Sooner or later, all motorists are faced with the next problem of replacing spark plugs. And those who are not accustomed to the services of auto mechanics and prefer to solve problems on their own very often witness the formation of dirt on the spark plugs. Yellow deposits on the spark plug insulator or brown deposits on spark plugs occur for certain reasons and are often of different natures. In this article, we will try to understand them, and also explain how to avoid such a fate in the future.
Causes of soot
The normal service life of spark plugs is 50 thousand km. Once this milestone is reached, they must be replaced. This is a normal result and cannot be avoided. An interesting fact: you can take excellent care of your car, but plaque will still appear. Their normal color is grey. Minor changes are not scary if the electrodes do not have visible damage. If plaque appears on new spark plugs, then you need to look for the reasons.
Causes of soot formation - why does this happen?
Spark plugs in an internal combustion engine perform the function of timely ignition of the fuel-air mixture. With their help, a spark is created, which ignites the fuel. Due to their design features, the lower part of the spark plugs is always located directly in the combustion chamber of the engine, which is why they experience enormous temperature loads, are subject to constantly high pressure and various chemical processes.
Therefore, over time, carbon deposits form in the lower part of the spark plug, on the insulator or electrodes, and various deposits and darkening may also appear. On a working engine with high-quality spark plugs, carbon deposits, as a rule, have a gray tint. It coats them in an even, dry and light layer. This situation is absolutely normal, especially if the spark plugs have already “run” more than 50 thousand kilometers.
If there are problems with the engine and related systems, the color of the spark plugs may change, and an uncharacteristic dry or spotty coating of red, white or black color begins to form on it. If, after unscrewing the spark plugs on the engine of your car, you find such deposits, you should diagnose the engine, check the ignition timing (ignition timing), the set gaps and other possible causes of deposits, which we will discuss in more detail below.
conclusions
Analysis of this problem and the experience of motorists suggest that visual diagnosis of spark plugs covered with soot is an excellent method not to miss the onset of problems with the car’s fuel system. You need to not be lazy and inspect these parts from time to time. In addition, do not forget that protective gear has its own service life, and when plaque appears, this is the first thing to check. If necessary, the spark plugs must be replaced and only then proceed with initial engine diagnostics.
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The engine is the heart of any car, and spark plugs are, of course, one of the main indicators of its proper operation. It is because of their malfunction that the engine may not start at all. The most common problem with candles is black soot. If it appears, the driver’s main task will be to identify and eliminate the cause, since this determines the performance of the vehicle.
What color is considered normal?
The performance of the gasoline power unit is indicated by spark plug electrodes painted in a light brown tint, without oil deposits and soot. A similar picture is observed in completely new engines and engines that have undergone a major overhaul.
If the color of the working part differs from the specified one, it is advisable to carry out further diagnostics and identify the cause of the problem. Moreover, the engine itself is not always the culprit. What color options are there for spark electrodes:
- light gray or white;
- black;
- brick or frankly red tint.
In addition to all sorts of colors, the candle skirt is covered with various deposits - soot, brown soot, or may simply look wet. These phenomena are also considered signs of various malfunctions. It is proposed to consider each situation in more detail.
Types of carbon deposits on spark plugs
So, the car has driven a certain distance (15-20 km), and if, after unscrewing the spark plugs, it is discovered that the electrodes are light brown, “brick” (the color of red brick), then everything is in order with the engine - the systems are functioning normally, the processes in the chambers combustion is not disturbed.
But this shade does not always happen. Often, after unscrewing, it is discovered that the candles have the following color:
- Black;
- White;
- Red.
In addition to carbon deposits of different colors, traces can be found on the electrodes:
- Gasoline;
- Oils;
- Ash deposits;
- Erosion.
And every discrepancy with the norm has its own reasons. Therefore, a simple inspection of the spark plugs can help in identifying malfunctions or malfunctions of systems and mechanisms, and at an early stage and eliminating them before serious problems arise.
Reasons for the formation of plaque and soot on candles
Black soot and the reasons for its appearance
As already noted, black soot is a consequence of feeding an enriched mixture. But if before the power plant reaches the optimal temperature regime, this mixture ratio is normal, then the detection of velvety black deposits on the electrodes after a long trip indicates the emergence of problems in the operation of the power system. This can happen due to:
- incorrect carburetor adjustment;
- failure in the injection engine ECU;
- sensor malfunctions (as a result of which the control unit begins to operate in emergency mode);
- severely clogged air filter.
A table showing the types of carbon deposits on candles and the reasons for their appearance.
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White deposits on spark plugs
The white coating on the electrodes of the spark plugs is caused by a very lean mixture. This mixture formation is also incorrect, and it can subsequently lead to very serious problems. Because of this, the combustion process is disrupted, accompanied by the release of increased heat. And this leads to overheating of the combustion chamber, the likelihood of melting of the electrodes and valve edges.
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In a carburetor engine, a lean mixture often occurs due to air leaks in the power system; in an injection engine, such deposits cause the same malfunction in the operation of the ECU. Additionally, the cause of the white color of the spark plugs may be low-quality gasoline. Such deposits are also caused by problems in the ignition system, or more precisely, by a mismatch in the ignition timing.
Red electrodes
Red carbon deposits on candles are not a very common occurrence, and the reason for its appearance lies in gasoline. Unclean fuel suppliers add additives based on metal compounds (most often lead) to gasoline to increase the octane number. During combustion in the cylinders, these additives oxidize and settle in the form of red carbon deposits. In this case, the spark formation of the spark plugs is disrupted, which causes interruptions in the operation of the power plant.
These additives also have a negative effect on other components, therefore, if such deposits are detected, it is not enough to change gasoline; it is advisable to conduct a more in-depth diagnosis of the condition of the power plant using specialized diagnostic equipment.
White deposits on spark plugs
When diagnosing spark plugs, many car enthusiasts expect to see black resinous deposits, soot or something worse, but in 20% of cases the deposits can be white. White deposits on the spark plugs indicate problems with fuel quality and a significant decrease in fuel in the combustion mixture; if the white deposit is a little rough to the touch, if the deposit is glossy, the cause is frequent overheating of the engine. In the first case, the problem is almost non-existent, you just need to clean the spark plug and install it back, it wouldn’t hurt to also change the gas station and gasoline to a high-quality one, in the second case, cleaning is not enough. The main causes of overheating may be:
- Provided that the spark plug is not suitable for this type of engine;
- The inlet pipeline is depressurized, which is why air is often taken in from outside;
- Problems with the cooling system, most often due to untimely replacement of the cooling element;
- Problems with the radiator;
- Poor ignition calibration.
Quite often it happens that the surface does not have a white coating, but a slightly yellowish one, which is typical for problems with an increase in temperature in the combustion chamber when the engine is running at maximum speed. To prevent overheating, you should change gears before the engine reaches 4,000-5,000 rpm.
How to correctly assess the condition of spark plugs
Plaque on spark plugs, which forms during operation of a car, can provide fairly accurate information, but the test must be carried out in compliance with a number of rules:
- You can evaluate the plaque only after a run of 150–200 km, always with new or well-cleaned SZ.
- Don’t panic if, during the cold season, you hear slight interruptions in the engine’s operation, and at low speeds the ignition elements become covered with a black coating. This is the result of the fact that at low temperatures the working mixture undergoes mandatory enrichment, which, if the engine is slightly warmed up, will not be able to burn completely. If there are repeated interruptions in the operation of the motor, it is worth paying special attention to the condition of the high-voltage wires.
- When visually diagnosing elements, it is worth remembering that they can self-clean only at high temperatures, which are only possible when the engine is running at high speeds.
What do the different colors of carbon deposits on spark plugs indicate?
Before your trip, don’t be lazy to check the spark plugs. But after warming up the car, you should not turn it off and take them out for inspection; this is a dubious method. A warm engine is greatly enriched in the combustible mixture, and it starts quickly. An oily coating forms on them, but it disappears when passing a certain distance. Inspect them after you have driven more than 200 km. If you take this as a rule, you can avoid breakdowns and eliminate the first manifestations of the problem in a timely manner. Remember that the normal color is light brown. There should be no traces of oil or carbon deposits. If the color is different, there is a problem and the cause needs to be determined.
Is a brown rim good or bad?
It appears on the ceramic insulator, immediately after the metal body of the spark plug. It can be larger or smaller, taller or shorter. Lighter or darker. Look at this one on my candles.
I want to reassure everyone right away - in general, it does not carry any semantic meaning . Whether it is there or not, the candle works as before.
This brown rim or coating (some call it soot) does NOT carry any negativity!
This is not a breakdown of the housing, not an upward breakthrough of gases, this is a little different.
How can you check spark plugs?
Agree that most of us check spark plugs when the first causes of their problems occur. Naturally, this is not the right move for an owner monitoring the operation of his vehicle.
Check the condition of the spark plugs every 5-8 kilometers.
How to eliminate white plaque?
Cleaning spark plugs
One of the most popular methods for eliminating white residue on spark plugs is manual cleaning. But please note that at home, the risk of damaging the insulating coating of the motor is very high. It is worth adding that on damaged insulators, a white coating settles more often than on intact and undamaged ones. Also, do not clean candles with hard or sharp materials. Special brushes or tapes with long and thin connecting wires are best suited.
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Corona discharge
This is all due to a physical phenomenon called corona discharge.
I’ll try to explain “on the fingers” what it is.
The spark plug well, as I wrote above, is closed on 16 valve engines. The top is covered by a rubber seal for the ignition coil.
That is, the space from the spark plug (its installation location) to the top (the ignition coil) is closed and has, as it were, “trapped air” inside. From high voltage, it begins to ionize. A blue discharge (glow) begins to form on the body of the spark plug - this is what we call “corona”.
Particles that are inside this enclosed space begin to stick to the body (one might say become magnetized). And often there may be dust, dirt, oil (which forms into oil mist). This whole thing settles on the insulator, forming a brown rim. You need to understand that this is a normal physical phenomenon.
Soot color - what does it mean and what to do?
Take a close look at the spark plugs. Their color will help you understand a lot... For example, you will be able to identify problem areas of the car. It is not enough to just replace the problematic element; look deeper and look for the cause. If it is not corrected, the new spark plug will very quickly become unusable. The problem needs to be cut to the root. The first step is to deal with the ignition system. The next step is to look at the candles. Determine what color the resulting plaque is. Highlight:
- black
- red
- white
Each of them indicates the presence of one or another problem.
Black soot
This type of soot occurs for a number of reasons. There are two subspecies:
- Dry;
- Oily.
Black and dry carbon deposits are applied to the spark plug due to an overly enriched mixture. This could have been preceded by:
- Incorrect carburetor operation;
- Air filter clogged;
- High pressure in the fuel rail;
- Little spark energy;
- Weak compression.
If an oily deposit appears, check that the oil does not get into the combustible mixture. Often the reason is trivial - wear of the oil scraper piston rings. Damage to the valve caps can also affect this.
White plaque
This color appears due to a number of reasons. White deposits on spark plugs can have several shades. Slightly ashy appears when the engine runs on low-quality gasoline. To overcome the problem, remove them, wipe them and they are usable again. Well, monitor the quality of gasoline. But the appearance of shiny soot and erosion on the contact electrodes is a sign of the use of overheated spark plugs. This happens due to an unenriched combustible mixture, early ignition, or a malfunction of the cooling system. Overheating is very dangerous for spark plugs, because it leads to cracks and various types of damage. Most often, this situation requires replacement.
Red and brown soot
As for red (sometimes called brown) soot, its appearance indicates the presence of unnecessary components in the fuel. It is also possible that too many additives have been added to the oil. A color like red brick may also appear if the engine has been running on leaded gasoline for a long time. The surface of the insulator is covered with a brown conductive coating, which disrupts the normal formation of sparks.
Fixing the problem is quite simple - clean the system.
The spark plug does not produce a spark if carbon deposits close the gap between the electrodes. This is a standard situation for cars in which the engine is subjected to high loads for a long time. To solve the problem, replace the spark plugs.
Black soot - what does it mean?
Black carbon deposits, often coupled with oily stains, are found quite often on both carburetor and injection types of engines. It indicates existing problems in the ignition and engine systems, depending on the type, but the exact cause of its occurrence can be determined after a detailed examination of various parts of the system.
In addition, black soot on a carburetor engine will differ from soot on an injection engine, but if the layer on the insulator is uniform, dry, and the color is closer to gray-brown, then perhaps there is no reason to panic, and the engine is operating normally, and candles gradually exhaust their resource.
The appearance of oily spots on the threads or electrodes is the first sign of oil getting into the combustion chamber. As a rule, thicker smoke with a bluish tint comes out of the exhaust pipe. This may happen due to:
- wear of valve seals or guide bushings;
- wear or sagging of valve piston rings.
If excess oil enters the combustion chamber, the problem lies in the parts of the cylinder-piston group. Perhaps the mobility of the piston rings is reduced, or they have become stuck, or the oil seals and guide bushings need to be replaced. In any case, black candles indicate the need for comprehensive engine diagnostics to determine the specific cause of excess oil.
If there are no oily spots, and a characteristic black soot of a “velvety” type forms on the candles, then most likely more gasoline enters the combustion chamber than necessary, which can also be determined by increased fuel consumption.
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In this case, there may be several reasons for the appearance of unwanted plaque:
- incorrect operation of the spark plugs, they do not have enough power to produce the required spark;
- compression in the cylinders is broken;
- problems in carburetor settings (for similar types of engine);
- the air filter is clogged;
- parts of the cylinder-piston group are worn out.
If such deposits are detected, the spark plugs must first be cleaned of carbon deposits or replaced. Next, it is recommended to check the compression in the cylinders, adjust the carburetor, check the fuel level in the carburetor chamber and the jets. On an injection engine, you need to diagnose the injectors, replace the air filter and check the settings and calibrations of the fuel maps, especially if the engine has been chip-tuned.
How does oil get into the spark plug well?
It’s very simple, in the hands of service station specialists or warranty service. It also happens that a part breaks through the thread. Especially when you often unscrew the spark plug, there is no 100% tightness.
After all, exhaust gases may still contain oil particles, and they end up in the well.
Valve cover seals can also leak; over time, they become tanned and begin to leak oil into the spark plug wells.
Just understand - half a drop is enough for it to then settle on the insulator with ionized air in the form of a brown coating.
This can also include dust, dirt, etc. All this also settles.
Of course, there are perfectly clean insulators even on 16 valve engines, but the point here is different
Light electrodes
White or light gray spark plugs in all cylinders are a sign of a lean air-fuel mixture supplied by the injector or carburetor. Moreover, the skirt, area near the electrodes and the threaded part are absolutely dry, without traces of oil.
Why is the fuel mixture supplied lean?
- lambda - the probe incorrectly informs the control unit about the amount of oxygen in the exhaust gases, the reason is sensor wear;
- faulty or clogged nozzles;
- incorrect carburetor settings or clogged fuel jets;
- insufficient pressure in the injector fuel rail;
- problems with the idle air control;
- air leakage under the manifold or in another place;
- unsuccessful chip tuning of the controller made by the owner of the car.
A lean mixture does not pose any particular danger to a running engine, but it does cause discomfort to the driver. The car accelerates slowly, pulls poorly and jerks - there is a lack of fuel. Oddly enough, the phenomenon causes increased gasoline consumption - a car enthusiast who wants to achieve better performance indicators presses the accelerator pedal harder and more often.
Note. Often the light shade of the working electrodes is explained by the type of fuel used. If the car is operated on methane or liquefied gas (propane-butane mixture), this color is considered normal.
The working part is covered with black soot
Black spark plugs are a symptom indicating that the fuel mixture is too rich (the proportion of gasoline is increased above normal). Therefore, the fuel does not burn completely and forms a layer of soot on the chamber walls and spark plug electrodes.
An additional sign of this problem is black or dark gray smoke from the exhaust. When over-gassing, small flakes of soot may fly out of the pipe.
There are quite a few reasons for the enrichment of the air-fuel mixture, the most common ones look like this:
- One of the key sensors has become unusable - air flow, temperature, throttle position or oxygen content in the exhaust (lambda probe). The controller activates the emergency program and prepares the mixture according to other indications.
- Carburetor malfunctions (clogged air jets, worn throttle valves, etc.).
- Failure of the pressure regulator in the fuel line.
- Wear of nozzles - nozzles “overflow” and leak when the power unit is not working.
- Problems with sparking - the power of the electrical pulse is not enough to ignite the combustible mixture normally.
Important! If during the diagnostic process you find black spark plugs, the fault should be found immediately. Increased gasoline consumption is only part of the consequences of excessive enrichment.
There are others, not so harmless:
- some of the unburned fuel penetrates the crankcase and dilutes the oil, accelerating the wear of engine parts;
- the other part gets into the exhaust manifold, which is why shots are periodically heard in it;
- soot clogs the expensive catalytic converter - it has to be cleaned or replaced with a new one;
- The service life of the spark plugs is sharply reduced.
When running on a rich fuel mixture, the engine “chokes”, unstable idling and skipped cycles are observed. When a certain amount of soot heated to a high temperature accumulates in the chambers, a “pseudo-diesel” effect occurs - after turning off the ignition, the engine does not want to stall and makes 2-10 crankshaft revolutions. The reason is hot soot, igniting the combustible mixture without a spark.
Traces of technical fluids on spark plugs
Traces of gasoline are the result of a non-functioning or intermittently functioning spark plug. In this case, a spark does not occur in the cylinder and the fuel simply does not burn, but flies out into the pipe, and also settles on the elements installed in the combustion chamber, including the spark plug.
Strongly visible traces of oil on the electrodes of the spark plugs are the result of excessive amounts of lubricant entering the combustion chambers. This happens in case of severe wear of the cylinder-piston group or oil seals and valve guides. Because of this, oil penetrates into the combustion chamber in unacceptable quantities.
Cleaning spark plugs - using proven methods
Timely cleaning of spark plugs allows you to extend their life and stabilize the operation of the ignition system and the engine as a whole. Several methods can be used to clean carbon deposits. The simplest and most convenient is cleaning at home using fine-grained sandpaper or a metal, nylon or even toothbrush. Carefully clean the contaminated surface with a brush, then sand with fine sandpaper. The most important thing is to try not to deeply scratch the surface and not to disturb the established gap between the electrodes, so do not use rough objects (screwdrivers, awls) for cleaning.
The second way to wash off the deposits that have formed is to use available household chemicals and various detergent compositions. Degrease the contaminated surface, then dip the candles in a solution with detergent and leave them for several hours; acetone, vinegar, and household chemicals are well suited for these purposes. To cleanse yellowish or red plaque, you can even use affordable products such as Cola or Sprite. They contain orthophosphoric acid, which facilitates easy cleansing. When using ammonium acetate or another acidic solution, you must first calcinate the candles and heat them to a high temperature, and then sharply lower them into the acid solution for several minutes.
High-quality cleaning of spark plugs can also be carried out in specialized car services. As a rule, they offer cleaning with special ultrasound or sandblasting.
