How Often To Change Snowblower Spark Plug ?

Spark plugs have it tough, they must withstand voltage spikes, extreme heat, pressure and chemicals, all without skipping a beat. Pretty impressive!

Snowblower spark plugs should be changed every second season or every Two hundred hours of operation, whichever comes first.

In this post you’ll learn the importance of a spark plug. You’ll learn how to remove it, check plug type, check spark, clean it, gap it and how to refit it correctly.

Mower gas cap

Vented Gas Cap

the importance of a spark plug

I can’t tell you how many small engines I’ve fixed by simply changing the spark plug.

While spark plugs don’t outright fail very often, they do cause problems. Common issues include fouling and poor gapping and we’ll look at both of these a little later.

A spark plug is typically changed in a small engine once a year.

However, as snow blowers generally work for only a few months of the year, the spark plugs only need to be changed every second year.

The plug will need some maintenance every year though, it will need to be checked, cleaned and gapped correctly. I’ve got you covered, we’ll do exactly that right now.

Vented mower gas caps

Vented gas caps

removing spark plug

Removing the spark plug will require a ratchet and deep socket also known as a plug socket. The procedure is simple and if you’ve done this before you can likely skip this section. The removal process is as follows.

  • Locate plug wire
  • Remove plug wire (twist & pull)
  • Using the ratchet and socket turn the plug counterclockwise to loosen
  • Remove spark plug

Checking Snowblower Plug code

While spark plugs may look identical, they are infract different. Plugs are grouped broadly by heat range, reach and thread size. A code stamped on the plug insulator identifies plug type.

Thread size is self explanatory, it’s the diameter of the plug threads which obviously must match that of the engine.

Reach is simply how far the plug threads into the combustion chamber or thread length.

Heat range is however a little more interesting. A plug is designed to get just hot enough to burn off contaminates that naturally occur inside the combustion chamber, (oil & carbon) however the plug shouldn’t get so hot that it ignites the fuel mix before firing the plug.

It’s a balancing act and your snowblower engine maker has tested and fitted the optimum heat range plug.

Problems commonly arise when the incorrect plug is fitted. Not too many will be caught out by the thread diameter or length, but fitting the wrong heat range is more than possible is very common.

Symptoms of incorrect plug type

Symptoms of incorrect heat range plug are numerous, they really do cover a wide selection of complaints. Here’s just a few of the common ones:

  • No start Stalling
  • No power
  • Starts then stops
  • Surging idle
  • Stops when hot
  • Won’t restart
  • Constant plug fouling
  • Flooding
  • Black smoke
  • Sputtering

I never assume the plug I remove is the correct code, I’ll check the code against manufacturers specs. I’ve been caught out before chasing a problem that didn’t exist and I’ve learned my lesson. I’m passing it on.

Checking Snowblower Plug Condition

After removing a spark plug it’s worth checking the color of the electrode. The color can tell a ton about what’s going on inside your snowblower engine. If often gives you the heads up on an underlaying issue.

Here’s a list of plug electrode conditions and what they likely mean:

  • Tan/grey color – operating as normal
  • Dry back soot – engine running rich. Common causes include restricted air flow, bad gas, carb mix too rich, choke stuck, ignition system fault
  • White – engine running lean. Common causes include carburetor issue, incorrect gas, overheating engine, ignition fault
  • Wet & oily – too much oil in engine, breather issue, heat gasket failure, worn rings
  • Blistered insulator – ignition system issue, wrong plug type, over heating engine, E15 gas

Checking Snowblower Spark

Every engine needs compression, fuel and spark. Checking spark is one of the go to tests every self respecting DIY mechanic needs to know.

You may already know how to test for spark, if so good job, if not buckle up. I’ll show you two ways to test the MacGyver way and the text book way.

The MacGyver way: This works fine for most situations, however if you have a temperamental no start issue, this way may not stress the ignition sufficiently to reproduce the fault. Anyway here’s the no tools MacGyver way.

  • Remove the plug wire (twist & pull)
  • Remove spark plug
  • Reattach the plug wire to the plug
  • Ground and hold the spark plug threads on the engine casting (use insulated pliers) Have helper attempt the start process
  • Check spark plug for sharp blue spark

The service manual way: This call for an ignition spark test tool. This tool as said stresses the whole ignition system and helps identify any faults.

This test is performed without removing the plug. This tool isn’t expensive and is worth having in the tool box. You can find the one I use here on the “Snowblower maintenance tools page” To use a spark test tool follow these steps:

  • Remove spark plug wire (twist & pull)
  • Attach the plug wire to the test tool
  • Ground the test tool on the plug
  • Have helper attempt the start process
  • Check tool window for sharp blue spark

Cleaning Snowblower Plug

As  part of your annual snowblower maintenance the plug will need to be removed and cleaned. Cleaning is a simple process, electrical contact cleaner works great but it’s not necessary. You will need a wire brush and a naked flame works great for burning off contaminates. The process is as follows: 

  • Use contact cleaner or glaze with naked flame to remove contaminates
  • Using wire brush, clean soot deposits from the electrodes
  • Wipe with clean dry cloth

Gapping Snowblower Plug

Gapping the plug is a simple process also. The spark plug electrodes, located at the tip must be set to the correct size gap. The plug gap changes slightly over time Compression and heating cycles tend to close the gap.

A plug gap that’s too small results in a weak inconsistent spark. A plug gap that’s too big may result in a no start, misfiring, hot start issues and premature armature failure.

As your snowblower is only a single cylinder, it can’t afford a misfiring plug.

To nail this procedure correctly you’ll need a gapper tool or a set of feeler gauge. You’ll also need the spec for your spark plug. Common gap sizes include .020″ – .030″.

Follow these steps to gap a spark plug: Remove plug Clean plug

Follow these steps to gap a spark plug:

  • Remove plug
  • Clean plug
  • Check plug spec
  • Check plug gap
  • Adjust the electrode by closing or opening as per gapping tool

Fitting Snowblower Plug Correctly

What can go wrong fitting a plug you might well ask. Truth is a lot can go wrong. Snowblower engines are made from aluminum and the cylinder head threads are soft.

Accidently cross threading spark plugs are easily done unless you follow simple procedure. Cross threading can be repaired but truthfully it’s a pain in the ass, better to avoid such problems.

In addition, a spark plug should be ideally be torqued to specification.

Torqueing to specification prevents overtightening which often results in stripped threads or loose plugs which can also result in damaged threads. If you want to go by the book you’ll need a torque wrench, you’ll find the wrench I use here on the “Snowblower maintenance tools page”.

Fitting with torque wrench, is as follows:

  • Thread the plug by hand until seated (do not use tool)
  • When seated, use torque wrench to tighten 14 mm plug (common) to 22 ft. lbs. (30Nm). 

Don’t fancy a torque wrench? No problem, I’ll show you a mechanics hack.

Fitting without torque wrench, is as follows:

  • Thread the plug by hand until seated (do not use tool)
  • New plug – when seated, use tool to tighten new plug one half turn
  • Used plug – when seated tighten one quarter turn

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Auto Technician and Writer at Lawnmowerfixed | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.