Chain Saw: Hard To Start

The carburetor is an important part to your chainsaw’s operation, as it provides the fuel and air mix that the engine requires for combustion. If the carburetor becomes plugged, it will not provide the correct mix, or any fuel/air at all, and this makes the engine hard to start. Often, the carburetor will become clogged because of fuel sitting in it for a long period of time (for example, over the winter months). You may be able to take the carburetor apart, clean it properly, and potentially replace some of the smaller interior parts with a new carb kit. This should help unplug your carburetor, and get your chainsaw running smoothly again.

Your chainsaw requires a clean air filter to start efficiently. Because the air filter is designed to collect dirt and debris, and prevent it from reaching the engine, this debris can build up and create a clog. A clogged air filter will not allow enough air to reach the engine, and this will create a less-than-ideal environment for combustion. This will make your chainsaw difficult to start. Fortunately, the air filter is easily removed and replaced when it becomes clogged. Simply take it out of the top of the carburetor by the tabs or screws that are holding it in position, and replace it with a new one. If you clean your air filter regularly as part of your normal maintenance routine, you can help avoid replacing it as regularly, but annual replacement is part of good chainsaw maintenance.

Your chainsaw will have a fuel filter that is connected to the fuel lines, and rests within the fuel tank. It is designed, like the air filter, to keep dirt and debris out of the carburetor and the engine. As it blocks this debris, it can become clogged, and this will prevent fuel from reaching the carburetor. As a result, the engine will be difficult to start, even if the fuel tank is full. The fuel filter can be disconnected form the fuel lines, and either replaced or cleaned thoroughly to prevent this issue. In some cases you’ll need a hook to remove the fuel filter from the tank. Cleaning the fuel filter should be part of routine chainsaw maintenance.

Your spark plug ignites fuel in the combustion chamber, and this is what powers your chainsaw. A rich-running engine (too much fuel in the air/fuel mix), can allow carbon deposits to build up on the spark plug. When this occurs, the spark plug is considered fouled, and will cause difficulty starting the engine. An engine that becomes flooded can also develop similar deposits, and this will also make your engine difficult to start. A fouled spark plug will need to be replaced before you can start your engine easily again. When you’ve finished cleaning the part, or if you’re installing a new one, make sure you re-gap it to the manufacturer’s specifications as you put it in place.

The primer bulb on your chainsaw’s carburetor creates a vacuum that pulls fuel from the fuel lines into the carburetor. If the primer bulb is cracked, it will not be able to create the required vacuum, and this will prevent it from priming the carburetor. A cracked primer bulb could cause a two-fold issue. Not only will it not draw enough fuel into the carb, but it could pull air from outside the bulb in through the cracks, causing the air/fuel ratio to be off.

Fuel lines transport fuel from the chainsaw’s fuel tank into the carburetor. The primer bulb creates a vacuum with allows the fuel to travel along the lines and into the carburetor. These lines are usually made of rubber or plastic, and therefore they can develop cracks over time. If they are cracked, you will notice fuel leaking from the lines, and your chainsaw will be difficult to start, due to a lack of fuel. Fuel lines are easy to replace; simply disconnect the lines from the carb and the fuel filter, then replace them with new lines. This is a fire hazard, so ensure cracked lines are replaced immediately. Another possibility is that the lines are blocked, which you should be able to test for by gently pulling them off in a twisting motion on the carburetor end and the fuel tank end, and blowing through them, looking for any strange debris to come out as you do. If you feel the lines are heavily blocked when blowing through them, you should replace them.