What to do if your lawn mower won’t start

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When you dust off your mower, push it into the springtime sun, you can nearly smell the freshly-mowed lawn. But if you’re like us, every once and a while, you’ll find that the engine won’t start.

If your lawn mower won’t start, the first thing I’d do is use an ignition/spark tester.

As the owner and operator of a residential and commercial landscaping care business for 25+ years, an ignition/spark tester was my go-to tool if an engine failed to start. With an easy-to-read terminal screen, this tester helps you troubleshoot and determine the most likely cause of the equipment’s failure to start such as a dead spark plug, a bad ignition coil or something else. It will save you a lot of time.

RepairClinic has free troubleshooting and repair help information for this lawn mower problem and many others.

The most likely cause of a lawn mower engine not starting

There are many causes for engine failure but by far, the most common cause is a faulty spark plug.

Fortunately, replacing a spark plug is simple.

Always read your lawn mower’s owner manual’s instructions for spark plug replacement. Be sure to use the exact spark plug recommended for your engine. Using an alternative spark plug can cause serious engine problems.

Here’s how to replace a lawn mower engine spark plug:

  1. Make sure the engine is cool.
  2. Remove the wire and boot from the spark plug.
  3. Use a spark plug wrench to remove the old spark plug.
  4. Install the new spark plug with care by tightening it onto the cylinder head. Be careful not to over tighten or damage the plug.
  5. Attach the spark plug wire and boot.

This Spark Plug Wrench (#1644997) enables you to more safely and efficiently remove or tighten a spark plug. We often give this tool as gifts to family and friends, as it comes in handy for anyone who owns a lawn mower, snowblower or other small engine. Check out our other favorite tools for DIYers.

Here’s our helpful video on how to use a spark plug wrench:

How to avoid engine failure in the future

Replace the spark plug at least once per season, even if it appears to be working. Over time, a spark plug’s performance will degrade due to carbon build-up and a weakened electrode. This dramatically increases emissions, reduces engine performance and requires the engine to use more fuel.

Engine tune-up kitEvery spring, I purchase tune-up kits packed with a spark plug, oil, filter, fuel stabilizer and other essential maintenance products as recommended by the manufacturers specifically for my engine models. It takes the hassle out of looking up each individual product.

A spring engine tune-up will improve engine performance, reduce emissions and extend the life of equipment. Save yourself the hassle of finding tune-up essentials like motor oil, air filters, spark plug and fuel stabilizer individually. A tune-up kit designed for your engine includes everything you need. Enter your engine model number at https://www.repairclinic.com/Shop-For-Parts/a21c114/Lawn-Mower-Tune-Up-Maintenance-Kit-Parts to find the kit designed specifically for your model. All tune-up kits are on sale through May 31, 2013.

Other helpful information

7 simple ways to make lawn mowers run like new

11 easy, money-saving steps to prep your snowblower for storage

Lawn mower maintenance tips

How a lawn mower works

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