12 reasons why black carbon appears on candles and how to eliminate it

What does the color of carbon deposits on spark plugs indicate?

In older cars, it was normal practice to bake out the spark plugs. What did it mean? The user unscrewed them and calcined them over a fire with a burner to burn off the resulting deposit of hydrocarbons. It was enough to hold it for a few minutes, and then let it cool and clean it mechanically, without disturbing the gap and integrity of the parts. This was normal, but how could such signs be normal for a modern car? The color of the spark plugs is actually of great importance and will tell an experienced driver about the presence of defects. Black soot of different shades may indicate to an experienced craftsman the following signs:

• poor quality of fuels and lubricants;
• poor fit of the rings to the cylinder walls;
• poor quality or wear of the spark plugs themselves.

A beginner will understand the harm and be able to distinguish the difference, but everyone will see that it is wet or dry. What this means is a separate question, because there can be several reasons. White soot also does not bring anything good and has its own reasons.

Types of soot

Yes, indeed, black carbon deposits on spark plugs mean a lot. This is especially true for domestic cars VAZ 2109, 2114 and other brands. To deal with the consequences, it is necessary to study all the states of the spark plugs in which they are in the engine. So, a candle has the following symptoms:

• Completely dry and no traces of soot - this condition indicates the absence of any problems with the internal combustion engine or they were just recently screwed in and have not expired to determine the condition.
• Wet - a problem with the carburetor, which pours an excessive amount of fuel into the cylinder.
• Dry, friable - long-term operation on an enriched fuel mixture, incomplete removal of exhaust gases from the cylinders.
• Oily black – the color of the soot has its own problem. But it is important to consider not only color, but also structure. Oil should not penetrate the cylinders at all.

Each state of the candle speaks volumes. This applies to absolutely all cars, it’s just more pronounced in older ones due to their service life. Old spark plugs must be replaced promptly.

Which color is not dangerous?

The performance of a gasoline engine directly depends on the condition of the spark plug electrodes. Their surface should be painted in a dirty brown shade, without traces of oil and soot elements.

If the surface of the spark plug is changed, it is recommended to carry out unscheduled technical diagnostics to detect the cause of such problems. Various parts of a gasoline engine can provoke such changes.

There are several color options that cover spark electrodes. These include:

• Grey;
• White;
• Terracotta;
• Red;
• Black.

The top of the spark plug may be covered with various deposits. Most often it is subject to oil deposits or a thick layer of soot. Such changes indicate serious problems with the engine.

Causes of black carbon deposits on spark plugs

Does your car have one black spark plug or are they covered in soot and oil all over? Don't hesitate because there is a growing problem in your car's engine that could cause more serious damage. The color condition of this spare part speaks volumes, so it is recommended to contact experienced service professionals. Unfortunately, there are many reasons why soot appears on candles. Let's look at them in more detail, indicating more precise signs of the defect.

The ideal condition of the engine is a dry spark plug, if, of course, the part was installed a long time ago and the car worked on it a fair amount. There should be dryness on all cylinders, which can also be one of the diagnostic methods. Sometimes, before selling a car, former owners install new spark plugs to cover up problems. But even in a short time, some traces will definitely appear on them.

If the candle turns black quickly, literally within a few trips, then you should sound the alarm. The engine develops a problem that may become critical. Carbon deposits can appear due to a breakdown in the power unit, in particular, wear of the piston pair, incorrect ignition angle setting, incorrect operation of the fuel system, and much more. It is important not to get confused, because a spark plug can turn black for completely different reasons, and the wrong direction during repairs can cause additional problems. Black carbon deposits need to be treated correctly. Considering engine failures exclusively, the reasons may be as follows:

• valve burnout;
• mismatch in heat rating;
• incorrect ignition angle;
• highly enriched fuel mixture;
• clogged air filter;
• increased pressure in the fuel rail;
• low compression;
• insufficient self-cleaning;
• inconsistency of fuel quality;
• defects in the spark plug itself.

Black spark plugs. Cause: valve burnout

Each engine cylinder is equipped with intake and exhaust valves. During operation, a huge temperature is created inside, comparable to the melting point of the metal. This leads to related problems. For example, a valve burnout occurs. Spark plugs become covered with a black coating due to burnout of the valves, but why does it occur, strictly speaking? To fix the problem, you need to dig deeper and find out why the spark plug on the injector turned black and why the valve burned out? In such a situation, a diagnosis is carried out, and an experienced technician determines one of the following root causes:

• valves are pinched;
• the guide bushing is worn;
• valve stem is damaged.

Also, sooty spark plugs may be due to running on a very lean mixture. This defect especially manifests itself on machines on which gas-cylinder equipment is installed. The specific cause is determined through detailed disassembly and diagnostics.

Spark plugs - black soot due to mismatch in heat rating

A candle is not an ideal product that has the same characteristics. Manufacturers make them differently, and one of the characteristics is the heat rating. It reflects the period of time during which the spark plug completely switches to glow ignition, that is, a spark is practically no longer needed to ignite the fuel. It is ignited by heated candles. Accordingly, the longer this time interval, the longer you need to act on it to heat it red-hot. If your car is equipped with spark plugs with a low heat rating, they will warm up quickly and the operating mode of the internal combustion engine will be disrupted. When will the driver notice this problem? Not right away, because at low power the motor works fine. As speed increases and temperature rises, power drops and fuel is wasted.

Why do spark plugs turn black when ignition is late?

To determine late ignition as the main cause of blackening of the spark plug, it is necessary to observe them. A black coating will gradually form on them and intensify. Late ignition will disrupt the operation of the internal combustion engine. This will not only be visible on the candles, but will also be felt by ear. The engine begins to vibrate slightly as the gases inside the cylinder do not have time to escape and hit the exhaust valve. The ignition must be adjusted so that the fuel has time to ignite, burn to release the required energy and be pushed out through the valve. For this, a hall sensor is used and a complex control unit is installed. The injection and ignition systems are synchronized to ensure maximum efficiency.

Rich air/fuel mixture

The engine of a modern car has very fine tuning. All processes must be perfectly tuned in it so that maximum power is provided to the shaft throughout the entire operating cycle. This also applies to the degree of fuel enrichment with oxygen. The optimal ratio of oxygen to fuel is 15:1, that is, 15 volumes of air are used and only 1 volume of gasoline. If this concentration changes, the amount of fuel increases, then the mixture becomes rich. When it burns, more soot and soot are formed in the cylinder, which is why the spark plugs are black. The increased amount of combustion products does not have time to leave the volume and does not burn out completely, settling on the walls of the parts.

Clogged air filter

For normal operation of an internal combustion engine, a lot of oxygen is required. As stated earlier, only 1/15th of the fuel volume is needed to obtain the optimal ratio. This balance can be upset in two ways: give more fuel or let less air into the engine. The second is more likely, since the air filter becomes the only obstacle to the air flow. Black soot is formed as a result of disruption of the fuel combustion cycle, and is formed from unburned products in the form of soot.

Problems with the ignition system

The internal combustion engine should be considered like a Swiss watch. All processes must be perfectly tuned to ensure maximum power and endurance under load. The basic or primary setting of the ignition time of the fuel mixture in the cylinders is performed by the car manufacturer. During operation, this happens automatically, due to a system of sensors and algorithms debugged by specialists. For example, ignition that is too late may well cause the formation of a black deposit, since all the fuel does not have time to burn and flies out alive into the exhaust manifold.

Excessive pressure in the fuel rail

The fuel rail is a pressure regulator for the flow of flammable liquid, which is then directed to the injectors for injection. The efficiency of the internal combustion engine and the condition of its parts directly depend on it. The RDP supplies fuel to the atomizers in a dosed manner, but the device settings can be changed. This is done to ensure maximum power of the power unit. The control limit is small, since the slightest changes already lead to a significant change in the operating cycle. Simultaneously with the formation of carbon deposits on the spark plugs, unstable engine operation also occurs, increases fuel consumption, slow response to the gas pedal, and lack of acceleration.

There is black soot on the spark plugs due to poor self-cleaning.

To ensure that the motor runs for a long time and smoothly, the manufacturer came up with a special mode - self-cleaning. This is a procedure in which the temperature in the cylinders rises to high values. The candles heat up to 400 degrees. All hydrocarbon deposits formed on them spontaneously burn. For various reasons, this operating mode may be disrupted, which leads to insufficient cleaning of the spark plugs. Almost any car can be switched to this mode. To do this, it is enough to accelerate to maximum speed, but it is safer to give the gas in a lower gear so that the speed remains at least 5 thousand.

Why is the spark plug black when compression is lost?

Another cause of black deposits on spark plugs is low or insufficient compression. This defect manifests itself in several signs:

1. Reduced power because the cylinder is not sealed and the pressure is released into the cavity rather than used to rotate the piston.
2. Oil deposits and black soot form on the candles, because when the oil burns, a lot of products are released, which settle on the walls.
3. The quality of the exhaust deteriorates and the car begins to “smoke” in the literal sense of the word.

Why is the spark plug black due to unsuitable gasoline?

Gasoline and gasoline are different. This type of fuel varies depending on the initial quality of the oil. But as a result of sublimation, it must fully comply with the standards. Therefore, there are two main reasons for the decrease in its quality: violation of production technology and dilution after sublimation. The higher the octane number, the better and at a higher temperature the gasoline burns. When it is diluted, the efficiency decreases, but the amount of combustion products that remain on the walls in the form of soot increases.

Why is there a black candle on the walk-behind tractor?

There is a technique in which the spark plugs are black and this is considered a normal condition. Of course, it’s not entirely correct, but it solves a lot of other problems. Sacrificing the service life of the piston and spark plugs, manufacturers simplified the design. As you know, a small engine does not have a cooling and lubrication system. It is supplied to the cylinder along with fuel, which makes the units more mobile and compact. In order for walk-behind tractors to work properly, you need to periodically clean the spark plugs from deposits.

Spark plug defects

Only problems in the internal combustion engine should not be considered as the cause of blackening of spark plugs. This phenomenon can also occur due to the presence of a defect in the candles themselves. It is a device consisting of several elements. If production technology is not followed or worn-out ones are used, various defects may appear.

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.

What to do if a black plaque appears

The presence of black deposits on the spark plugs is not a normal condition of the part. It is necessarily associated with some problem in the internal combustion engine, fuel system or ignition. It is necessary to respond quickly to prevent the problem from becoming more serious. The first step is to find out why the candles turn black and eliminate the root cause. If the spare part is still normal, then clean it from carbon deposits. You can use special tools or use the old-fashioned proven method - calcination with a burner.

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.

The best prices and conditions for the purchase of new cars

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.

How to remove black carbon deposits from ignition elements

If black deposits have formed on the spark plugs and in the cylinder, it is not so easy to remove. Still, there are several ways: chemical and mechanical. Both have their pros and cons. Let's take a closer look at each.

Mechanical cleaning method

This method consists of washing the oil, if any, in gasoline. Then the candle is dried and all carbon deposits are removed using sandpaper. It is important to monitor the size of the gap between the electrodes so as not to break it. The efficiency of ignition of the fuel mixture will depend on this. You should be careful, as you can break off the central electrode.

Chemical cleaning method

This method of removing black deposits from spark plugs involves using chemicals. It is highly not recommended to add additives to the internal combustion engine or fuel, even if sellers advise it. There will be more problems from them later. You need to unscrew the spark plugs and wash them in gasoline. Then take the ammonium acetate solution and heat it to 90 degrees along with the candles. For the reaction to react, it is recommended to keep them in the solution for at least 30 minutes. At the end of the procedure, you need to dry and wipe the candles dry. All the carbon deposits will be removed as if by hand.

Repair recommendations

Regarding repairs, we will consider each case individually, since individual faults and types of soot indicate the need for different types of repair work .

Oily black soot

The appearance of oil deposits indicates the penetration of oil into the combustion chamber. Accordingly, it is necessary to thoroughly study the condition of all components that could cause such a defect, and, if necessary, replace them. These components are :

Guide bushing wear

Wear of valve stem seals

The problem relates strictly to the wear of components of the cylinder-piston system. Accordingly, they must be replaced.

Dry black carbon

Regarding the second type, there are several more reasons than in the case of oil deposits . And it is impossible to clearly understand which one is causing the soot without checking each one.

The first, easiest to check is a faulty spark plug, or lack of energy in it, the solution to the problem is to replace the spark plug.

Changing the spark plug

We measure the compression in each cylinder

Adjusting the fuel pressure

Cleaning the air filter

Checking for errors

Air leak

A lean mixture can also form due to the leakage of foreign air. If you cannot find the cause of the white spark plugs, and all checks have shown that the components and elements are in good condition, then it is recommended to carefully inspect each hose and pipe leading from the air filter to the intake manifold.

In addition, there may be air leaks where the idle speed sensor is installed. Experts recommend carefully checking the rubber seals that seal the connection.

Source

Adjustment procedure

Proper engine operation depends on compliance with operating rules and strict compliance with technical inspection requirements. Before you start setting up the carburetor on the Alpha moped, you need to first carry out a number of works:

1. Clean the carburetor body.
2. Replace the spark plug.
3. Replace the air filter.
4. Make sure the connections are tight.

Now you need to accurately set the gasoline level in the float chamber by bending the float tongue. By connecting a transparent hose to the drain fitting, it is possible to determine the absolute fuel level. To do this, the hose is lifted up. Typically the height is at the junction of the carburetor caps.

The next step is to adjust the idle speed system using quantity and quality screws. The whole process takes place on a warm engine. The quality screw is screwed in until it stops and then unscrewed two turns. Start the engine and, by rotating this screw in both directions, achieve maximum speed. Then use the quantity screw to reduce the speed to the minimum stable speed. It is possible that the procedure may need to be repeated several times until the desired result is achieved.

Adjustment of the middle speed range occurs by raising or lowering the needle. To do this, you need to unscrew the throttle nut, remove the needle and move the corkscrew into one of the grooves: above the middle division to lean the mixture and below to enrich it.