Why does the chainsaw quit when idling?
Why the chainsaw stops when you press the gas
Although the chainsaw is a very simple machine, it does occasionally have problems that can only be corrected by disassembly and reassembly. Examples of faults are as follows:
- The chainsaw won’t pick up speed;
- The chainsaw stops functioning while cutting;
- Chainsaw starts and stops;
- The chainsaw loses its power;
- Chainsaw malfunctions when pulled.
Most often the faults are associated with malfunctions of the motor, as well as with the failure of other systems and components. Proper handling of the machine is important. If all the rules of use are followed, problems are likely to be the most obvious. When searching for the cause of trouble, it is best to begin with checking the simplest part of the chainsaw and end with the most complex one.
Probable causes of faults
All chainsaws are powered by a single-cylinder internal combustion engine. This type of devices is characterized by such malfunctions, as violation of intra-cylinder compression, change of fuel mixture ratio, incorrect ignition operation, poor-quality fuel and lubricants. The main problems with the power unit are as follows:
- the engine steadily runs at minimum rpm, but stalls when the rpm is increased;
- Starting is normal, but idle rpm is unstable, rapidly throttles;
- does not start.
Diagram of electronic ignition of a chainsaw.
Unsteady idling can be caused by a variety of reasons. They can be divided into several positions:
- reduced capacity of filters (gasoline and air);
- abnormal operation of the ignition system:
- the carburetor settings have changed spontaneously;
- Faulty gasoline line components;
- clogged exhaust ducts, muffler;
- piston, cylinder, valve defects.
Repair should begin with an external inspection and check the presence of fuel in the tank.
Why does the carburetor idle
The 1st and most common cause of this malfunction is improper carburetor adjustment. To carry out the adjustment of the idle speed is an option without assistance from others, for this purpose need to have a screwdriver STIHL, which comes with the unit. The adjustment hole is on the right side of the STIHL 180 saw on the handle and is marked with “-” and “”.
If your STIHL chain saw does not hold rpms and stops idling, of course there is about 90% certainty that it has a fault in the fuel pump system, usually an air leak in the crankcase through the sump gasket or, more often, through the crankshaft oil seals. Air suction lowers or shuts off completely the impulse that is delivered through special channels to the gasoline pump. STIHL 180 chain saw will not get enough fuel and will shut down at idle.
To make a diagnosis, you can use a special device, which is called a vacuum gauge.
The second method to test the functionality of seals, is to pour gasoline into the crankcase and look at them, if the seals will skip gasoline, so they to provide the usual pressure in the crankcase, which will make the work at idle will not be feasible. And during work at high revolutions, with leaking seals, there is a possibility of jamming of the crankshaft bearings.
Checking the STIHL oil box and oil seals
- Remove the top cover.
- Remove the air cleaner housing and carburetor.
- The chainsaw handle is removed.
- Unfolds and retracts the starter.
- On the reverse side of the starter, remove the side cover and the drive sprocket.
- In the spark plug hole installed piston stopper on the other in the cylinder is stuffed with string from the starter with the knots tied to him.
- The flywheel and the clutch are unscrewed, then the parts are removed. It is worth knowing that the clutch chainsaw has a left-hand thread and unscrewed in a clockwise direction.
- The gear wheel of the oil pump drive is removed.
After taking the STIHL MS 180 chain saw apart you can find the oil seals and after that you need to fill the sump with gasoline and check for leaks. Fill the crankcase, it is possible through the fuel window in the cylinder, for this purpose, the piston must be raised very high. If any leaks are detected, the defective seals should be replaced or the sump should be sealed again. To assemble the STIHL 180 it is possible to observe the reverse sequence of the method.
Why the chain saw doesn’t pick up speed?
Starting up. This is a complex multi-level process that involves almost all life support systems. This is why the fact that the chainsaw loses speed, occasionally turns on and feels confident only at idle should be considered from different angles.
The following factors may cause this:
- Defective engine. Its service life may be extended, and the piston rings and cylinder may be worn, deformed, or even corroded;
- Faulty spark plug or coil itself. As a result, the spark needed to ignite the fuel-air mixture is not formed;
- Carburetor imbalance screw, and a number of reasons that may have disabled it.
The chainsaw does not drop the rpm
In some cases the chainsaw quickly reaches a certain power level and does not decelerate. It is not enough to adjust the screws on the frame or clean the carburetor. The problem lies in the high consumption of fuel mixture.
The following steps are performed:
- Check if the throttle cable is working;
- Inspects the return spring. it may be slipping;
- The choke must be completely tight.
Why the chain saw doesn’t pick up speed and shuts down
If the chainsaw is not able to rev or stops after a minute of starting, the carburetor or crankcase is most likely leaking. As in the previous case, the problem can be solved by checking and adjusting the carburettor for leaks.
If the chainsaw does not pick up speed and shuts down after it has been running normally for about 5 minutes, the cause may be a defective fuel tank breather. The vacuum created in the fuel tank while the tool is running does not allow the engine to receive the amount of fuel necessary for normal engine operation and, therefore, the engine will be unable to rev up or stall. If you stop the tool, open and close the fuel tank lid and restart the chainsaw, the tool will operate normally again for about five minutes, after which it will stop revving or will choke.
If the chainsaw does not pick up speed, it may be caused by excessive soot in the muffler, which prevents the exhaust gases from escaping, thereby reducing engine power and speed.
If you want to check the tightness of the crankcase, but do not have a special tool, you can use the following technique.
Algorithm for checking the crankcase for leaks
- Removing the side cover and guide bar from a chainsaw.
- Unscrew the spark plug and through the spark plug hole lay a string with knots in the cylinder, thereby stopping the movement of the piston and crankshaft.
- You can use an old starter cord and knot it with knots every 3 to 5 cm.
- Unscrew the chain saw‘s drive sprocket.
- Remove the oil pump cover and the pump itself.
- Remove the starter from a chainsaw.
- Unscrew and remove the flywheel.
- Remove the carburetor.
- With a syringe, through a hole under the carburetor in the cylinder, pour gasoline into the crankcase, while watching the crankshaft oil seals. If you notice gasoline leaking through them, they are in bad shape and should be replaced.
- It is better to leave the installation of the seals to professionals.
An indirect sign of a leaky crankcase is oil leaks around the oil seals.
Signs of typical failures
If your chainsaw fails to rev up and shuts down, has poor power and shuts down under load, it could be a fuel shortage or a bad carburetor adjustment.
In the list of possible reasons. dirty fuel filter or air intake filter element, too rich or too lean petrol-air mixture.
Signs of running of the engine on a rich mixture:
Chainsaw cuts out when throttle. mixture is probably too lean.
Faults of the cylinder-piston group
It is possible that even after all the above troubleshooting is corrected, your chain saw will continue to idle or won’t start at all. In this case it is necessary to look into the very heart of an engine. its cylinder.
Sometimes even a visual inspection is enough to determine what is wrong with the cylinder-piston group. Chips, scoring, evident cylinder wear and other visible defects are the direct obstacles for normal operation of the device. Without any doubt, such parts should be replaced.
If there is no obvious damage, you need to examine the piston rings. It is damage to these rings that causes loss of engine power. The rings in the cylinder grooves move too freely, indicating that it is time to replace these parts with new ones.
Meanwhile it is possible to get a complete idea about the technical condition of this group of parts only after a complete disassembly of the engine. As it is a labor-consuming, responsible job that demands a certain professional experience, it is better to entrust it to a specialist. This is the only way to prolong the working life of the chainsaw, the big helper of man.