13 Reasons Your Craftsman Snowblower Won’t Start

There could be a lot of reasons your Craftsman snowblower won’t start. Or any snowblower for that matter. But if you look at the bigger picture, there’s really only 3 general things that could be wrong. By isolating the components, we can figure it out and fix it.

Tools Needed (Commissions Earned)

Any gasoline engine needs three things to run:

• spark
• air/fuel mix
• compression

Isolate the components that make those up and you can identify what’s at fault.

Testing For Spark

I like to start with checking for spark because it’s quick and easy to cross off. To determine if you have spark, simply remove the spark plug boot and connect a spark tester. One end fits on the spark plug terminal and the other connects to the spark plug boot.

Now, when you turn the machine over either by recoil or engaging the starter motor, if you have spark then the tester will light up. The brighter it is, the greater the spark.

This is a safer method than just holding the spark plug on the block, but you can do that too. Just remove the spark plug altogether and hold the electrode against the metal engine block.

When I say hold, I mean place. Don’t keep your hand on it because you will get shocked. If there’s no other way to do it but holding it, make sure to hold it only on the rubber parts.

Now when you turn the engine over, you should see a visible spark jump from the electrode to the block. It’s helpful to dim the lights for this as the spark can be hard to see in bright light.

If you’ve done either of the two tests, you now know if you have spark. If you do, then move on to testing the air/fuel mix. On the other hand, if you’ve determined that you don’t have spark, let’s fix that before we move on.

Fixing a No Spark

Now we’re getting a little deeper into the spark system. For this, there are a few different types of electrical systems that could be at fault. It depends on your machine, or more specifically, how old it is.

Spark Plug

I start with the spark plug because it’s the easiest to isolate and test. Just remove it and put try a good, working spare. I typically keep several spares of different sizes around for this purpose.

If you only have a couple of machines, then just keep some of those sizes on hand. You’ll eventually need one anyway.

Swap in a different spark plug and see if that alleviates the problem. If it doesn’t, move on to the lead.

Spark Plug Boot/Lead

The spark plug boot is the rubber connection that goes on the terminal of the spark plug. This then leads to the points/condenser or electronic ignition coil. Hence why it’s called the spark plug lead.

You’re assessing these components for damage. The lead often runs underneath some metal shrouds, so you might have to remove them to visually inspect the lead.

These shrouds can also sever the rubber jacket on the lead, or it can deteriorate over time. And, rodents have been known to feast on them as well.

Regardless of the cause, if the wiring inside the jacket is allowed to ground on anything metal, the spark system will ground out prior to the spark plug electrode and there will be no spark.

Points/Condenser

Older engines typically used a points and condenser electrical system. When functioning properly, this would open and close to create the spark. It would then travel through the spark plug lead and down to the spark plug electrode.

This system is notorious for going bad, especially if the machine has sat for several years. Fortunately, it’s easy to remedy.

Remove the flywheel and you’ll see the points cover underneath. Open that up and you will have access to the points. If you’re unsure what they look like two terminals that almost make contact when the engine turns over.

Or, just look for the whitish green corrosion that’s usually found on them. When this is present, the points cannot create a spark, so we need to clean that off.

To do so, grab a points file and carefully clean off the gunk. Be sure to blow it out with compressed air afterwards.

While you’re in here, make sure the points gap is set correctly. To do so, you’ll need to look up the gap spec for your engine. Manuals are handy!

Ignition Coil

The ignition coil performs the same function of the points/condenser. It’s the most common spark generating system used today.

Testing it is a two step process.

First, remove the small wire that goes to the kill switch on the ignition coil. It’s generally on the back side of the ignition coil.

With that removed, turn the engine over. If it now has spark and starts, you know that there’s a short to ground somewhere in the system and the coil is good.

A more thorough test involves the use of a multimeter and it’s easiest if you remove the coil from the machine.

It’s helpful to have the coil specs for your engine on hand, but not totally vital. Turn your multimeter to ohms at 20K. Then, connect one lead to the spark plug boot and the other to the metal base that bolts onto the block.

We want this resistance to (generally) be above 2k ohms. Since you’ve set the multimeter to 20k, it will show as 2.

Then, test with one lead on the grounding base and the other lead on the kill switch. This should again (generally) be above 2k.

Last, test with one lead on the kill switch and the other on the spark plug boot. This test should read a bit higher, (generally) above 10k.

If any of these tests are way low, then you know the coil needs to be replaced. Again, it’s very helpful to find the exact specs for your machine.

Timing

The last component of the electrical system is the timing via the flywheel. The flywheel has magnets on it that essentially activate the coil to produce spark. Obviously, they need to fire at the right time.

In order to keep time, the flywheel is keyed into the correct position by a metal key. This connects it to the crankshaft so that the magnets pass the coil correctly.

To ensure correct timing, several things need to be present. First, the key. Without it, timing is off. Pop the flywheel off and you can see if the key has sheared off or is missing.

Secondly, the magnets on the flywheel need to be clean. If they’ve rusted over, that can prevent the coil from firing.

Last, the correct gap has to be set for the coil. This is the space between the coil and the flywheel. The easiest way to set the gap is to use a standard business card.

Loosen the bolts that mount the coil to the block and it can slide up and down. Insert a business card between the coil and the flywheel. Then, rotate the flywheel until the magnets are aligned under the coil.

The magnets will pull the flywheel down onto the business card, and the correct gap will be set. Tighten the coil down and remove the card.

Testing the Air/Fuel Mix Components

Engines need fuel right? We all know that. So now that we’ve taken care of the spark let’s move on to the fuel system.

Fuel Tank

There’s gas in there, right? It seems obvious, but you’d be surprised how often this happens. Moreover, what’s the condition of the gas in there? How dirty is it? How old? If it’s suspect, drain it out and replace with fresh fuel. Assess the condition of the tank; if dirty, clean it. If rusty, try a rust converter.

Fuel Filter

This is a consumable item dictated by the engine manufacturer. The filter “filters” sediment from reaching the engine. So yeah, it’s kind of important. That being said, a lot of snowblowers don’t have fuel filters. I like to add one to my machines for a bit extra peace of mind.

These filters get gelled up with old fuel and that can restrict passage of gas to the engine. If there is a filter and it’s suspect, replace or remove it for further testing.

Carburetor

Ah, the notorious carburetor. Don’t worry, it’s not as scary as it sounds. The carburetor mixes the air and fuel that enters the combustion chamber to the right proportion.

If the jets inside the carburetor are dirty, then there won’t be enough fuel, so the mixture will be too lean. Dirty fuel and/or gelled fuel can restrict the jets, so it’s important to keep a carburetor clean.

You can remove the float bowl on the bottom of the carburetor to assess the condition. If the bowl is dirty, then you can be assured that the jets are dirty as well. In that case, I like to remove the carburetor entirely to soak the individual parts in an ultrasonic cleaner.

Take photos as you remove parts and it will be easier to put back together. Depending on the carb you have, there can be multiple jets. Remove all you find and disassemble as much as you can. This will ensure the best cleaning.

It’s helpful to purchase a “carb kit” for your engine. They’re usually around $15-20 and come with replacement parts for the carburetor. I like to replace all of the gaskets with new ones after a thorough cleaning.

Once the carburetor is back on the machine we can be assured that we’ve done our diligence on the fuel system. It is possible that no matter how much you clean the carb it still isn’t working.

There are passages inside the carb that you just really don’t have access to. If those are plugged, then really no amount of cleaning will help and it’s best to just replace the carb.

So, if it doesn’t work then clean it a few more times and once you’re ready to quit then just buy a new one.

Testing For Compression

Now that we’ve ensured spark and the correct air/fuel mix, we can move on to testing the compression.

I test for compression last because it generally isn’t the problem. It’s usually like 70% fuel issues, 20% spark issues, and 10% compression.

Luckily, it’s super easy to test for compression. Simply remove the spark plug and insert the threaded end of the compression tester. Turn the machine over and it will register how much pressure or compression is in the combustion chamber.

For small engines, around 80-90 psi should be sufficient. If you’re down around 30 or possibly less, then it needs to be fixed.

A little trick you can try before tearing the engine apart is to dribble a little bit of oil into the spark plug. This oil can fill the gap between the piston rings and the cylinder wall. If the loss of compression is due to scored walls or stuck piston rings, the oil will replicate their function.

Now you can redo the compression test and see if the compression has increased. If so, you know the problem lies with stuck rings or the cylinder walls. Since the compression has increased, you can possibly start the engine now.

In the event that it starts, it’s possible that the heat of running will break the rings free and they’ll do their job again. It very well could solve the problem. 

But, it’s unlikely. More often than not, I end up having to disassemble the engine in order to assess compression issues. Before I do so, I like to use a borescope to assess the cylinder walls.

The borescope is placed into the spark plug hole so I can see the condition the cylinder walls are in.

If it turns out that the walls are really scored then I know the engine probably isn’t salvageable, and it’s not really worth the effort to disassemble.

However, if the walls are decent, then I know we can rebuild it.

Other Losses of Compression

Compression can be lost through a blown head gasket, stuck or worn piston rings, stuck valves, a dropped seat, or even a broken connecting arm.

The only way to know is to remove the cylinder head. This is easy to do, just remove the bolts that hold the head on. Pay attention to which ones go where because sometimes they’re not all the same length.

Once the head is off, you should be able to tell what the problem is. If the piston doesn’t move when you rotate the crankshaft, you know it’s likely the connecting arm. You’ll need to fully disassemble the engine in order to replace it.

More common is a stuck valve or dropped seat. Since we’ve already done the work to access the cylinder, I like to spend a bit of time cleaning everything while I’m in there.

Remove the valves and give them a good cleaning with a brass wire wheel. Clean the piston, cylinder walls and head in the same fashion. Only use brass though; since most cylinders and heads are made of aluminum, they can score easily.

The seat is the mating component for the valve; it’s where the valve “seats” to the engine block. They can fall out, and that’s called a “dropped seat.” This can happen when the engine overheats.

Just clean it and put it back into place. Then, take a punch and smack some divots into the block all the way around the seat. This helps to push the aluminum material out into the seat for some extra compression to hold it in place.

Best case scenario is that it’s just a head gasket, and you can simply replace it.

Recap

So while there may only be 3 general reasons why your Craftsman snowblower won’t start, as you can see there are quite a few underlying reasons. It’s easy to get overwhelmed if you think about all the possibilities, so just try to have a systemized plan. Isolate the components and check them off. After you’ve done it a few times, you’ll have no problem diagnosing the issue.

Did I forget something? Let me know in the comments below!

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