Lawn Mower Cranks but Won't Start? Check the Gas First

The engine turns over but never catches

A gas mower needs air, fuel and a spark at the right moment, and if any of them is missing, the engine won't start (opens in a new tab). We'd check how old the gas is before buying any parts, because Briggs & Stratton calls stale fuel, dirt and debris the most common cause of outdoor power equipment not starting, and Toro calls old fuel in the tank the leading cause of hard starting.

These checks are for a gas walk-behind mower whose engine turns when you pull the cord. A cord that's hard to pull or feels stuck is a different problem, and Briggs & Stratton says a typical cause is the bar on the handle not being held all the way down.

Check the gas first

Think about when you bought the gas and how it's been stored. Old gas can cause starting problems (opens in a new tab), and fuel stabilizer won't rescue it. Stabilizer only works if it goes in on the day you buy the fuel, and it won't make old fuel fresh again.

If your mower has a fuel valve, make sure it's on. An empty tank or a valve left off will stop it starting too.

If the gas is old or you don't know how old it is, have a service dealer replace it before you try again. Don't tip the mower to empty the tank or siphon the fuel yourself.

Check the spark plug wire and air filter

Work on level ground outdoors. Before you touch the engine, shut it off, wait for everything to stop moving and let it cool, then pull the wire off the spark plug. Wear gloves and eye protection, and keep your hands and feet away from the blade and out from under the deck.

A loose or disconnected spark plug (opens in a new tab) can stop a mower starting, so when you've finished these checks, push the wire firmly back onto the plug.

A clean air filter makes the engine easier to start (opens in a new tab), and a dirty one makes it harder for the engine to draw in air. Filters can be paper, foam or dual-element, and each type is cleaned differently, so follow your engine's manual for yours.

While the engine is cold, check the oil level too. Add oil if it's low, but don't go over the full mark, because too little or too much oil can damage the engine. Never tamper with the mower's safety controls.

Use your engine's starting routine

Starting routines vary. Some Briggs & Stratton engines need no priming and no choke at all (opens in a new tab), while its Prime 'N Pull engines skip the choke but need three presses of the primer. On a Honda HRC216HXA or HRC216HXPH, you turn the fuel valve on, set the throttle lever to CHOKE for a cold engine or FAST for a warm one, then pull. Some mowers also need the control bar held against the handle while you pull, so check your manual before you prime, choke or pull.

Toro and Honda say to pull the cord lightly until you feel resistance, and Briggs & Stratton says to pull it slowly. From there, all three say to pull fast. Toro and Honda add that you should ease it back instead of letting it snap back.

Start the mower outdoors on level ground, since the exhaust contains carbon monoxide, with the area clear of objects, children and bystanders and all the guards and safety devices in place. Wear eye protection while you pull. If it won't start after several attempts, stop and take it to a service dealer.

What else keeps a mower from starting

When fresh fuel and those checks don't get it running, the cause may be inside the engine's fuel or ignition system. Stale gas can clog the carburetor, which Briggs & Stratton calls a common issue. A clogged fuel filter can keep enough fuel from reaching the engine, and a fouled or faulty spark plug, or one wet with fuel from a flooded engine, can stop it firing.

Honda sends fuel filter, carburetor and ignition faults to a servicing dealer (opens in a new tab), and checking a spark plug means taking it out of the engine. For any of these, take your mower to a service dealer or a small-engine mechanic.

On a Toro 21462 Recycler

These details are for the pull-start Toro 21462, serial 408930000 and up, so match both numbers to Toro's operator's manual (opens in a new tab) first.

Toro wants clean, fresh unleaded gas that's no more than 30 days old and meets all of these:

• At least 87 octane in the US, or 91 research octane outside the US
• No more than 10% ethanol by volume
• No methanol, and less than 15% MTBE by volume
• No oil added to the gas

Add fuel stabilizer to fresh fuel as its maker directs. Fill only to the base of the filler neck, keeping fuel out of the neck itself, then put the cap back on.

Check the oil before each use with the mower level and the engine off and cool. Unscrew the dipstick, wipe it clean, screw it back in, then unscrew it again and read the level. It has to sit within the marked range, because too little or too much oil can damage the engine, so have it corrected before you start the mower if it doesn't. Replace and tighten the dipstick when you're done.

If the handle was recently unfolded, make sure the cables run outside the handle without being pinched. If a cable is damaged, stop and contact an Authorized Service Dealer.

Service the air filter every 25 hours and replace it yearly, more often in dusty conditions. With the spark plug wire still off, unclip the top of the cover and take out the filter. Replace it if it's very dirty, or tap it gently on a hard surface to loosen debris. Put it back, clip the cover shut and reconnect the spark plug wire before you try to start it.

1. Check that the air filter and cover are back in place, the spark plug wire is connected and the starter rope sits in its rope guide.
2. Hold the blade-control bar against the handle.
3. Pull the recoil-start handle lightly until you feel resistance, then pull sharply, and let the rope return slowly.
4. If the engine doesn't start after several attempts, stop and contact a Toro Authorized Service Dealer.

Once it starts, let go of the bar. The engine should shut off and the blade should stop within 3 seconds. If they don't, stop using the mower right away and contact an Authorized Service Dealer. Wait for all moving parts to stop before you leave the handle, and keep away from the hot engine and muffler.

When it still won't start

If fresh fuel and the normal starting routine haven't worked after several attempts, take it to a service dealer or small-engine mechanic. We'd skip buying parts to try at home, because the causes left at this point, like the carburetor, fuel filter or spark plug, all mean working on the engine.

Toro owners can contact a Toro Authorized Service Dealer or Toro Customer Service. Have the model and serial numbers ready, and tell them what happens when you pull the cord, when the mower last ran normally, how old the fuel is, what blend it is and how it was stored, which checks you've done (air filter, oil, spark plug wire), and any damaged cable, impact or unusual vibration.