The situation when the engine refuses to start immediately after the decoking procedure causes panic in most motorists. You spent time and money on chemical cleaning of the piston group, counting on improving dynamics and reducing oil consumption, but got the opposite effect. Instead of a confident start - a deaf silence or convulsive attempts of the starter to turn the crankshaft. This is a common problem with specific technical reasons and is usually solved without serious interference with the design of the motor.
The main difficulty is that the aggressive chemical compositions used to dissolve the soda change the physicochemical properties of the medium inside the cylinders. The liquid can penetrate into places where it should not get into normal operation mode, or create conditions that prevent normal spark formation. Understanding the physics of the process will help you act in cool blood and avoid making mistakes that can really lead to a major overhaul.
In this article, we will discuss the mechanical and electrical causes of failure to start, the algorithm of actions for resuscitation of the engine and prevention methods. You'll find out why. hydraulic impact The main enemy in this procedure is how to properly prepare the car for the first start after a chemical attack. It is important not to make sudden movements and follow a clear diagnostic plan.
Reasons for failure of the launch: chemistry and mechanics
The first thing to realize: decoking is not just a flushing, it is the aggressive effect of alkalis or solvents on coking rings. If the machine does not start after the procedure, in 80% of cases the liquid itself is to blame, which did not have time to evaporate or was removed from the cylinders. The residues of the composition on the electrodes of spark plugs create a conductive bridge or, conversely, a dielectric film that blocks the spark. Flooded candles The most common but common reason for failure.
And the bigger problem is, hydrostroke Or micro-hydro-impact. If you poured too much decoxting fluid and did not control its level, the piston at the compression stroke rested on the incompressible liquid. This could have caused the rod to deform or even cracked the cylinder block. In mild cases, the motor simply cannot turn because of the resistance of the liquid in the combustion chamber. The starter is spinning, but the crankshaft is dead or moves in jerks with a characteristic sound.
It is also worth considering the state of piston-ring. If the coar was the only factor keeping the rings in the working position (which happens on very worn-out engines), then after its dissolution, the rings could "lay down" or lose contact with the cylinder walls. As a result, the compression falls to the critical values necessary to ignite the mixture. The engine rotates easily, "as empty", but does not catch.
⚠️ Warning: If you hear a strong metal thud, crunching or squealing when you try to launch, stop trying immediately! Continued rotation of the starter can turn the oblique rod into a pierced block of cylinders. In such cases, a complete defect of the engine is required.
Another hidden cause may be damage. sensor Or wires. Aggressive solvent vapors could oxidize contacts or damage the insulation of high-voltage wires if they were old-style. In addition, the introduction of chemistry on the belt of the timing (in some engine designs) can lead to its slippage, although this is less common. It is important to check the integrity of all visible elements of the hood space.
Diagnostics of the ignition system and candles
To begin the search for malfunction should be with the simplest and most affordable element - the ignition system. Since decoking involves twisting candles for pouring the composition, this is where the error most often lies. Even if you thoroughly wiped the candles before installation, microscopic residues of liquid or vapor could remain on the insulator or electrodes. Spark failure It's impossible under these conditions.
The algorithm of actions should be as follows. Remove high-voltage wires or ignition coils. Turn all the candles and examine them carefully. If they are wet, smell of solvent or have a black coating, they must be cleaned. The ideal option is to blow out the cylinders and dry the candles outdoors or heat them up with a safe source of heat (not open fire!).
Checking the spark "on the mass" is a mandatory stage. Tie the candle to the engine body (or use a special tester) and ask the assistant to spin the starter. The spark should be bright, blue and stable. If there is no spark, the problem may be in the coils, which may also have been affected by chemistry or moisture. In modern engines with individual coils (coil-on-plug) is more likely to fail one of them.
- 🔌 Visual examination: Check the candles for cracks insulator and soot, make sure the electrodes are dry.
- ⚡ Spark test: Make sure that the high-voltage discharge breaks the gap and has a rich blue color.
- 💧 Humidity control: Wipe candle wells with dry rags to exclude moisture from the contacts of the coils.
- 🔋 AKB charge: Make sure the battery is charged, as a long scrolling starter could land the battery.
If the candles are dry, but there is a spark, and the engine does not start, then the problem is not in the ignition system. Perhaps the process of mixing is disrupted or the engine itself is mechanically damaged. Do not rush to put new candles until you are sure of the serviceability of the old ones or the absence of traces of chemistry on them.
Use a technical dryer or compressed air to dry the candle wells and candles themselves quickly. Residues of moisture with solvent can evaporate for a long time naturally.
The problem of hydraulic shock and excess liquid in the cylinders
The most dangerous scenario is when there is liquid in the cylinders. As mentioned earlier, decoking formulations often have an oily base or contain aggressive solvents that do not evaporate instantly. If you poured them “to the top” and left them overnight, some of the liquid could leak through the rings into the crankcase, and some could stay in the cylinder. When trying to start the piston meets the resistance of incompressible liquid.
To exclude hydraulic shock, it is necessary to forcibly remove the remaining liquid from the cylinders. For this, the candles are twisted, and the engine is scrolled by the starter. In this case, fountains of chemistry can fly out of the candle holes. It's important.: be sure to cover the holes with dense rags or cardboard with slots, so as not to splash the entire underhood space and yourself. The liquid will fly out under compression pressure.
After the procedure of "spitting out" the liquid, it is necessary to give the engine "breathe". Leave the candles twisted for 15-30 minutes so that the solvent vapors evaporate. At this time, you can check the level of oil in the engine. If the decoking was successful and the rings were coked, some of the fluid could get into the crankcase and the oil level could rise. This is dangerous, as the oil loses its properties and can foam.
| Symptoms. | Probable cause | Action. |
|---|---|---|
| Starter's not spinning, wedge | Hydroshock (liquid in cylinder) | Twisting candles, scrolling with a starter |
| Starter is easy, doesn't start. | No compression or candles flooded | Compression measurement, candle drying |
| He's grasping, but he's deaf. | Chemistry in the inlet/sensors | Blowing, cleaning throttle, resetting errors |
| Strange sound when scrolling | Mechanical damage (shutun) | Diagnosis for SRT, defects |
⚠️ Warning: Never try to start an engine if you suspect there is a lot of liquid in the cylinders! This is guaranteed to lead to deformation of the rods. First, remove the liquid through the candle holes.
If after removing the liquid and drying the engine still does not start, but spins freely, proceed to the measurement of compression. The absence of compression will indicate that the rings after cleaning did not press against the walls or, conversely, stuck in the grooves due to the lack of a sealant.
☑️ Post-coking check
Starting the engine: step-by-step instructions
When the preparatory stages are passed, the candles are dried or replaced with new ones, and the cylinders are freed from excess liquid, you can start the first run. This moment requires care. Do not immediately gas or keep the key in the “start” position for a long time. The algorithm should be gentle for the “woke up” engine.
First, connect a fully charged battery. A weak charge may not give enough rotation frequency of the crankshaft to create the desired thinning and spark. Turn on the ignition for 5-10 seconds, so that the gas pump pump pump pumps pressure into the ramp, and the ECU conducted a survey of the sensors. If the check engine is on fire, that’s okay.
Attempt to launch in short series of 3-5 seconds. If the engine “captures” but stalls, try to slightly give the gas (if the throttle is mechanical) or just try again. On modern cars with electronic throttle (Drive-by-wire) the pedals are better not to touch - the computer will set the necessary turns for warming up and purging. After successful start-up, the engine can work unstable, triple or smoke - this burns out the remains of the decoxer.
Procedure for the first launch:1. Connect the charged battery.
2. Activate ignition (10 sec).
3. Starter for 3-5 seconds.
4. When grasping - do not gas sharply.
5. Give me 2-3 minutes to work for singles.
Watch the color of the exhaust. Thick white smoke with a pungent smell is normal in the first 10-20 minutes of work. If the smoke is black (oil) or gray, and it does not go away after warming up, it may not have helped, or oil caps have been laid. If the engine is running smoothly, let it warm up to operating temperature, then shut off and check the oil level again.
The first start after decoking should take place at minimum speeds. Avoid high loads for the first 50-100 km of run until the rings finally take their places.
Mechanical consequences and ring occurrence
It happens that the decoding was technically correct, but the result was deplorable due to the physical condition of the engine. The grooves of piston rings sometimes served as a sealant. When the chemistry dissolved this char, the rings lost their elasticity or, conversely, “released” and went deeper into the groove, no longer contacting the cylinder wall. The compression in this case falls to 2-4 atmospheres, which is not enough for ignition.
This can only be diagnosed by measuring compression. If all cylinders it is low and the same – the engine is worn out, and the decoking only revealed the problem. If the low is only in one cylinder, it is possible that a bully formed there or the ring burst. In some cases, “dynamic” decoking helps: pouring a small amount of special oil into the cylinders and short-term engine operation, which can help the rings stir.
However, if the compression is absent completely, and when scrolling, a whistling or hissing is heard (air output into the intake or release), then the valves are not sealed or the piston is burned. The chemistry could cause the detachment of large pieces of soda, which, flying through the valves, damaged their edges. This requires removing the cylinder head (HBC) and repairs.
- 📉 Low compression: Indicates wear of the rings or damage to the cylinder piston group (CPG).
- 🔊 Extraneous sounds: Knocking or hissing indicates mechanical damage or leaky valves.
- 🛢️ Oily charcoal: If after starting the oil consumption remained high, the oil caps are not elastic and require replacement.
It is important to understand that decoking is a preventive measure for engines with low mileage or the first signs of occurrence. For engines with mileages over 200-250 thousand km, where the gaps are already large, chemistry can become the “last nail” that finally achieved compression.
Can the engine be saved if the compression is lost?
In some cases, engine washing with high detergent oil and short-term operation in a gentle mode helps. There are also "repair" additives in the oil, temporarily increasing compression, but this measure is temporary. If the rings lie dead or burst - only disassembly and repair.
Prevention and the correct choice of means
To avoid the situation “does not start after decoking”, you need to choose the right tool and follow the technology. Cheap kerosene and acetone-based formulations can be too aggressive for rubber seals and oil caps, causing them to swell or break. Modern synthetic decoxing acts softer, but takes longer to react.
Always read the instructions for a specific product. Some products require a mandatory change of oil and filter immediately after the procedure, others allow you to travel another 500 km. Ignoring these requirements leads to the fact that aggressive chemistry remains in the lubrication system and destroys the crankshaft liners or hydrocompensators.
Before the procedure, be sure to warm up the engine to operating temperature. Cold motor and cold chemistry are the absence of reaction. It is also critical to control the amount of liquid that is poured. It is better to pour less and repeat the procedure than create a hydraulic shock. Use a syringe for the exact dosage in each cylinder.
⚠️ Note: Do not decoding on an engine with a faulty ignition system or trifle. Fix the basic problems first, or you’ll just fill the cylinders with fuel and chemicals, making things worse.
Competent approach to maintenance allows you to extend the life of the engine without expensive repairs. But if after all the manipulations the car does not start, do not continue the experiments. Call a tow truck and deliver the car to the service station for professional diagnosis. Savings on the tow truck can cost the cost of a new engine.
How long do you need to dry candles after cleaning?
The minimum time for natural drying is 30-60 minutes. However, it is best to blow the cylinders with compressed air and warm the candles with a hairdryer. If the candles are wet to the touch, you can not start the engine.
Can I turn the engine with a starter with twisted candles?
This is necessary to remove the remaining fluid. But do not twist for more than 10-15 seconds in a row, so as not to overheat the starter. Let him cool down for 2-3 minutes between tries.
What if a knock appeared after the decoding?
Shut down the engine immediately. Knock indicates mechanical damage (shaft, piston, liner). Operation is prohibited, diagnostics by hearing and measurement of oil pressure are required.
Do I need to change the oil immediately after the scaling?
Yes, in 99% of cases, the oil should be changed immediately, as dissolved soda and the chemistry itself get into it, which dramatically reduces the lubricating properties. It is also necessary to replace the oil filter.