The internal combustion engine is a complex mechanism where each element plays a critical role, but it is the ignition system that often becomes the weak link when the first symptoms of malfunction appear. When a driver notices that the car has started to twitch, twitch when accelerating or just consume more fuel, the first thing that comes to mind an experienced mechanic is the state of mind. spark-plug. These small but incredibly important parts are responsible for the ignition of the fuel-air mixture, and the slightest failure in their work instantly affects the dynamics and economy of the machine.
To understand that the candle is out of order, is not always possible without visual inspection, but there are indirect signs that can not be ignored. iridium or platinum candles, despite their increased resource, are also subject to electrode degradation and contamination. Ignoring early symptoms can lead to more serious problems with the disease. catalytic converter or even the failure of the ignition coils, the repair of which will cost much more.
In this article, we will discuss in detail all aspects of diagnosis: from the behavior of the car on the road to the analysis of the color of the soda on the insulator. You will learn to distinguish between normal and critical and will understand when replacement is inevitable. It is important to approach the issue comprehensively, as one faulty part can mask problems in related systems, such as: fuel-nozzle or GRV valves.
Symptoms of failure of spark plugs during operation
The first bells that the element of the ignition system requires attention, the driver notices even before opening the hood. The most striking manifestation of the problems is the unstable operation of the engine at idling. The motor begins to vibrate stronger than usual, the tachometer arrow can jump chaotically, and a characteristic hum appears in the cabin. This is because the mixture in one or more cylinders does not burn completely or does not ignite at all, which leads to an imbalance in the work. crank-and-wheeler.
Another classic sign is the loss of traction and dips when pressing the accelerator pedal. If you feel the car has become sluggish, is not gaining speed well or twitching when trying to overtake, then most likely the spark is too weak or absent. In modern cars with electronic control unit (ECU), this is often accompanied by a lighting indicator. Check Engine on the dashboard. The self-diagnosis system records ignition skips and reports it to the driver, although a scanner will still be required to pinpoint the cause accurately.
The sharply increased fuel consumption may also indicate the wear of candles. When the spark is unstable, the ECU tries to compensate for the poor combustion by enriching the mixture, which leads to overconsumption of gasoline or diesel. In addition, you may notice a change in the sound of the exhaust: it becomes louder, intermittent, sometimes with characteristic claps. In the cold season, difficult engine start, especially after a short parking, is also often hidden in the state of the engine. central electrode.
⚠️ Warning: Prolonged operation of a car with faulty candles can lead to a breakdown of high-voltage wires or failure of expensive ignition coils due to increased resistance in the circuit.
Do not ignore the smell of unburned fuel from the exhaust pipe. If the gasoline does not ignite in the cylinder, it enters the exhaust manifold, where it can burn out, emitting an unpleasant aroma and damaging the catalyst honeycombs. Visually, this may be accompanied by black smoke from the exhaust pipe. Timely diagnosis will help to avoid costly repair of the vehicle’s environmental systems.
Visual diagnosis: analysis of the color and condition of nagar
The most accurate way to know if a candle is out of order is to dismantle it and make a thorough visual inspection. The color of the coar on the central electrode insulator can tell an experienced diagnostician about the processes occurring inside the cylinder, no worse than any computer scanner. Normal is the condition when the insulator has a light brown, coffee or grayish brown hue. This indicates the correct ratio of fuel and air, as well as the serviceability of the ignition system and the absence of problems with the air. compression.
If you find a black, dry, soot plaque resembling velvet, this indicates the engine is working on a too rich mixture. The reasons may lie in malfunctions nozzleA contaminated air filter or an oxygen sensor problem. In this case, the candle itself may still be working, but the conditions of its operation are violated. Frequent driving in urban mode with short trips also contributes to the formation of such a raid, which eventually begins to conduct current, causing skips spark.
The white or light gray color of the insulator, especially if it looks melted or has a vitreous surface, indicates overheating of the engine. This may be due to the use of fuel with a low octane number, too early ignition or violation of the thermal regime. Overheating is dangerous because it can lead to kalyl ignition, when the mixture is ignited not from a spark, but from hot parts, which is fraught with serious damage. piston-group.
Oily black coating with a brilliant shade is an alarm signal indicating that oil enters the combustion chamber. This occurs when the oil caps, rings or valves guiding the bushing are worn. In such a situation, the replacement of candles will only give a temporary effect, since after a short time they will again be covered with oil and stop working. It requires serious engine repair, and not just maintenance of the ignition system.
What does a red plaque on a candle mean?
Red or brick shade of the insulator appears when using fuel with a high content of metal additives (ferrocenes). Such a plaque is conductive and can cause ignition misses. It is recommended to change the gas station and clean the candles if the stain has not been absorbed into the structure of ceramics.
Table of color indicators of the state of the engine
To systematize the data obtained during the inspection, it is convenient to use a summary table. It will help to quickly compare visual signs with the probable causes of malfunction. Remember that the condition of each candle in the kit may be different, and this is also a diagnostic sign indicating problems in a particular cylinder.
| Color/State | Probable cause | Recommended action | Resource impact |
|---|---|---|---|
| Light brown/Gray | Normal work, proper mixing | Continue operation | Standard. |
| Black dry (soot) | Rich mixture, problems with air or nozzles | Check DMRV, nozzles, filter | Reduced (oiling) |
| White/Melted | Overheating, poor mix, early ignition | Check the cooling system, octane number | Critical (risk of burnout) |
| Oily black | Wear of CPG or oil caps | Diagnosis of compression, engine repair | Quick outage |
| Red plaque | Fuel additives (ferrocene) | Change the gas station, clean or replace | Medium (skipping spark) |
When analyzing the table, it is important to consider not only the color, but also the gap between the electrodes. If the gap is increased above the norm specified by the manufacturer, the spark becomes harder to penetrate the air gap, which increases the load on the coil. Too little clearance is also undesirable, as the spark will be weak and may not ignite the mixture effectively. Optimal values are usually in the range from 0.7 to 1.1 mm, but for each engine model they are individual and prescribed in the following categories: technical documentation.
The color of the insulator is the “medical map” of the engine: brown – health, black – a rich mixture, white – overheating, oil – wear of the engine.
Checking the clearance and integrity of the insulator
In addition to color, a critical parameter is the physical condition of the electrode and the ceramic insulator. During operation, metal erosion occurs: spark discharge gradually burns out the electrode material, increasing the distance between them. To check the gap, you need to use a special tool - a probe or a set of flat probes. To make measurements "by eye" is strictly prohibited, since the error even a few tenths of a millimeter significantly affects the quality of spark formation.
Carefully examine the ceramic part of the candle for the presence of microcracks or chips. Even a barely noticeable crack in the insulator can become a channel for high voltage leakage. In this case, the spark will not be pierced between the electrodes, but on the surface of the ceramic or on the body ("the mass"). This phenomenon is often difficult to diagnose visually with a running engine, as the candle may look whole but not perform its function under load.
Pay special attention to the side electrode. If it has traces of corrosion, is very thin or, conversely, is framed by a thick layer of sodium, its effectiveness is in question. Sometimes the soda can form a "bridge" between the central and lateral electrode, completely closing the chain and eliminating spark formation. In such cases, the candle can be cleaned with a sandblaster, but if the erosion of the metal is large, it will only help. replacement.
☑️ Diagnostics of gap and insulator
Methods of checking spark and resistance
If the visual examination did not give a clear answer, it is necessary to move to more accurate diagnostic methods. The easiest, but not always reliable way is to check the spark "for the masses". To do this, the twisted candle is applied with a metal part of the thread to the engine (mass) and spin the starter, watching the spark slip between the electrodes. However, this method does not show the quality of the spark under pressure, since the ignition conditions in the cylinder are much tougher than in the open air.
A more professional approach involves the use of a special spark plug tester or oscilloscope. These devices allow you to assess the power of the spark, the duration of the pulse and the stability of the discharge. It is also important to check the resistance of the candle itself (for resistive types) and the resistance of high-voltage wires or coil tips. The inconsistency of resistance to the nominal values specified by the manufacturer indicates a violation of the conductive properties of the element.
There is an exclusion method that is often used in garage conditions. If the engine is triple, you can alternately remove connectors from the ignition coils (on injector cars) or caps (on contact systems) with the engine running. If when you turn off a serviceable cylinder, the engine performance deteriorates, and when you turn off the problem one, it does not change, then you have found the source of the malfunction. However, this method requires caution not to get electrocuted and not to damage the electronics.
⚠️ Warning: When checking the spark, never hold on to a metal candle body or high-voltage wire with your hands to avoid electric shock, the voltage in the ignition system reaches 20-40 thousand volts.
For modern systems with individual coils (Coil-on-Plug) often used the method of permutation. The candle and coil from the problem cylinder are rearranged into another, obviously serviceable cylinder. If the error (ignition misses) "moved" along with the detail, then it is in it. If the error remains in place, the problem should be looked for in the fuel system or engine mechanics of this cylinder.
Resource of operation and selection of new candles
Each spark plug has its own regulated service life, which depends on the material of the electrodes and operating conditions. Ordinary nickel candles serve an average of 20-30 thousand kilometers, while platinum and iridium analogues are able to travel from 60 to 100 thousand kilometers or more. However, these figures are relevant only for ideal conditions: high-quality fuel, a serviceable engine and mainly a track mode of driving.
In a real urban cycle, when the engine often runs at idle speeds or in start-stop mode, the candle life is reduced by almost half. The accumulation of sodium occurs faster, and the heat load changes more chaoticly. Therefore, experienced auto mechanics recommend that you carry out a preventive check and cleaning of candles every 15 thousand kilometers, even if there are no visible symptoms of malfunction.
When choosing new candles, it is critically important to follow the parameters specified by the car manufacturer. Key characteristics are the kalyl number (thermal characteristic), thread, length of the threaded part and size turnkey. Installation of candles with an inappropriate potassium number can lead to either rapid fouling with soda (if the candle is “cold”), or detonation and tanning (if the candle is “hot”).
Buy candles only in checked stores and check for holograms on the package, as the market is oversaturated with counterfeit products that can disable the ignition coils in a few days.
Replacing candles is a procedure that requires care. It is necessary to screw new elements with the observance of the tightening moment, using a dynamometer key. Retraction can lead to the failure of the thread in the head of the cylinder block, and undertwistling - to loss of tightness and overheating of the candle. After installation, it is recommended to give the engine to work at idle speeds for several minutes so that the system adapts to the new parameters of spark formation.
Frequently Asked Questions (FAQ)
Can I drive if the engine is on a single candle?
Long driving with a trembling engine is extremely undesirable. Unburned fuel enters the catalyst, where it continues to burn, causing it to overheat and melt the honeycombs. In addition, gasoline washes the oil film from the walls of the cylinder, increasing the wear of the piston group, and unbalanced operation of the engine creates additional vibration on the crankshaft.
Why are new candles quickly covered with black soda?
Black soak on new candles almost always indicates external factors: poor fuel quality, malfunction of the air supply system (air sucker or dirty filter) or problems with nozzles (overflow). Also, the cause may be the wrong thermal regime of the engine or too frequent driving for short distances without warming up.
Do I need to lubricate the candle carving before installation?
Absolutely not. Modern candles have a special graphite or other coating of threads, which prevents boiling. The use of copper lubricant or antifriction formulations can change the timing of the tightening, cause the thread to overheat, or make subsequent unscrewing difficult due to coking the lubricant at high temperatures.
How often should I change candles on gas cylinder equipment (GBO)?
When working on gas, the combustion temperature is higher and the mixture is drier, which leads to more intense electrode erosion. The resource of candles on HBO is reduced by about 30-40% compared to the gasoline regime. It is recommended to use special candles for HBO with a reduced gap and check their condition every 10-15 thousand kilometers.