The situation when fills a candle on a trimmer, is familiar to every owner of a gasoline tool, be it a Chinese “no name” or a famous Stihl. Instead of starting the engine vigorously, you get a wet electrode, the smell of gasoline and a complete lack of spark. This is a classic sign of a mixture formation disorder when an excess amount of fuel enters the cylinder or the ignition system is malfunctioning.
Why does this happen after a long period of inactivity or an attempt to start it “cold”? Most often, the culprit is an incorrect sequence of actions during startup or incorrect settings. carburetor. Gasoline, without having time to evaporate, condenses on the electrodes, creating a conductive film that blocks the discharge. If you ignore this symptom and continue to pull the starter, you can “kill” the coil or completely clog the cylinder.
In this article we will analyze in detail the mechanics of the process, check the status fuel mixture and learn how to properly dry the combustion chamber. You don't need to be a professional mechanic to fix this problem yourself using a minimal set of tools.
Mechanics of the process: why gasoline stops burning
To understand the root of the problem, it is necessary to consider how it works two stroke engine trimmer. The mixture of gasoline and oil enters the crankcase, then into the cylinder, where it is compressed by the piston and ignited by a spark. If at this moment the spark is weak or absent at all, unburned fuel settles on the walls and, of course, on the spark plug. Candle bay - this is always a consequence of an imbalance between the air and fuel supply.
Users often forget that a cold engine requires a rich mixture to start, but an excess of this mixture is destructive. When you repeatedly pull the starter with the choke closed, pure gasoline is pumped into the cylinder, which washes away the oil film and gets wet insulator. At this moment, the engine “chokes” and stalls, and restarting becomes impossible without drying out.
It is also worth considering the quality of the components. Cheap spark plugs with a large gap or low heat rating may not have time to self-clean from carbon deposits, which leads to regular failures. If a thick layer of black carbon deposits has formed on the electrode, the spark will strike along the shortest path - through the carbon deposits onto the body, and not into the gap.
Diagnostics of the condition of the spark plug and ignition system
The first step should always be a visual inspection. Unscrew the spark plug and inspect it carefully. The color and condition of the electrodes will tell you more about the “health” of the engine than any diagnostics. If the electrode is dry and has a light brown or grayish tint, the system is working normally, and the problem may be a lack of spark due to a faulty coil.
If you see black, oily soot or drops of liquid fuel, this is direct confirmation that carburetor prepares mixture too rich. A wet, black candle indicates over-enrichment, and a dry white one indicates overheating or running on a lean mixture, which is also dangerous, but for different reasons.
⚠️ Attention: If upon inspection you find that the electrode is completely destroyed or melted, do not under any circumstances attempt to clean it or adjust the gap. Such a spark plug requires immediate replacement, since a piece of metal that falls off can jam the piston.
Checking the spark is carried out by applying the threaded part of the spark plug to a metal part of the engine (ground). When the starter is cranked, a bright blue spark should jump between the electrodes. If the spark is red, weak or absent, the problem lies with the ignition module or wiring, not the fuel itself.
Main causes of rich mixture and flooding
Why does so much gasoline get into the cylinder? The most common culprit is improper launch preparation. Many users, especially in cold weather, forget to open the choke after the engine first fires up. The engine starts to run rough, consumes a huge amount of fuel and stalls, leaving the spark plug wet.
The second common reason is poor quality fuel mixture. If you use old gasoline that has been sitting in a can for more than a month, or if you mix the oil with gasoline incorrectly (too much oil), combustion will be disrupted. Excess oil in the mixture leads to coking of the piston rings and spark plugs.
The third reason is mechanical malfunctions of the carburetor. The valve needle may lose its seal due to debris or wear, causing fuel to continue to flow into the chamber even when the engine is turned off. This leads to the fact that the trimmer may not start even after a long period of inactivity.
- 🛠️ Clogged air filter: if the filter is clogged with dust or grass, little air enters the cylinder, and the mixture becomes over-enriched.
- ⚙️ Broken carburetor settings: The mixture quality screw (L) is turned too far, supplying excess fuel at low speeds.
- 🌡️ Low compression: wear of the piston group prevents the creation of sufficient vacuum for proper suction of the mixture.
Algorithm of actions: how to dry a flooded candle
If the candle is already wet, simply wiping it with a rag is not enough. The gasoline remains in the cylinder, and the new spark will drown in the fuel again. It is necessary to complete the procedure for completely drying the combustion chamber. To do this, unscrew the spark plug and wipe it thoroughly with a rag, removing all carbon deposits and remaining oil.
While the spark plug is drying, it is necessary to remove excess fuel from the cylinder. Insert a clean rag into the spark plug hole and pull the starter sharply several times. This will throw the remaining gasoline out. Do not be afraid that the engine will “seize” without a spark plug - at this moment it only expels excess fluid.
After the chamber is purged, let the candle dry completely or heat it (carefully!) over a gas burner if you are sure of its integrity. Reassemble everything, but do not install the air filter yet to ensure maximum air flow for the first start.
☑️ Engine drying checklist
When assembling, make sure that the spark plug is screwed in all the way by hand, and then pressed with a wrench. Do not overtighten the threads, as the cylinder head is usually aluminum and can be easily damaged. After starting, allow the engine to warm up at idle speed before applying load.
Carburetor adjustment and filter check
If drying helped only temporarily, and after a few minutes of operation the trimmer stalls again or the spark plug begins to “throw”, adjustment is required carburetor. Most trimmers have three adjustment screws: L (low speed), H (high speed) and T (idle).
Adjustment should begin with the screw L. Screw it in smoothly until the engine starts to run rough, then back it out half a turn. This will lean the mixture at low speeds, which often solves the problem of flooding at startup. Screw H It is better not to touch it without a tachometer, as its incorrect setting can lead to overheating and scuffing of the piston.
Don't forget about the air filter. Remove the cover and assess the condition of the filter element. If it is soaked in oil or clogged with fine grass dust, the engine will suffocate. Wash the filter in soapy water (if it is synthetic) or replace it with a new one.
| Symptom | Probable Cause | Action |
|---|---|---|
| The spark plug is wet, there is a spark | Overrich mixture | Blow out the cylinder, adjust screw L |
| The spark plug is dry, no spark | Coil fault | Replace the ignition module |
| Candle in black soot | Lots of oil in the mixture | Drain the fuel and make a new mixture |
| Trimmer stalls on gas | Fuel filter clogged | Replace the filter in the tank |
Prevention: how to avoid problems in the future
So that the question “why the spark plug on the trimmer is flooded” no longer bothers you, it is important to follow the operating rules. The main rule: do not store the trimmer with a full tank and the engine running. Before long-term storage (more than 2 weeks), drain the remaining fuel from the carburetor by allowing the engine to stall itself.
Use only fresh fuel. Gasoline with ethanol tends to stratify and absorb moisture from the air, which leads to the formation of condensation in the tank. Water is heavier than gasoline and enters the carburetor first, causing corrosion and disruption of mixture formation.
Regularly clean the cylinder cooling fins of grass and dust. Overheating the engine leads to detonation and the formation of carbon deposits, which reduces sparking efficiency. A clean engine is the key to stable operation and easy starting in any season.
Monitor the condition of the fuel hose inside the tank. Over time, it can crack, and air will be sucked into the system, interfering with the carburetor. A visual inspection of the hose once a season will help avoid sudden breakdowns in the midst of work.
Frequently asked questions and answers (FAQ)
Can I use a car spark plug in a trimmer?
Absolutely not. Car spark plugs have a different heat rating and design. In a two-stroke trimmer engine, they will quickly become covered with soot, as they will not be able to self-clean at high temperatures and in an oily environment, which will lead to engine failure.
What gap should be on the trimmer spark plug?
The optimal clearance for most chainsaws and trimmers is 0.6 to 0.7 mm. Too large a gap requires a high voltage for breakdown, which the coil may not provide, and too small will produce a weak spark, insufficient to ignite the mixture.
Why does the trimmer start and immediately stall?
Most often, this is a sign that the muffler mesh or fuel filter in the tank is clogged. The engine does not have enough fuel at high speeds or it “chokes” from exhaust gases. The reason may also be air leaks through the crankshaft seals.
How often should you change the spark plug on your trimmer?
The life of the spark plug depends on the quality of the fuel and the load. On average, with active use, it is recommended to change the spark plug once a season or after 100 engine hours. However, if it is visually intact and produces a good spark, replacement may not be necessary.