Why won't my chainsaw start?
A chainsaw that will not start almost always comes down to fuel, spark, or air, and on gas saws the fuel is the usual suspect. Petrol degrades within weeks, and stale or wrongly mixed fuel either will not ignite or gums up the carburettor, so start by draining old fuel and refilling with a fresh mix at the ratio your saw specifies.If fresh fuel does not fix it, work through the other basics in order. Pull the spark plug and check for heavy black or oily fouling; clean or replace it and confirm the gap matches the manual. Remove the air filter and clean it if it is clogged, because a starved engine will not fire. Make sure you are following the correct cold-start choke sequence, as skipping or overdoing the choke leaves the engine either dry or flooded.
How do you start a flooded chainsaw?
A flooded chainsaw, one that smells strongly of petrol and will not fire after several pulls, has too much fuel in the cylinder for the plug to ignite. Clear the excess before trying a normal start, rather than pulling harder, which only floods it further.- Move the choke fully off, to the run position, so no more fuel is added.
- If your saw has a decompression valve, press it, and set any fast-idle or start throttle as the manual directs.
- Hold the throttle wide open and pull the starter cord firmly six to ten times to draw air through and clear the excess fuel.
- If it still will not fire, remove the spark plug, dry it, crank the engine a few times with the plug out to expel fuel, then refit the dry plug.
- Start with the choke off and the throttle open; it should fire, then settle to idle.
Flooding most often comes from over-choking or repeated pulls on full choke, so getting the cold-start sequence right prevents it.
What is the correct cold-start sequence for a gas chainsaw?
Starting a cold gas saw in the right order prevents both a dry no-start and a flood. Sequences vary between models, so the manual is the final word, but the typical pattern is consistent across most saws.- Engage the chain brake and set the saw on firm ground, with a foot in the rear handle and a hand on the front handle.
- Press the primer bulb, if fitted, several times until fuel is visible.
- Set the choke to the full, cold-start position.
- Pull the cord until the engine coughs or fires once, then move the choke to the half or run position.
- Pull again to start, blip the throttle to settle it to idle, and release the chain brake only when you are ready to cut.
Skipping the choke leaves a cold engine too lean to fire, while leaving it on full choke once the engine has caught is what floods it. Getting this sequence right resolves a large share of no-start complaints on a saw that is otherwise healthy.
Why won't a battery or corded chainsaw start?
A cordless or corded chainsaw that will not run is usually held up by a safety interlock or the power supply rather than an engine fault, so the checks are quick. Most cordless saws will not start with the chain brake engaged or the battery low.- Confirm the battery is charged and clicked fully into place, and try a second pack if you have one.
- Release the chain brake, since many cordless saws disable the trigger while it is engaged.
- Check you are pressing the safety lockout and the trigger together, as required.
- For a corded saw, confirm the outlet, the extension lead, and any reset button on the plug are all live.
- Let a very hot or very cold battery return to room temperature, as some packs cut out at temperature extremes.
If the saw still will not run with a known-good, charged battery and the brake released, the fault is likely in the switch or motor and needs a service. Our battery chainsaw guide covers pack care and common cordless issues.
When is a chainsaw no-start a job for a technician?
Take a no-start to a technician once fresh fuel, a good spark plug, a clean air filter, and the correct starting sequence have all failed to bring the saw to life. At that point the fault usually lies in the carburettor, the ignition coil, or the crankcase seals, none of which are quick driveway fixes.A saw with no spark at all despite a known-good plug points to the coil or the kill switch, while one that has spark and fresh fuel but still will not fire may have a carburettor blocked with varnish or an air leak leaning it out. These need the right tools and a proper diagnosis. Our chainsaw maintenance guide covers the full fuel and filter routine, and always wear chainsaw chaps and PPE when running a suspect saw. This is general troubleshooting guidance, not a substitute for hands-on training.
