Chainsaw — Won't Start

Before you begin

Keep the chain guard/scabbard on until the saw is running and ready to use. Wear gloves and eye protection. Keep hands clear of the chain during every check, and always start the saw on the ground or braced firmly, never in the air.

Spark plug test — safety first

Keep the plug pointed away from the plug hole and any spilled fuel while testing spark.

Chain brake engaged

The chain brake is a safety interlock on many saws — with it engaged, the saw either won't start or the throttle won't respond, by design.

1. Pull the chain brake lever back toward the front handle to disengage it — you should feel/hear it click free.
2. Confirm the chain can spin freely by hand (with spark plug disconnected) before starting.

Incorrect or missing 2-stroke oil mix

2-stroke engines rely on the oil mixed into the fuel for internal lubrication. Straight gasoline, even briefly, risks real engine damage beyond just a no-start.

1. Drain any straight or incorrectly mixed fuel completely.
2. Mix fresh gas with 2-stroke oil at the ratio in your owner's manual (commonly 50:1 — confirm for your model).
3. Use a marked mixing bottle rather than eyeballing the ratio.
4. Note this is separate from the bar and chain oil reservoir — don't confuse the two oils.

Parts that may help: 2-stroke engine oil, marked fuel mixing bottle

Stale 2-stroke fuel mix

2-stroke mix degrades faster than straight gas as the oil separates out — a very common cause of a saw that sat in the garage all winter refusing to start.

1. Drain old fuel into an approved container.
2. Mix a fresh batch at the correct ratio.
3. For future storage, mix only what you'll use in 30 days, or use a fuel stabilizer rated for 2-stroke mix.

Parts that may help: 2-stroke engine oil, e.g. Sta-Bil, Sea Foam

Cold-start procedure not followed, or flooded

Chainsaws need a specific choke sequence — leaving full choke on too long is one of the most common ways to flood a saw that would otherwise start fine.

1. Set choke to full/cold-start, pull sharply until it fires or sputters (usually 2-5 pulls).
2. As soon as it fires or almost catches, move the choke to half/run and continue pulling.
3. If you suspect it's already flooded (smells strongly of fuel, won't fire at all), set the choke to run/off, hold the throttle wide open, and pull the cord several times to clear the excess fuel before trying again.

Faulty on/off switch or wiring, not the ignition coil

Since spark returned once isolated, the coil is fine — the switch or its wire is grounding out ignition even in the 'Run' position.

1. Inspect the switch's internal contacts for corrosion — common after a season of sawdust and weather exposure.
2. Check the wire's full length for cuts, fraying, or a loose connector at either end.
3. Replace the switch if wiring checks out — a straightforward, low-cost swap on most saws.

Parts that may help: replacement on/off ignition switch

Faulty ignition coil

Since spark still didn't return with the kill circuit isolated, the coil is the likely failure point.

1. Clean the flywheel magnets and coil laminations with fine sandpaper if accessible.
2. Check the coil's air gap against your engine's spec with a feeler gauge if adjustable.
3. If that doesn't restore spark, replace the ignition coil.

Parts that may help: engine-model-specific ignition coil, feeler gauge set for coil air gap

No spark — plug or ignition coil

Start with the plug, since it's the cheaper and far more common failure point.

1. Replace the spark plug with the correct type/gap for your model.
2. If a new plug still gives no spark, the ignition coil likely needs testing with a multimeter or replacement.
3. Also confirm the on/off switch is set to run — an easy thing to overlook.

Parts that may help: engine-specific spark plug, engine-model-specific ignition coil

Fouled or flooded spark plug

A wet, fuel-smelling plug points to flooding, usually from too much choke time.

1. Remove the plug, wipe clean or swap for a fresh one.
2. With the plug out, set choke to run and pull the cord several times to clear excess fuel.
3. Reinstall the plug and retry with the choke procedure above.

Parts that may help: engine-specific spark plug

Clogged air filter

Sawdust clogs chainsaw air filters faster than most other small engines, especially in dry cutting conditions.

1. Tap out debris and brush clean; wash foam filters in warm soapy water and let fully air dry.
2. Replace if torn or heavily saturated.
3. Check it every few tanks of fuel if cutting dry or dusty wood regularly.

Parts that may help: engine-model-specific air filter

Stuck or leaking compression release valve

This valve is designed to bleed off some cylinder pressure during starting to make pulling easier, then seal fully once running. If it's stuck open or not sealing, the engine effectively loses compression right when it needs it most to fire.

1. Inspect the valve for carbon buildup preventing it from seating — clean with carb cleaner spray if accessible.
2. Replace the valve if it's cracked or the spring has weakened — a bolt-on part on most saws that have this feature.

Parts that may help: compression release valve

Possible crankcase seal leak — needs pressure/vacuum testing

Without a pressure/vacuum tester, a crankcase seal leak can't be reliably confirmed at home, but it's a common cause of a saw that has fuel, spark, and a clean carb yet still won't run.

1. This is a good candidate for a local small engine shop — this specific test is quick for them to run and will confirm or rule this out.

If this doesn't resolve it, this is a good candidate for a local small engine shop rather than continued DIY diagnosis.

Crankcase seal or gasket leak

A leaking crankcase can't build the pressure needed to pump the fuel/air mixture properly, preventing reliable running even with good fuel and spark.

1. Common leak points are the crankshaft seals and the carburetor mounting gasket.
2. Replacing crankshaft seals typically requires splitting the crankcase — a substantial repair best left to a shop unless you're experienced with 2-stroke rebuilds.

Parts that may help: crankshaft seal kit

If this doesn't resolve it, this is a good candidate for a local small engine shop rather than continued DIY diagnosis.

Low cylinder compression — piston or cylinder wear

With crankcase sealing, fuel, and spark all ruled out, low cylinder compression points to worn piston rings or cylinder wear.

1. Given the teardown involved, this is worth a shop's opinion on repair cost versus the saw's value before investing further time yourself.

Parts that may help: small engine compression tester

If this doesn't resolve it, this is a good candidate for a local small engine shop rather than continued DIY diagnosis.

Needs professional diagnosis

You've ruled out chain brake, fuel mix, choke procedure, spark, air filter, compression release, crankcase sealing, and (if tested) compression. Remaining causes are specific enough to your model that a shop's equipment will resolve this faster than continued guessing.

1. This is a good candidate for a local small engine shop — bring your notes on what's already been ruled out.

If this doesn't resolve it, this is a good candidate for a local small engine shop rather than continued DIY diagnosis.