Lawn Mower Engine Won’t Start

July 11, 2011



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It is the height of the hot summer season and your lawn mower engine won’t start.

What should you do?

  • The first thing you should check is the fuel. 2-cycle lawn mower engines require the proper mix of 2-cycle oil and gasoline. Shake the mix to blend completely. Always use fresh fuel, never stuff that is old, leftover or has been sitting around for a long time. Fuel should always be stored in an airtight container in a cool, dry place, away from sparks and flame. All vents on the can should be tightly closed. Bad gas, especially at the start of the season (but this could happen any time) is one of the most common reasons your lawn mower might be refusing to start.
Lawn Mower Engine Oil

Lawn Mower Engine Oil

  • If  your lawn mower has a 4-cycle engine, be sure to use the right type of engine oil. Also, check that the oil is clean, and is poured into the machine at the proper level.
  • Inspect your lawn mower and confirm that the ignition switch is turned on and the transmission in neutral. All attachments should be  disengaged. Consult your owner’s manual for starting procedures for your lawn mower (if you are in doubt at all) as most machines have safety mechanisms that will not allow them to start unless they are correctly followed.
Manuals for most types and brands of lawn mower engines

Manuals for most types and brands of lawn mower engines

  • Examine the spark plug on your lawn mower engine. First, make sure that there is no spilled gasoline anywhere near your machine, then spin the engine by pulling the rope or turning the key. A blue spark jump across the plug gap should appear. If this happens, your lawn mower engine should start without trouble.
Small Engine Spark Plugs

Small Engine Spark Plugs

  • If the spark emerging from your spark plug is not blue but yellow and weak (or there is no spark at all)  then you know that you need to replace the spark plug on your machine. Cleaning the old spark plug doesn’t really work.
  • If the spark is new and your machine still won’t start, check to make sure that fresh gasoline is getting to the carburetor.  Check that the fuel shutoff valve is open, and that the fuel line is not plugged or buckled. The fuel cap vent should be open and all tank screens clear of dirt and garden debris. Inspect all mounting screws and bolts to make sure that they are snug and gaskets are not missing. If you need a carburetor kit replacement, it is easy to install a new carburetor kit yourself.
Carburetor Rebuild Kits

Carburetor Rebuild Kits

Happy mowing!

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