The situation where the chainsaw Stihl MS 180 Refusing to stop after releasing the trigger of gas or switching the switch to the position "Stop", is not only annoying, but also potentially dangerous. The internal combustion engine continues to run at high revs, ignoring the operator's commands, which can result in serious injury or damage to the tool itself. The owner at this point is faced with a dilemma: try to block the fuel channel manually or look for the cause of the failure until the engine stalls itself from a lack of fuel.
The main reason for this behavior lies in violation of the tightness of the fuel system or mechanical jamming of the controls. Most often, the problem lies in the sucking of excess air through the crankshaft or gaskets, because of which the fuel mixture becomes too poor, and the engine cannot stop in a normal way. Also, it is impossible to exclude the possibility that the button “Stop” failed or oxidized contacts that break the ignition circuit.
In this guide, we will analyze in detail the fault search algorithm, paying special attention to the nodes responsible for fuel supply and spark formation. You will learn how to properly diagnose the condition carburettorCheck the integrity of the sealing rings and adjust the throttle. Understanding the principles of the two-stroke engine will help you quickly eliminate the defect and return the tool to work without contacting the service center.
Principle of operation of the engine stop system
To understand why. chainsaw Stile 180 does not respond to the switch off button, it is necessary to clearly represent the engine stop mechanism. Unlike four-stroke motors, there is no electric starter or sophisticated electronics. Stopping occurs due to the closure of the spark plug on the mass, which interrupts spark formation. At the same time, the throttle should block the supply of the fuel-air mixture to the cylinder.
If the engine is still running, one of these processes is disrupted. Either the spark continues to slip due to a breakdown in the ignition module, or the cylinder continues to receive fuel and air. In the second case, the mixture may be so poor that the engine is unstable, but does not stall. Tightness of the crankcase In this case, it plays a crucial role, since any excess air changes the composition of the mixture.
How does the stop button work?
The Stop button on the Stihl MS 180 saw is a simple switch. In the "On" position, the ignition circuit is open, and there is a spark. When switching to the "Stop" position (or releasing the trigger, if configured), the contacts close the high voltage wire on the body, the spark disappears, and the motor dies. If there is no contact, the saw will not die.
It is important to note that in the models Stihl A combined control lever is often used, which simultaneously adjusts the position of the throttle and activates the stop. The mechanical connection between the gas trigger, the suction lever and the stop button can be disrupted due to contamination or wear of plastic elements. A critical factor is the gap between the throttle and the wall of the carburetor in a closed state.Even a microscopic slit allows the engine to work at idle or slightly increased revs.
Diagnostics of stop button failure and electricians
The first step is to find the reason why chainsaw It will not stop, it should be a check of the electrical part. Despite the simplicity of the design, this is often where the banal problems lie. Oxidation of contacts, ingress of moisture or a break in the wire can lead to the fact that the stop command simply does not reach the spark plug.
To check, you must carefully remove the air filter cover and get to the ignition module. Visually examine the wire going from button to coil. If cracks or traces of melting are visible on the insulation, this can cause a current leak. It is also worth checking the button itself: it should be clearly fixed in positions and have an elastic stroke.
- 🔌 Contact check: Remove the wire from the button and lock it on the mass manually. If the saw is stalled, the problem is in the switch.
- 💧 Moisture and dirt: Blow the contacts with compressed air and treat with a spray to clean the contacts (Contact Cleaner).
- 🔥 Candle state: Turn the candle and check for a spark. If there is a spark when the ignition is turned off, the module is pierced.
- 🔧 Wire integrity: Call the wire with a multimeter for a break inside the insulation.
Use dielectric lubrication when assembling electrical contacts – this will prevent oxidation and moisture in the future.
If the electrical part is in order, move on to the mechanics. It often happens that the button is serviceable, but the return mechanism of the valve is jammed. In this case, the engine does not receive a stop signal due to a change in the composition of the mixture. Adjustment of the cable or traction may be required if you notice a backlash or incomplete stroke of the control lever.
Air suction: the main reason for working at high speeds
The most common and insidious reason that Stihl MS 180 It does not stop, it is a sucking of foreign air. The two-stroke engine operates on the thinning created by the piston. If unaccounted holes appear in the system, the mixture becomes poor, and the engine can work even with a completely blocked throttle. This phenomenon is often called “self-ignition work” or simply incorrect work on a poor mixture.
The main places of the potential sucker are in the node of the connection of the carburetor with the cylinder and on the oals of the crankshaft. Over time, rubber seals dry out, crack and lose elasticity. Even a microscopic crack in the drain-manifold It can disrupt the entire engine.
For diagnosis, the spraying method can be used. Get a saw and spray a carburetor cleaner or fuel into the area of the junction of the carburetor and cylinder. If the engine speeds begin to change (usually increase), then the liquid is sucked through leakiness. It is also worth checking the condition of the gasket under the carburetor: it should not be flattened or torn.
The table below shows the main places of the sucker and methods of their elimination:
| Suction site | Symptoms | Elimination method |
|---|---|---|
| Salnick Krival (front) | Oily stains, whistling | Replacement of the oal |
| Carburettor gasket | Unstable idling | Replacement of gasket |
| Intake manifold | Cracks on plastic | Replacement of manifold |
| Salnick Krival (back) | Suction through bearing | Replacement of the oal |
Adjustment of the carburetor and throttle
If the tightness of the system is confirmed, attention should be switched to settings. carburettor. Incorrect adjustment of the screw "L" (low revs) or "H" (high revs) can lead to the fact that the engine can not reset to the level of idling, and the illusion is created that the saw will not decelerate. However, more often the problem lies in the mechanical limitation of the valve.
Remove the carburetor and inspect the throttle. In the closed state, it should fit tightly to the walls of the carburetor chamber around the perimeter. If a gap is visible, even in fractions of a millimeter, enough air will pass through it to keep the engine running. In some models Stihl The position of the valve is regulated by a thrust screw, which can get lost over time.
- 🛠 WINT T: Responsible for the position of the throttle valve at idle. Check if it's too tight.
- 🌀 Cleanliness of channels: Blow all the channels of the carburetor with compressed air. Clogging of chiclairs can distort the work.
- 🔩 Carburettor anchorage: Make sure that the carburetor attachment bolts are tightened evenly and do not deform the body.
☑️ Diagnosis of the carburetor
If you are not sure of your abilities, it is better not to twist the screws "L" and "H" without a pressure gauge and a tachometer. The basic setting can be done by ear, but for an accurate diagnosis of a malfunction associated with the inability to stop, the mechanical state of the valve is more important than the exact ratio of the mixture.
Mechanical problems of the lever mechanism
Often, owners forget about the simple control mechanics. On the handle. chainsaws Style 180 There's a gas trigger and a blocker. When you pull the trigger, it affects the thrust that opens the valve. When you release the trigger, the spring should return the mechanism to its original position. If this process is broken, the saw will not release gas and will not die.
Check if the trigger has jammed. This can happen due to ingress of resin, dirt or wood dust inside the handle. It is also worth examining the return spring: if it is stretched or broken, the spring force will not be enough to close the valve. In some cases, the trigger plastic itself may crack and it stops transmitting force.
What do you do if you pull the trigger?
Take the handle off the saws. Clean the mechanism of old lubrication and dirt. Grease the moving parts with graphite lubrication. If the plastic trigger cracked - replace the part with a new one, gluing will not help due to high loads.
Another reason could be improper assembly after cleaning or repair. If the control thrust is installed in the wrong groove or the sequence of washer installation is confused, the lever stroke will change. Management mechanism You should move freely, without jamming and excessive backlash. When assembling, make sure that all springs fall into place.
⚠️ Attention: Never try to stop a working saw by squeezing your finger at the muffler's outlet or blocking the fuel channel with your finger. This can cause burns, hand injuries or damage to fuel hoses.
The impact of the quality of the fuel mixture on the engine
Although it seems less obvious, the quality of the fuel mix directly affects the engine's ability to stall. If the tank has old fuel that has stood for more than a month, the lighter fractions of gasoline evaporate and a heavy oily sludge remains. The engine can run on this “surrogate”, but the combustion process is sluggish and unstable, which prevents normal stoppage.
Also, the wrong proportion of oil and gasoline (too much oil) leads to soaking on the candle and in the muffler. nagar can create a potassium ignition effect, when the engine continues to work even after the spark is turned off, due to red-hot particles of soda. This phenomenon is dangerous and requires immediate cleaning.
It is recommended to always use a fresh mixture prepared no earlier than 2 weeks before work. If the saw stood for a long time, drain the remaining fuel and try to start it with fresh gasoline. Often the problem “does not stop” is solved by simply replacing the fuel and cleaning the fuel filter in the tank.
The quality of fuel and the absence of coarse in the cylinder is the key to stable operation and correct stopping of the two-stroke engine.
Frequently Asked Questions (FAQ)
Why does the Stihl 180 stop only a few seconds after it is turned off?
This is normal for some modes of operation. After blocking the fuel supply in the cylinder remains a certain amount of mixture, which burns out. If the engine runs for a long time and stalls only when the gasoline in the carburetor runs out completely, then there is an air sucker or a faulty button.
Can I ride a saw if it doesn’t stop with a button?
Absolutely not. The operation of a faulty instrument is prohibited. You lose control of the saw, which in an emergency can lead to serious injuries. Fix the malfunction first.
How often should I change the chainsaw?
The resource of the oil oils depends on the intensity of work and the quality of the fuel mixture. On average, a preventive replacement is recommended every 2-3 years or after 300-500 hours. If there are signs of air suction, the replacement is carried out immediately.
What if the problem persists after the button is replaced?
So it's not the electrician. With a 90% probability, the problem lies in the air sucking through the glands or gaskets, or in the mechanical throttle suction. Diagnose the tightness of the crankcase.