's look at these situations in more detail.
Vehicle ignition system
General recommendations in case of breakdown
Most often, breakdowns in the car ignition system are associated with a violation of the quality of electrical connections in the circuit, or current leakage in high-voltage wires. Let us briefly list what you first need to pay attention to if problems arise in the operation of the car’s ignition system, as well as what algorithm to act on.
- Check the state of charge of the battery with a voltmeter. The voltage on it must be at least 9,5 V. Otherwise, the battery must be charged or replaced.
- Check the quality of the contacts on the coil module on all spark plugs.
- Check all candles. They should not have significant black deposits, and the distance between the electrodes should be about 0,7 ... 1,0 mm.
- Remove and check the camshaft and crankshaft sensors. If necessary, they need to be replaced.
Most often, the problems lie in the violation of the quality of the contacts or the leakage of current in high-voltage wires. Check their insulation, condition of the ignition coil, ignition lock, coil fuse.
Common causes of malfunctions
Damaged high voltage ignition wire
Most often, breakdowns in the ignition system appear in the contact connections of electrical circuits, including high voltage wires. Often, due to the destruction of their insulation, a spark breaks through the body, which causes problems in the operation of the internal combustion engine. It is good to check the punched insulation of high-voltage wires in the dark. Then the emerging spark is clearly visible.
Always keep an eye on purity of insulation high voltage wires. The fact. that the oil that gets on their surface greatly softens the insulation, and attracts particles of dust and dirt to it, which can cause a spark breakdown.
On the insulators of the candles, “paths” may appear along which the breakdown passes. If the power does not fit to the high voltage wires, then you need to check the low voltage parts of the ignition system, namely, the voltage supply from the battery to the ignition coil. Possible malfunctions may be the ignition switch or a blown fuse.
Spark plug
spark plug electrodes
Often the causes of malfunctions in the system are problems with spark plugs. On a good candle:
- the electrodes on it are not burnt, and the gap between them is 0,7 ... 1,0 mm;
- no black soot, chips of the insulator on the body;
- there are no signs of burnout on the outer insulator of the candle, as well as cracks or mechanical damage.
You can read information on how to determine its condition by the soot of a candle and diagnose an internal combustion engine in a separate article.
Ignition misfires
Individual misfires can occur for two reasons:
- unstable contact connections or a non-permanent defect in the low-voltage part of the ignition system;
- breakdown of the high-voltage circuit of the ignition system or damage to the slider.
Slider and distributor cover
The reasons for the misfire may be breakdowns in the operation of the crankshaft and camshaft position sensors (you can see how to check the Hall sensor in a separate article).
On carbureted cars, the problem is distributor cover. Often cracks or damage appear on it. Diagnostics must be performed on both sides, after wiping it from dust and dirt. It is necessary to pay attention to the possible presence of cracks, carbon tracks, burnt contacts and other defects. you also need to check the condition of the brushes, and the tightness of their pressing against the contact surface of the slider. At the end of the revision, it is advisable to spray the surface of the system with a desiccant.
Ignition coil
A common cause of problems in the system is the ignition coil (hereinafter short circuit). Its task is the formation of a high-voltage discharge on the spark plug. Coils are structurally different. Older machines used coils with a single winding, more modern ones used twin or monolithic modules containing high-voltage wires and lugs. Currently, coils are most often installed for each cylinder. They are mounted on candles, their design does not provide for the use of high-voltage wires and tips.
Ignition coil
On old cars, where a short circuit was installed in a single copy, its failure (winding breakage or short circuit in it) automatically led to the fact that the car simply did not start. On modern cars, in the event of problems on one of the coils, the internal combustion engine begins to “troit”.
You can diagnose the ignition coil in various ways:
- visual inspection;
- using an ohmmeter;
- using a motor tester (oscilloscope).
During visual inspection, it is necessary to carefully examine the current-insulating parts. They should not have traces of soot, as well as cracks. If during the inspection you have identified such defects, this means that the coil must definitely be replaced.
Diagnostics of ignition malfunctions involves measuring the insulation resistance on the primary and secondary windings of the ignition coil. You can measure it with an ohmmeter (multimeter operating in resistance measurement mode), by making measurements at the terminals of the windings.
detailed information on checking is presented in the article on how to check the ignition coil. And the most accurate and perfect method for diagnosing the ignition coil and the entire system is carried out using a motor tester (oscilloscope).
Diagnostics of the ignition module
ICE ignition module
The mentioned diagnostics should be carried out when the following malfunctions occur:
- unstable idling of the internal combustion engine;
- motor failures in acceleration mode;
- ICE triples or doubles.
Ideally, a professional scanner and a motor tester should be used to diagnose the ignition module. However, since this equipment is expensive and is used only in professional service stations, it remains possible for an ordinary driver to check the ignition module only with improvised means. Namely, there are three verification methods:
- Replacing the module with a known working one. However, there are a number of problems here. The first is the lack of a donor car. The second is that the other module must be exactly the same as the one being checked. Third - high-voltage wires must be known to be in good condition. Therefore, this method is rarely used.
- Module shaking method. To diagnose the node, you just need to move the block of wires, as well as the module itself. If at the same time the operating mode of the internal combustion engine changes noticeably, this means that somewhere there is a bad contact that needs to be corrected.
- Resistance measurement. To do this, you will need an ohmmeter (a multimeter that works in electrical resistance measurement mode). The probes of the device measure the resistance at the terminals between 1 and 4, and also 2 and 3 cylinders. The resistance value must be the same. As for its size, it can be different for different machines. For example, for a VAZ-2114, this value should be in the region of 5,4 kOhm.
Electronic control system DVSm
Almost all modern cars are equipped with an electronic control unit (ECU). It automatically selects the optimal operating parameters for the internal combustion engine based on the information received from the sensors. With its help, you can diagnose the breakdowns that have occurred in various machine systems, including the ignition system. For diagnostics, you need to connect a special scanner, which, in the event of an error, will show you its code. Often, an error in the operation of the system can occur due to a breakdown of one of the electronic sensors that provide information to the computer. An electronic scanner will inform you about the error.
Diagnostics of the ignition system using an oscilloscope
Often, when professionally checking the ignition system of a car, a device called a motor tester is used. Its basic task is to monitor the high voltage waveform in the ignition system. In addition, using this device, you can view the following operating parameters in real time:
A complete set of motor tester for car diagnostics
- spark voltage;
- time of existence of a spark;
- breakdown voltage of the spark.
All information is displayed on the screen in the form of an oscillogram on the computer screen, which gives a comprehensive picture of the performance of candles and other elements of the car's ignition system. Depending on the ignition system, diagnostics is carried out according to different algorithms.
namely, classic (distributor), individual and DIS ignition systems are checked using an oscilloscope in different ways. You can find detailed instructions on this in a separate article on checking the ignition with an oscilloscope.
Conclusions
breakdowns in the ignition system of a car can sometimes turn into big problems at the most inopportune moment. Therefore, we recommend that you periodically inspect its basic elements (spark plugs, high-voltage wires, ignition coils). This check is simple, and quite within the power of even an inexperienced motorist. And in the event of complex breakdowns, we recommend that you seek help from a service station in order to carry out detailed diagnostics using a motor tester and other diagnostic equipment.
