Chain Saw: Starts, Runs For A While, Then Dies

Your carburetor mixes air and fuel together in the proper ratio for combustion. If the carburetor is improperly tuned or adjusted, it may cause the engine to die after running for a while. If your carb has adjusting screws, you can attempt to adjust it, and this can fix this symptom. Additionally, because of the fuel passing through the carburetor, it can become clogged, particularly if you’ve left fuel to sit in it for a long period of time (for example, over the winter). Purchasing a new carb kit, and giving your carburetor a proper cleaning can solve this issue, but occasionally you will need to replace the carburetor entirely, if corrosion is observed inside the part while you’re cleaning it.

Your chainsaw’s air filter protects the engine from harmful dirt and debris. Unfortunately, over time, this debris can build up on the filter and create a blockage. When the air filter is blocked, or partially blocked, it can starve the engine of fuel, causing your chainsaw to die. How long the chainsaw runs before dying depends on how badly clogged the air filter is. In the case that your chainsaw runs for a while, then dies, it may be possible to simply clean the air filter to correct this symptom. However, a damaged air filter should be replaced. Regular checks of the air filter for buildup should be part of your regular chainsaw maintenance routine. To access it, look to the top of the carburetor. The air filter is easily located.

Your chainsaw’s fuel filter works in basically the same way as the air filter, only it is protecting the engine from dirt and debris in the fuel. Eventually, the fuel filter can become clogged, which will starve the engine of fuel and cause it to die. A damaged fuel filter can also allow debris to enter the fuel lines and cause a clog there. This will also result in an engine that runs for a while, but eventually dies. Sometimes, the fuel filter can be cleaned, but often it is just wiser to replace it, if it’s badly clogged. Fuel filter maintenance and replacement should be a regular job.

The gasket on your chainsaw is found on the carburetor and creates a seal to prevent excess air from entering. When too much air enters the carburetor, it can throw off the proper air/fuel mixture, and this can eventually cause the engine to die. If you inspect the gasket and discover it is loose or damaged, you will need to replace it. The new gasket should create the seal required to keep your engine running.

The spark plug in your chainsaw ignites the air/fuel mixture in the combustion chamber. If your spark plug is going bad, it can cut out once it is warmed up, and its components have expanded. Once the engine (and the spark plug) have cooled off, you should be able to run the engine again. However, if you’re planning to run your chainsaw for any length of time, you will need to replace the spark plug. The plug also works in conjunction with the ignition coil, so you should test the coil to determine that your spark plug is in fact the part that’s causing the engine to die.

A worn or damaged piston and cylinder will cause this problem. As the engine runs, heat will build. Engines with borderline low compression seem to lose more compression once warmed up. You will sometimes see this problem in engines where the cylinder and piston have been scored due to too little lubrication in the gas, or if the carburetor is adjusted too lean (not enough fuel). When cool, the engine will turn over. Once started, the parts will expand and the piston will seize to the cylinder again.

Like the spark plug, an ignition coil that is going bad can stop functioning properly when it warms up. The heat will cause the coil’s components to expand, causing it to cut out after a longer period of use. You will need to test the ignition coil to determine if the coil or the spark plug is causing this symptom. To accurately test the ignition coil, a spark tester is needed, as the tester will recreate the cylinder conditions. Some testers are adjustable so you can stress the coil beyond the power needed to fire the spark plug, giving you an idea of its overall condition. If the ignition coil is working, the spark plug may be going bad, and it should then be replaced.