Why Won’t My Snowmobile Start?


Whether your snowmobile uses an electronic start or even a classic pull cord, when you go to turn on the ignition and nothing happens, it’s scary. You give your sled’s ignition another try and nothing. What is going on and why won’t your snowmobile start?

Your snowmobile might not start for these reasons:

  • Altitude changes
  • Damaged head gasket
  • Broken/worn cylinder parts 
  • Low cylinder compression
  • Dead spark plugs
  • Fuel line blockages or the line dried out
  • Leftover old gas in the tank 

As you might have assumed, there is a lot that could be going on behind the scenes that’s preventing your snowmobile from starting. Ahead, we’ll talk about each of the above issues in more detail so you can diagnose your sled and get it running again. 

8 Reasons Your Snowmobile Won’t Start

You Changed Your Altitude

If you own a mountain snowmobile in particular, you’re used to scaling ascending altitudes on your snowmobiling treks. Yet the next time you start at too high an altitude, you might notice that your sled doesn’t want to turn on. 

It’s always best if you’re at ground level or close to it when starting your snowmobile. Otherwise, changing from one altitude to another between now and the last time you used your sled can fail to get it started. By adjusting your engine settings to the higher altitude, this issue is easily fixable. 

Damaged Head Gasket

The gaskets in your cylinder deserve a little of your attention, especially the head gasket. This gasket separates the cylinder head and the engine block if your snowmobile has an internal combustion engine, which is overwhelmingly common. 

The head gasket also prevents engine oil and coolant from leaking from your engine to the cylinders. More importantly, this gasket maintains cylinder compression by creating a seal. We’ll touch on why cylinder compression is such a big deal later in this article, so keep reading. 

If your snowmobile’s head gasket is done for, you’ll be able to tell in a variety of disturbing ways. Your snowmobile will overheat more often as the combustible gases and coolant mix regularly. Any lubricant you add to your sled’s internal components will erode fast because the head gasket seals are broken.

The engine can get flooded with oil, which is about the worst-case scenario. You’d then have to buy a new engine, which would put a major hurting on your wallet. The catalytic converter can also end up wrecked through a bad head gasket.

Gaskets, like any part of your snowmobile, can wear down with time or misuse. The longer your sled’s head gasket goes without a repair and ideally a replacement, the worse the outcome for your snowmobile. 

Broken or Worn Cylinder Parts

If you thought that was the end of your cylinder worries, sorry to say, but we’re just getting started. A whole handful of cylinder parts can degrade or fail, all preventing your snowmobile from starting. These are the reed valve, crank seal, and piston rings. Let’s cover each component in more detail now.

A reed valve is a check valve that knows when fluid is entering, where it’s coming from, and how much fluid should pass through the cylinders. Depending on whether you need more fluid or less, the reed valve can open or close as appropriate. The pressure changes as well.

Admittedly, reed valves are pretty hardy, as they’re often made of carbon fiber or fiberglass. That doesn’t mean your snowmobile’s reed valve is forever. When it stops working, fluids can flood the cylinder and even the engine, causing some of the issues we discussed in the last section.

The crank seals of your cylinders can also malfunction. Crankshaft seals at the front of the sled’s engine maintain the flow of oil the crankshaft relies on, keeping the oil in the crankcase. If oil leaks, it can accumulate around the oil and again flood it out. 

As most crank seals are only rubber, their lifespan isn’t super long. They can wear down to nothing or go bad on you when you least expect it.

Finally, let’s discuss the cylinder piston rings. These split rings can expand as needed. The job of the piston rings is to wrap around the cylinder wall and seal the cylinder from the combustion chamber. The piston rings can also send oil towards the crankcase and generate heat between the cylinder wall and the piston.

As we’re sure you know we’re about to say, piston rings can break down, especially considering how hard they work. This is yet another impediment to your snowmobile starting up.  

Cylinder Lacks Compression

We said we would, so let’s talk more about the compression of your cylinder. 

Your engine cylinders need compression or they won’t work. It’s really as simple as that. When the cylinders have adequate compression, they can receive a fuel and air ratio, often in a tiny volume, that forces the molecules under pressure. 

How much pressure should the cylinders have? Each one needs 120 pounds per square inch of pressure or PSI at least. To do a pressure test, make sure you take the spark plugs out first. The engine should ideally be warm but not hot. Since your sled won’t turn on, a cold or cool engine will work in a pinch.

Pull the throttle open to allow optimal airflow into the cylinder. Then test. If your cylinder compression is 110 PSI, it’s too low. Once you hit 100 PSI, your sled probably won’t turn on.

If you have one or two troublesome cylinders, we’d recommend looking at all the cylinder parts we just covered in the last section. They’re what’s probably preventing your cylinder from getting pressure.   

Dead Spark Plugs

Moving away from cylinders now, another reason your snowmobile might not start is because of bad spark plugs. Without spark plugs, your snowmobile lacks the internal combustion that kickstarts the engine. Even one or two bad spark plugs could be enough to prevent your snowmobile from starting.

We recommend pulling out each spark plug one by one and cleaning them if you haven’t done that in a while (or ever). Test the plugs again by turning the engine on. Does your sled start? If so, then great. If not, then you probably need new spark plugs. You can get plugs for less than $10 each, so if they all went bad, don’t panic.

How do you install the new spark plugs? Open the hood of your snowmobile so you can reach the engine, then use a socket wrench to loosen each old plug until it comes out. Replace with your fresh spark plugs, close the hood, and your snowmobile should work. 

Fuel Line Blockages

The next few issues all have to do with your fuel line. You’ll want to inspect the fuel line closely, testing to see if anything is stuck in there. Debris and gunk can get backed up, preventing oil from traveling to your snowmobile’s engine. As you know, if the engine can’t get fuel, then your snowmobile won’t start. 

Once again, access the hood and remove the engine shroud. Using compressed air can push the blockages through the other end of the line so fuel can now flow freely. If that doesn’t work, then it’s not a bad idea to look into getting a new fuel line. This costs anywhere from $10 to $30, so it’s not terribly expensive. 

Dried-out Fuel Line 

When’s the last time you’ve used your snowmobile? If it’s been several months or even years, then the fuel line could have dried out between now and then. That can also happen if you don’t store your sled in optimal conditions over the summer. 

A carburetor cleaner can help in this case, as you need something to lubricate the fuel line. If the fuel line works but it’s brittle, then it’s not a bad idea to get a new one just to be on the safe side. 

Leftover Gas in the Tank

You also have to make it a point to remove all traces of last season’s gas before you retire your sled for the spring and summer. The gas that’s still there is stale, not to mention certain components might have settled and gotten gunky or sludgy. Clean out the gas that’s in the tank and then replace with completely new gas. 

How to Start Your Sled When Nothing Works

What if you tried everything that we suggested but to no avail? We’d recommend looking over your sled again, as one of the issues (or more) must be what’s causing your snowmobile not to start. If you’re still stumped, we’d suggest taking your snowmobile to a mechanic.

If you’re stranded and without any other options, a dash of starter fluid could get your sled running. However, many snowmobilers don’t mess with starter fluid because it can degrade seals and other internal components. Thus, you should use it at your own risk.

Do keep in mind that if you’ve used starter fluid on your sled before, then you’ll probably have to increase the quantity this time. That’s another issue with starter fluid, that it takes more and more of the stuff to get your sled to turn on each time you use it.  

Final Thoughts 

If your snowmobile won’t start, your issue lies in the fuel line, cylinders, or spark plugs. Go over these parts one by one, including all the many gaskets and seals a cylinder has. Relying on starter fluid to get your sled running can be a last-ditch measure, but one you should be reluctant to use. Best of luck getting your snowmobile to start! 

Geoff Southworth

I am a California native and I enjoy all the outdoors has to offer. My latest adventures have been taking the family camping, hiking and surfing.

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