Snowblower Won't Start No Spark

Snowblowers live a tough life, or do they? When you think about it, they spend more than half the year sitting idle, and that’s often the root cause of no spark. I’m a mechanic and snowblower no spark is one of the more common complaints I hear, for most the fix is simple.

The most common cause of a snowblower without spark, is a fouled spark plug. Cleaning and gapping or replacing the spark plug will fix the problem. Other likely causes of snowblower no spark, include:

  • Faulty control switch (on/off switch)
  • Failed armature

In this post you’ll learn how to diagnose and fix the top three causes of a snowblower with no spark. You’ll learn how to clean and gap a plug, check spark, test the control switch and test & replace the armature.

Mower gas cap

Vented Gas Cap

Testing Snowblower Spark

I know you tested the spark plug and found no spark, but it’s worth noting testing for spark without a test tool is sometimes hit and miss, especially if you are testing solo.

Viewing the plug while yanking on the cord can be tricky and you know if the plug doesn’t ground it won’t spark.

I recommend using a spark test tool, the tool does a better job than a spark plug as it stresses the armature, causing it to work extra hard to fire the tool. In a test situation, this is exactly what we want. You can find the test tool I use here on the “Small engine tools page”.

Mower gas tank

Winged & Threaded caps

Diagnosing No Spark

In this section I will show you how I test for spark, both with and without a spark test tool. You’ll need a few basic tools, they include:

  • Insulated pliers (plastic coated handle)
  • Plug tool or ratchet & plug socket
  • New plug
  • Helper
  • Spark test tool (optional)
Vented mower gas caps

Vented gas caps

Testing without test tool

To nail this successfully, a helper and a new spark plug are advised.

Follow these steps:

  • Remove the spark plug wire (twist and pull)
  • Remove the spark plug
  • Reattach the spark plug wire to the now loose plug
  • Using a insulate pliers, ground and hold the plug against the engine
  • Have the helper perform the start sequence (crank engine)
  • View plug tip for spark
  • Repeat with new spark plug

If neither plug fires, suspect a faulty armature (coil). A faulty control switch is possible and so should be eliminated before condemning the armature.

Testing with test tool

Obviously a test tool is required and a helper would be nice.

Follow these steps:

  • Remove the spark plug wire (twist and pull)
  • Remove the spark plug
  • Attach the spark plug wire to the spark test tool
  • Ground the test tool
  • Have the helper perform the start sequence (crank engine)
  • View test tool window for spark

As before, if no spark present, suspect a faulty armature (coil). A faulty control switch is possible but less likely, in any event it should be eliminated before condemning the armature.

This is covered below.

Cleaning & Gapping Spark Plug

Spark plugs have a difficult job, a combustion chamber is a pretty hostile environment. A plug needs to operate at a sufficiently hot temperature so as to burn off contaminants and yet not so hot that it ignites the fuel mixtures prematurely.

Although spark plugs all look identical they are optimized for particular temperatures, each type plug is coded and that code indicates a special set of parameters including it’s optimal operating temperature.

This is a long winded way of saying, plug type is super important. Fitting the wrong plug can cause all sorts of problems.

Just some include:

  • Hard starting issues
  • Hot starting issues
  • Flooding
  • Rough idle
  • Lack of power
  • Misfiring
  • Surging
  • Black smoke
  • Plug fouling
  • Burning plugs

I never assume the plug type I remove is the correct type, I go and check in the operating manual.

Spark Plug Cleaning

Plug build up at the electrode happens, however it really shouldn’t. As said earlier, a plug that collects sooty or oily deposits on the tip could suggest the wrong plug type fitted. It could also indicate other problems, common among them include:

  • Bad gas
  • Dirty air filter
  • Bad carburetor
  • Too much oil added
  • Worn out engine

Cleaning a plug is easy.

A wire brush is the best way to approach it.

    After cleaning the carbon, or oily deposits, electrical contact cleaner works to remove oily residue. Alternatively, use a hot flame to burn off the oil.

    That’s it, it’s clean. But before fitting it makes sense to check and adjust the gap. That’s what we’ll do next.

    Gapping Spark Plug

    Gapping the plug is as it’s name suggests, checking the gap in the electrode. The wider the gap the stronger the spark and the harder the armature has to work to jump the gap. As we said earlier each plug type has a particular gap size. It is important as it is paired with the engine’s electrical system.

    A gap that’s too big may cause misfiring and premature armature failure. A gap that’s too small on the other hand could cause a weak or no spark, constant plug fouling, no starts, temperamental starting, flooding and the list goes on.

    A spark plug gapping tool is an inexpensive measuring (inches and mm) tool worth having in the tool box.

    All the common sizes are marked clearly on the tool and it’s simply a matter of checking the gap size for your plug type and adjusting the plug gap by either opening the gap (use pliers or tool) or closing the gap (by tapping) until the tool fits snugly between the electrodes.

    Not anymore complicated than that.

    Testing Snowblower Control Switch

    The snowblower control switch is basically the on off switch. They are pretty basic and as a result rarely cause problems.

    How does switch work?

    The story begins with the switch in the on position. The armature is where voltage is produced and that voltage is constantly in search of the shortest and easiest path to ground. The plug offers a path to ground but because of the gap, it’s not perfect. It must jump the electrode to find ground and in doing so creates a spark, great!

    Now the switch is in the off position. This offers the armature a much shorter, easier path to ground. The armature takes the shorter path and so voltage is directed away from the spark plug and so it stops firing and the engine stalls.

    So it’s a basic system with few moving parts and little to go wrong. That said, chafing caused by a rubbed through wire or rodent damage can cause the wiring to ground and as you know that will offer the armature the short cut.

    Checking the wiring for signs of damage or use a DVOM to check continuity when the switch is in the on position.

    Place the meter on Ohms and place one test lead on the armature side of the switch and the second probe on ground. With the switch set to “Run” or “On” the meter should read “OL” (open). If you get a reading other than open, the circuit is shorting to ground.

    An easier way to test the wiring is by elimination, removing the armature wire and testing for spark will indicate either an issue with the armature or the wiring and we’ll cover that next.

    Testing Snowblower Armature

    To test the armature, the resistance of the internal coils could be measured, but I prefer to test it the old school way.

    The easiest way is to remove the ground control wire. The control wire offers a ground to the armature and by disconnecting it, we eliminate the possibility of a wiring issue.

    Armatures are solid state units, they can’t be repaired. So testing in this way removes all the variables from the equation.

    Many engine manufacturers place a quick connect wiring terminal by the side of the engine. Disconnecting isolated the armature. If your motor doesn’t have it, you’ll need to remove the blower cover to access the armature wire.

    The process is as  follows:

    • Remove the pull starter assembly
    • Remove the blower housing (cover)
    • Remove armature control wire

    Now reassemble and check for spark as before. If you now have spark, you’ll need to go back and check the wiring circuit, there’s a short to ground.

    However, the more likely outcome is still no spark – go ahead and replace the armature, it’s faulty.

    Replacing The Armature

    Replacing the armature isn’t a difficult job, and for most it won’t take more than one hour. No special tools needed, however a feeler gauge would be a great asset and if you choose to use the feeler gauge, you’ll need to check the armature air gap spec.

    Tools you’ll need:

    • Feeler gauge (optional)
    • Ratchet set
    • Screwdriver set
    • Wrench set

    The following is a stepped process, your steps may differ slightly as although snowblower engines are similar they aren’t identical.

    Removing the armature:

    • Remove the pull starter assembly
    • Remove the blower housing (cover)
    • Remove plug wire
    • Remove armature control wire
    • Remove the armature fasteners (2)
    • Remove the armature

    Fitting the armature:

    • Fit new armature in place and loosely fit bolts
    • Fit feeler gauge between the armature and the flywheel (mechanics hack – use a business card instead, approx. correct)
    • Pushing the armature firmly against the flywheel, tighten the fasteners
    • Remove the feeler gauge (business card)
    • Fit the armature control wire

    That’s it, reassemble in reverse order. Nice work you!

    Share

    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.