Why won’t my chainsaw stay running?
Your chainsaw won’t stay running because of gas, oxygen, compression, exhaust, and/or spark. The absence of any one of these elements will result in the engine failing. So, an engine that starts and then dies means that one of these elements is lacking.
Here are the tests that will resolve the problem…
Prime suspect: Fuel Supply
A choke is designed to ensure that there is sufficient fuel to start the engine. Many chainsaws use the choke in the preliminary sequence in starting engines. It’s a common method.
Choke on and a couple of pulls on the starter cord and when the engine begins to fire the choke is switched off and the engine fires up on the next pull using the standard fuel mixture.
Checking the fuel supply is relatively easy and the most obvious first stop would be with the fuel filter.
Most chainsaws have a weighted fuel filter attached to the flexible supply pipe located in the gas tank.
The filter is weighted to ensure that the pipe intake is always at the lowest point in the tank irrespective of the angle the chainsaw is being used at. This ensures a continuous supply of fuel to the carburettor.
Pull the fuel filter out of the tank. You may need a short wire hook to do this to avoid having to turn the engine over and splashing the residual fuel over your work surface. Check the filter and consult your diary when last you replaced the filter.
If you didn’t write it down and you can’t remember, well then you need to replace the filter. They’re cheap and the extra trip to the supplier will serve as a reminder to buy two so you will have one spare.
Next, check the flexible pipe from the filter to the carburettor. Make sure there are no cracks or breaks in it and if it feels a little sticky, chances are you would do well to replace it.
With a new filter and a pipeline in good condition,
it would be a good time to test the engine out and if it starts and runs now, then you have solved the problem but if not, you will have to carry out further maintenance.
Dirty Air Filter
Gas by itself will not get your engine running smoothly. It needs oxygen as well and in the correct proportion to the gas. A dirty air filter destroys that combination and will result in your chainsaw not performing.
Cleaning the air filter is a simple process but also see if the air filter needs replacing. Many air filters can be cleaned repeatedly, but some models will respond positively to a new filter.
You may also want to check the low and high setting screws and for this you will have to check your chainsaw manual for the correct settings.
Normally this will involve turning the screws right in and then a specific number of turns out. Often it will be one and a half turns out but do check your owner’s manual.
If the chainsaw has had a long rest and starts but does not run, then cleaning the carburettor may be required. A quick check is to start the chainsaw and keep the choke on to see if the engine will run with the choke on. If it does then the carburettor requires cleaning.
Fortunately, there is no need to take the carburettor apart because a handy aerosol of carburettor cleaner is available. It can be used to spray into the air intake of the carburettor, and it will clean out all the little nooks and crannies that are so difficult to get to.
Do take care when spraying with the cleaner as it is quite aggressive on some materials. Reading the instructions is always a good idea.
Start the chainsaw and check if the spray has done its job. It may take more than one application and be sure to fill up with fresh fuel.
Dirty Spark Arrestor
To get to the Spark Arrester will require some removal of the exhaust system. Depending on the chainsaw you have the spark arrester will be located somewhere along the exhaust line.
Some arresters are easily removed by being secured at the end of the exhaust line and if this is the case with your machine, then the repair is easy.
The Spark Arrester is the part that prevents sparks from flying out of your chainsaw and setting the forest alight. It sadly also prevents a number of other solids and sometimes liquids from leaving the exhaust line, so it tends to get clogged up.
The typical symptom of a blocked Spark Arrester is the engine will start but will die as soon as the throttle is depressed.
To get your chainsaw back to life remove the spark arrester and give it a good clean with a soft wire brush and perhaps a little cleaning fluid if it is really choked up. Replacing it is also an option but don’t be tempted to discard the Spark Arrester.
It will not only be seriously dangerous, but your engine exhaust is designed to accommodate the restriction of the Spark Arrester.
Once the Spark Arrester has been cleaned and replaced or a new one fitted, try the engine again and if it runs and revs up you can give yourself a healthy pat on the back for a good job done.
Two final checks
All the above faults have a common connection in that they impinge upon the correct fuel supply. The fact that the engine starts means that there is sufficient spark, but it is always worth removing the spark plug and giving it a quick clean.
It has been operating in an environment not conducive to optimum performance so, a little sprucing up will be well timed.
Fuel in a can has a limited shelf life so, once you have got your chainsaw starting and running well again have a look at the fuel. If it is from last season, then best replace it with fresh fuel and make sure that the fuel to oil mixture is as per the specifications.
This will ensure good performance from your chainsaw.