How to Fix a Flooded Engine on a Mower, Trimmer or Saw

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Last updated October 28, 2026 · Applies to: lawn mowers from Toro, Husqvarna, Honda, Troy-Bilt, John Deere and Craftsman and others

Step 1: Confirm the engine is flooded

Step-by-step instructions for this step are being written.

Ignition path: magnet to spark: Flywheel magnet → Ignition coil → Stop / kill wire → Plug lead & boot → Spark plug → CombustionFlywheel magnetkey aligns timingIgnition coilair gap to flywheelStop / kill wiregrounds coilPlug lead & boottight fitSpark pluggap + conditionCombustionspark ignites mix
Ignition path: magnet to spark. Test the end of the chain first: a spark tester on the plug lead.

Step 2: Open the choke and throttle

Step-by-step instructions for this step are being written.

Primer and choke circuit: Fuel tank → Primer bulb → Return line → Carburetor → Choke plate → Run positionFuel tankpickup linePrimer bulbfills with fuel?Return lineback to tankCarburetorpriming portChoke plateclosed to startRun positionchoke open
Primer and choke circuit. A cracked primer bulb pushes air, not fuel. The choke must open once the engine fires.

Step 3: Remove and dry the spark plug

Step-by-step instructions for this step are being written.

Ignition path: magnet to spark: Flywheel magnet → Ignition coil → Stop / kill wire → Plug lead & boot → Spark plug → CombustionFlywheel magnetkey aligns timingIgnition coilair gap to flywheelStop / kill wiregrounds coilPlug lead & boottight fitSpark pluggap + conditionCombustionspark ignites mix
Ignition path: magnet to spark. Test the end of the chain first: a spark tester on the plug lead.

Step 4: Clear the cylinder and restart

Step-by-step instructions for this step are being written.

Ignition path: magnet to spark: Flywheel magnet → Ignition coil → Stop / kill wire → Plug lead & boot → Spark plug → CombustionFlywheel magnetkey aligns timingIgnition coilair gap to flywheelStop / kill wiregrounds coilPlug lead & boottight fitSpark pluggap + conditionCombustionspark ignites mix
Ignition path: magnet to spark. Test the end of the chain first: a spark tester on the plug lead.

Step 5: Check the float needle if it keeps flooding

Step-by-step instructions for this step are being written.

Inside a float-bowl carburetor: Fuel inlet → Needle & seat → Float → Float bowl → Main jet → Emulsion tube → Venturi / throttleFuel inletfrom tankNeedle & seatshuts off flowFloatsets fuel levelFloat bowldrain screwMain jettiny orificeEmulsion tubemixes airVenturi / throttleto intake
Inside a float-bowl carburetor. Varnish from old fuel usually blocks the main jet or emulsion tube first.

Brand notes

Brand-specific notes for Toro, Husqvarna, Honda and Troy-Bilt are being researched.

When to take it to a shop

Hand it over if the engine still will not run after the fuel, spark and air checks, if you find metal in the oil or the engine is seized, or if the machine is under warranty (opening it yourself can void it).

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Frequently asked questions

Answers being written: How do I know if my engine is flooded? · How long should I wait before restarting a flooded engine? · Why does my mower keep flooding? · Can over-priming flood an engine?