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Petrol chainsaw will not start: the causes two makers' service pages list

Makers' support pages sort a petrol saw that will not start into a short list of causes: flooding, fuel, fuel delivery, spark, air and exhaust. This page sets out the list one maker prints, the starting sequence another prints, and what the regulators read say about starting a saw.

Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.

This page reports what the named codes, regulators and makers say. It is not training and does not teach the work. This page reports what the official source says. It is not legal advice: ask the office named here. Each saw's own manual sets the detail for that saw, and the makers' pages say a dealer or service centre handles what is beyond the simple checks.

The courses that teach saw maintenance are covered in the guides on chainsaw tickets and the UK maintenance and crosscutting award. Fuel itself is covered in the guide on fuel mix and ethanol.

Causes one maker lists

One maker's United States support article on a gas engine that will not start or is hard to start lists these common causes. The article is undated on the page.

AreaWhat the article says
Flooded engineThe most common cause with new engines. It can follow several pulls of the starter rope with the choke closed. The engine may briefly pop and then stop
Fuel and oilFresh fuel less than 30 days old, rated 89 to 93 octane, and free of water or debris. Oil that meets ISO-L-EGD and JASO M345 FD. Mixed at the ratio in the operator's manual
Fuel deliveryFuel lines with cracks, kinks or blockages, a restricted fuel filter, and a purge bulb that is cracked or does not fill
IgnitionA spark plug that is fouled, damaged or has the wrong gap, a loose plug boot, and loose, pinched or damaged ignition wires
Air intakePre-filter, air filter and filter base that are not clean
ExhaustHeavy carbon build-up on the spark arrestor screen and exhaust port

The article then lists causes it says need an authorized dealer: a carburetor, if fuel stayed in the unit for more than 60 days before storage or the unit works above 5,000 feet (1,524 m); a failing ignition coil or module; and internal damage or overheating, which it ties to fuel below the rated octane or debris in the cooling fins. It says diagnosing and repairing these needs specialized tools and expertise.

The starting sequence another maker prints

A second maker's United Kingdom page on starting a chainsaw (dated January 25, 2026) sets out a sequence for a saw without its electronic engine management. It reports these points, among others:

  • The chain brake is engaged and the scabbard removed before starting.
  • A decompression valve, if fitted, is pressed, and a manual fuel pump bulb is pressed several times.
  • The master control lever is set to the choke or cold start position, with the saw on level ground and the cutting attachment clear of it.
  • The starter cord is pulled slowly until resistance is felt, then forcefully several times until the engine fires.
  • The page says the engine will then only briefly come to life and stop. The choke is opened by moving the lever up one position to half throttle, and the cord is pulled again.
  • The page says refuelling is at least 3 metres from where the saw is used, and that petrol saws give off toxic fumes from the moment the engine starts, so they are used outdoors or in well-ventilated spaces.

What regulators say about starting

OSHA's logging standard, 29 CFR 1910.266(e)(2), says a saw is started on the ground or where otherwise firmly supported, drop starting is prohibited, and the saw is started with the chain brake engaged. CCOHS says the saw should idle without the chain turning, and that if the chain keeps turning after the throttle is released the saw is stopped and the idle adjusted as the owner's manual shows. The full lists of checks are in the guide on chainsaw checks before and during use.

Sources