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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
Cause 1: Blocked fuel cap vent
Step-by-step instructions for this cause are being written.
Fuel path: tank to cylinder. Fuel must flow through every stage. A blockage at any box starves the engine.
Cause 2: Partly clogged carburetor jet
Step-by-step instructions for this cause are being written.
Inside a float-bowl carburetor. Varnish from old fuel usually blocks the main jet or emulsion tube first.
Cause 3: Restricted fuel filter or line
Step-by-step instructions for this cause are being written.
Fuel path: tank to cylinder. Fuel must flow through every stage. A blockage at any box starves the engine.
Cause 4: Dirty air filter
Step-by-step instructions for this cause are being written.
Air intake path. A restricted filter richens the mixture; a leak after the carburetor leans it out.
Cause 5: Water or old fuel in the tank
Step-by-step instructions for this cause are being written.
Fuel path: tank to cylinder. Fuel must flow through every stage. A blockage at any box starves the engine.
Cause 6: Ignition coil failing when hot
Step-by-step instructions for this cause are being written.
Ignition path: magnet to spark. Test the end of the chain first: a spark tester on the plug lead.
Which cause is it?
The decision table is being compiled from shop pricing and manufacturer data.
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).
Find a lawn mower repair shop near you
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Answers being written: Why does my mower die when it gets hot? · Can a gas cap make a mower stall? · Is it the carburetor if my mower starts then dies? · How much does a carburetor cleaning cost at a shop?