By: Author John Cunningham. Published: 2021/06/16 at 11:02 am
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.
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. It will need to be checked, cleaned, and gapped correctly.
I’ve got you covered; we’ll do all of that in this post.
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.
Checking Snowblower Plug Code
While spark plugs may look identical, they are in fact different. Plugs are grouped broadly by heat range, reach, and thread size. A code stamped on the plug insulator identifies the plug type.
Thread size is self-explanatory; it’s the diameter of the plug threads that 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 contaminants 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 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 are 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 the 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. It often gives you a heads-up on an underlying issue.
Here’s a list of plug electrode conditions and what they likely mean:
- Tan/grey color – operating as normal.
- Dry black soot – engine running rich. Common causes include restricted airflow, bad gas, carb mix too rich, choke stuck, ignition system fault.
- White – engine running lean. Common causes include carburetor issues, incorrect gas, overheating engine, ignition fault.
- Wet & oily – too much oil in the engine, breather issue, head gasket failure, worn rings.
- Blistered insulator – ignition system issue, wrong plug type, overheating 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 textbook 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
The service manual way: This calls 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 toolbox.
See the video here on checking the spark plug spark.
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
You may find the following post helpful – How ignition systems work?
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 contaminants.
See the video here on cleaning the spark plug.
The process is as follows:
Use contact cleaner or deglaze with a naked flame to remove contaminates
Using a wire brush, clean soot deposits from the electrodes and wipe with a 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 gauges. You’ll also need the spec for your spark plug. Common gap specs include .020″ – .030″.
Check out the video here on gapping a spark plug.
Follow these steps to gap a spark plug:
- Remove plug
- Clean plug
Check plug spec in the owner’s manual – Typically .030″
Check plug gap
Adjust the electrode as per findings, to close the gap – tap on the electrode.
To open the gap pry on the electrode.
Fitting Snowblower Plug Correctly
What can go wrong with fitting a plug, you might well ask. The truth is a lot can go wrong. Snowblower engines are made from aluminum, and the cylinder head threads are soft. Accidentally cross-threading spark plugs are easily done unless you follow a 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 ideally be torqued to specification.
Torque 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 a torque wrench is as follows:
Thread the plug by hand until seated (do not use the ratchet)
When seated, use a torque wrench to tighten the 14 mm plug (common) to 14.75 ft-lbs. (20Nm).
See the video here on setting a torque wrench.
No torque wrench? No problem, I’ll show you a mechanic’s hack.
Fitting without torque wrench is as follows:
New plug on the left with crush washer intact. Used plug on the right with compressed crush washer.
- Thread the plug by hand until seated (do not use the ratchet)
If the plug is a new plug (never previously fitted) – when seated, use socket and ratchet to tighten the new plug a 1/4 turn (quarter turn).
Used plug (the plug was previously fitted) – when seated tighten 1/8 turn (one-eighth turn)
- About the Author
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John Cunningham is an Automotive Technician and writer at Lawnmowerfixed.com.
He’s been a mechanic for over twenty-five years and shares his know-how and hands-on experience in our DIY repair guides.
Johns’s How-to guides help homeowners fix lawnmowers, tractor mowers, chainsaws, leaf blowers, power washers, generators, snow blowers, and more.