« Pen Sculpture by beamcarver | Main | Oil Changes - Suck It Up »

November 17, 2010

Changing a Lawnmower Spark Plug

Spark My Words
Diagnosing and changing your lawnmower spark plug

I wouldn’t have known this until yesterday, but if you want the feeling of empowerment without actually doing anything remarkable, look no farther than your lawnmower’s spark plug.

Spark plugs are the heartbeat of a nice lawn.  Without a rhythmic pulse of sparks zapping the mixture of gas and air in your carburetor, the engine starts sounding like it has croup and unceremoniously dies.

You’ll try restarting it and it might seem to be fine for a few minutes and then, again, it dies faster than your commitment to that fitness regimen your doctor prescribed. 

With concern, you check the gas and oil levels, and even the air filter.  You restart the engine again.  It strangles and conks out.

Now your tailbone curls up with a prickle of primal fear.  Because this could take a while to fix, and your lawn is now sporting a mullet (short at the front, long at the back).

This is the fork in the road, the choice between despair and hope that will probably involve several trips to Canadian Tire.

This is the moment when you forego consulting the Yellow Pages for a small engine repair person and take one small step that’ll give you a week’s worth of conversational nuggets in the line-up at Tim Horton’s.

This is your chance to prove your competency to skeptical neighbours watching from their front porches.  Let them smirk.  Smirk back, and even give them a casual little wave like you were expecting this.

And whatever you do, don’t move the lawnmower to the garage.  That would be admitting defeat.  You want to leave that thing right where it is, while confidently sallying inside to pick up a socket wrench or a spark plug wrench if you have one.  Or just a whole armful of wrenches, which will give you the look of an intrepid adventurer.  Sometimes it’s all in the look.

Return to the stranded mower and remove the rubber cap covering the top of the spark plug, which is recessed enough that it requires a socket with a long hexagonal shaft to fit over the entire plug so that you can twist it out at the root.

Crank to the left to loosen the spark plug.  It’s likely to be in there pretty tight especially if it’s never been changed in the known history of the lawnmower.

When it’s loose, use your fingers to finish unscrewing it. Next, de-smudge the ceramic mid-section of the spark plug with your finger to reveal the string of letters and numbers that identifies the exact model of your plug. 

Drop the spark plug casually into your pocket and head off to Canadian Tire.  The spark plug aisle will assail you with all 978 configurations of spark plugs.  According to Ruffman’s Law of Inventory, your spark plug will not be there. 

Don’t substitute for one with similar letters, no matter how close they are.  Spark plugs are fussier than a cat whose water dish hasn’t been topped up in the last half hour. 

Turn to the nice lady at the parts counter.  She will have your spark plug model hidden in that secret room behind the tires.

Next, pick up a gapping tool – known laughingly in immature circles as a ‘feeler gauge’.  There are about 20 models of feeler gauges, each capable of measuring different ranges of electrode gaps (the tiny space between the sturdy little wire electrode and the spark plug).  Choose a gauge that offers the correct gap (specified in your manual).  TIP:  Most spark plugs come pre-gapped by the manufacturer nowadays, but it doesn’t hurt to confirm with a feeler-gauge.

When you get home, return confidently to the mower. Install the new spark plug carefully, rotating it counter-clockwise a couple of times to seat it properly, then turning it by hand to avoid cross threading. 

Once it’s all the way in, tighten it one half-turn with your wrench to compress the washer.  Replace the rubber cap over the tip of the spark plug. 

Start that baby up.  Notice the smoother engine sound.  Strut around your lawn while the neighbours applaud.  Acknowledge your triumph by going from porch to porch accepting compliments and beer.


The comments to this entry are closed.


  • Get ToolGirl's Newsletter
  • Watch ToolGirl's videos


  • Flickr
  • Twitter
  • Facebook
  • Pinterest

Mag's Books

  • : We're All In This Together

    We're All In This Together
    Based on four years of interviews with Steve Smith, Mag's unconventional biography reveals the personal stories, sorrows and joys that continue to inspire the man behind the Red Green legacy.

  • : How Hard Can It Be?

    How Hard Can It Be?
    Mag's quirky and entertaining book of home improvement projects for beginners.

Nota Bene

  • It’s never too late to be who you might have been. - George Eliot (1819-1880)
  • Simplicity of character is the natural result of profound thought. - My fortune cookie