Quick answer
Gas saw: work through fuel, flood, spark, and air, in that order, and keep in mind that stale mix is a common cause behind all of it. Battery saw: the motor is rarely the problem — check the chain brake first (an engaged brake blocks the motor completely), then the battery seating, then the trigger interlock sequence. The full order for each is below.
Gas saws: run the order
1. Fuel first
Two-stroke mix that's been stored a long time is the prime suspect (Stihl's manual says not to store mixed fuel longer than 30 days, so check yours), and mix that wintered in the saw is guilty until proven otherwise. Old ethanol-blend fuel leaves sticky residue that clogs the carburetor's passages as the lighter components evaporate. Dump it, refill with fresh mix at your saw's ratio (or canned premix), and pump the primer bulb if fitted. While the cap is off, check the little in-tank pickup filter — sawdust and fuel gunk plug it, and a starving carb acts exactly like a dead one. Inspect the fuel lines for cracks; a split line sucks air instead of fuel.
2. Flooded? Clear it before anything else
If you've pulled a dozen times with the choke on and now smell raw gas, the cylinder is flooded and no amount of pulling on choke will fix it. Follow the flooded-engine steps in your manual. On Stihl saws that means: set the master control lever or stop switch to STOP, remove the spark plug and dry it, crank the engine several times with the starter to clear the combustion chamber, refit the plug, and restart. Keep sparks and flames away from the open plug hole, and keep the chain brake engaged. Our Stihl-specific guide covers the Master Control Lever sequence, which is where flooding often starts.
3. Spark plug and ignition
Pull the plug. A cracked insulator, burned-away electrode, or heavy carbon crust means replace it — don't ceremony over cleaning a worn plug. Don't test for spark by cranking the engine with the plug out: manufacturers warn that fuel vapor can ignite outside the cylinder. If a known-good plug still won't fire the saw, check that the kill switch isn't stuck in the off position, and have a dealer test the ignition.
4. Air side: filter and spark arrestor
A sawdust-caked air filter riches the mixture until the saw can't fire; tap it out or wash it if the manual allows. And don't skip the spark arrestor — the small screen in the muffler carbons up on saws that spend life at idle, and a blocked screen will let a saw pop but never run. Let the muffler cool, then pull it and clean or replace it. Always shut the engine off first.
5. Still nothing: compression and the carb
A starter cord with no resistance means lost compression — piston or rings, and a repair-versus-replace decision on a homeowner saw. Cord feels normal but the saw still won't run on fresh fuel with a clean filter and plug? The carburetor is a likely suspect: spray-clean it first, then a rebuild kit or replacement carb if the varnish is beyond spray.
Battery saws: interlocks, not engines
A battery chainsaw showing a charged pack that does nothing when you pull the trigger is nearly always one of these, in order:
- Chain brake engaged. The front hand guard pushed forward cuts the motor circuit entirely, and a brake that's only mostly disengaged can still block it. Pull it firmly all the way back toward the handle, cycle it forward and back once, and try again. This is the number-one battery-saw "failure."
- Battery not clicked home. Pull the pack, check the contacts for debris, and reseat until it audibly clicks.3. Trigger sequence. Most saws need the lockout button held before the trigger — done in the wrong order, nothing happens by design.
- Overload protection. An over-tensioned chain or a pinched bar can trip overload; back the tension off a touch and clear any debris at the sprocket.
- Pack verification. Run the battery in another tool on the same platform. Tool runs: saw's switch or interlock is the problem. Tool dead: battery or charger — and remember packs won't charge below roughly 32°F by design.
If all five pass and the saw is still silent, the trigger switch or an internal interlock has failed — warranty territory on anything young. Chain turning but won't cut, or motor runs and the chain doesn't? Different problem: see the chain won't spin guide.
Keep it from happening again
Gas saws die in storage, not in use. Either run the carb dry before a long layoff or store it on stabilized or canned fuel; drain-and-fresh every spring beats a carburetor job every second one. Battery saws just want the pack stored indoors, partially charged, and away from freezing.