When a snow blower will not start it feels like a mystery, and it almost never is. The machine needs fuel, air, spark and compression, and on a snow blower that has sat since March, one of those has quietly gone wrong. This guide diagnoses it in order of likelihood so you fix the actual fault rather than replacing parts in hope.
Check these four things first
Before assuming anything is broken, rule out the four faults that are not faults at all. Between them they explain a surprising share of the calls we take. Most cases where a snow blower will not start end right here.
| Check | What people miss | Fix |
|---|---|---|
| Fuel valve | Left closed after summer storage | Turn it fully open |
| Safety key | Half seated feels identical to a dead engine | Push it fully home |
| Choke | Open on a cold engine, or closed on a warm one | Closed for cold, off for warm |
| Throttle | Left on slow | Set to fast before pulling |
Work through those before touching a spanner. If the machine still will not fire, the sequence below moves from most to least likely, which is also cheapest to most expensive. A snow blower will not start for very few reasons, and this is the first.
Fuel, the cause of most no starts
If you remember one thing from this page: a snow blower that will not start in December was almost certainly put away badly in April. Work down the list whenever a snow blower will not start. If a snow blower will not start twice running, stop pulling and diagnose.
Petrol is not stable. Left in a tank through a warm summer it separates, the lighter fractions evaporate, and what remains leaves a varnish in the carburettor jets. Those jets are very small. It takes very little deposit to block them. The engine then cranks normally, may cough once, and never runs.
The fix, in order:
- Drain the old fuel completely. Do not top it up with fresh and hope; you are diluting a problem, not removing it.
- Refill with fresh petrol and add fuel stabiliser now, so this does not repeat next year.
- Try starting from the cold sequence. If it fires and runs, you were lucky and caught it early.
- If it fires and dies, or will not fire at all, the carburettor needs cleaning. On most machines that is four bolts and an afternoon.
- If cleaning does not restore it, fit a carburettor kit or a replacement carburettor assembly.
Modern fuel with ethanol content makes this worse, because ethanol attracts water and the two separate in the tank. That is why a machine can have clean looking fuel and still refuse to run. When a snow blower will not start under load, suspect supply rather than spark.
Carburettor assemblies, kits, fuel lines, filters and shut off valves are all listed by stock number on the parts catalogue. It is rarely serious when a snow blower will not start.
No spark at all
Test before you buy anything. Remove the spark plug, reconnect the lead, hold the threaded body against bare metal on the engine, and pull the recoil. You should see a blue spark. Wear gloves and keep your fingers off the terminal.
| What you find | Cause | Fix |
|---|---|---|
| No spark, plug looks black and wet | Fouled plug | New plug, a few dollars |
| No spark, plug looks clean | Safety key or kill switch lead | Seat the key, check the lead is not grounded |
| No spark with a new plug and key seated | Ignition coil | Coil replacement |
| Weak orange spark | Failing plug or coil | Plug first, it is cheaper |
| Good blue spark | Ignition is fine | Move to the fuel section |
Fit a new plug first regardless. It is the cheapest part on the machine, it is a consumable, and a plug that has done two seasons of short cold runs is usually due anyway.
Starts then dies
This is good news disguised as a problem. The engine fired, so ignition and compression are working. What it cannot do is keep feeding itself.
| Symptom | Cause | Fix |
|---|---|---|
| Runs on choke, dies when choke opens | Blocked idle circuit | Carburettor clean or kit |
| Runs a few seconds, dies, repeatable | Blocked fuel line or filter | Check valve fully open, then filter |
| Fires once, never again | Stale fuel or water in the tank | Drain, refill with fresh fuel and stabiliser |
| Dies only when you engage the auger | Fuel starvation under load | Filter and line before suspecting the engine |
| Dies after several minutes, restarts when cool | Blocked tank vent | Loosen the fuel cap and retry |
The tank vent one is worth knowing because it looks alarming and costs nothing. If the cap vent blocks, a vacuum forms in the tank and starves the engine. Loosen the cap; if the machine then runs, you have found it.
Surging and running rough
Surging is the engine hunting up and down without you touching the throttle. It means the mixture is alternately too lean and correcting, and the cause is nearly always a partly blocked main jet.
Running the machine will not clear it. Neither will fuel additive at this stage, though additive would have prevented it. The fix is a carburettor clean, and if the machine has been sitting for more than a season, a carburettor kit with new gaskets and a diaphragm is the more reliable route.
Rough running under load with no surge at idle is a different fault, usually a failing plug or a partly blocked filter restricting flow when demand rises. Work through the repair guide for the full sequence.
Electric start problems
Electric start on a petrol snow blower is typically a 120 volt starter that plugs into a mains lead, not a battery starter.
- Starter turns the engine but it never fires. The starter is doing its job. The fault is fuel or spark, so go back to those sections.
- Starter hums or clicks without turning. Check the extension lead rating before condemning the starter. An underspecified or cold stiffened lead is a very common false alarm. Use a 12 gauge cold weather rated outdoor lead.
- Nothing at all. Check the outlet with something else, then the lead, then the machine.
- Worked, now does not. Continuous cranking overheats these starters. Use five second bursts with ten seconds between.
Cordless and corded machines
Battery and corded machines fail differently, and none of the fuel advice above applies. They are also the majority of what we stock, so this section matters.
| Symptom | Cordless cause | Corded cause |
|---|---|---|
| Nothing happens at all | Pack not fully seated, or safety key out | Lead not connected, or breaker tripped |
| Runs briefly then stops | Pack too cold, or nearly flat | Thermal cut out after a heavy bite |
| Much shorter runtime than year one | Cells ageing, usually around year six | Not applicable |
| Cuts out under load, still shows charge | Cold pack, or a wet snow current spike | Undersized extension lead |
| Trips the breaker | Not applicable | Shared circuit or undersized lead |
The cold pack case is the one people misread as a dead machine. A pack stored in an unheated garage at minus twenty may refuse to deliver current until it warms. Bring it indoors for twenty minutes and try again before ordering anything.
For corded machines, the lead is the fault far more often than the machine. A lightweight indoor extension stiffens and drops voltage in the cold, which reads as a machine that cuts out.
What each repair costs
Real prices from our own catalogue, so you can judge repair against replacement rather than guessing.
| Repair | Our listed price | Difficulty |
|---|---|---|
| Spark plug | A few dollars | Five minutes, no tools beyond a plug spanner |
| Carburettor gasket | Low, sold with kits | Afternoon job, four bolts |
| Carburettor assembly | $55.75 | Afternoon job |
| Auger belt | $20.91 | Belt cover off, straightforward |
| Friction wheel assembly | $55.06 | Moderate, drive side |
| Gear box assembly | $83.63 | The expensive one, usually avoidable |
Set against a machine costing several hundred to several thousand dollars, almost every no start is worth repairing. Replacement only makes sense when the engine or gearbox has failed, and the gearbox usually only fails because someone fitted a hardware bolt where a shear pin belonged.
Compression, and when to stop trying
Fuel and spark cover almost everything. Compression is the rare fourth possibility, and it is worth knowing how to recognise because it changes the economics.
Pull the recoil slowly. You should feel a clear point of resistance as the piston comes up on the compression stroke. If the cord pulls through smoothly with almost no resistance anywhere, the engine has lost compression, and that is a valve, ring or head gasket problem rather than a carburettor one.
At that point the arithmetic changes. A carburettor at $55.75 on a $1,600 machine is obvious. A top end rebuild on the same machine may not be, particularly if it is ten years old and the gearbox has also had a hard life. This is the one case where replacement is genuinely the sensible answer, and it is also the rarest.
Loss of compression is usually the end of a long story rather than a sudden event: running low on oil, running hot, or years of short cold cycles. It is why the oil check before every start matters more than any other habit on this page.
The diagnostic order, in one list
If you want a single sequence to work through without reading the whole page, this is it.
- Fuel valve open, safety key seated, throttle fast, choke correct for temperature.
- Is the fuel fresh? If it has been in the tank since spring, drain and refill before anything else.
- Pull the plug. Fouled, wet or black? Fit a new one.
- Test for spark against bare metal. No spark with a new plug means key, kill lead, then coil.
- Good spark and fresh fuel but it fires and dies? Carburettor.
- Surging? Carburettor main jet.
- Dies under load only? Fuel filter and line.
- No compression on a slow pull? Stop, and price a replacement against a rebuild.
Nine of ten machines are fixed by steps two and three.
When a snow blower will not start, check fuel first
To summarise: snow blower will not start comes down to matching the machine to the surface, the snowfall and the space you have to store it. Everything above is the detail behind that. If any of it is unclear for your property, ask us rather than guessing. If your snow blower will not start after this, move down the list.
How to never have this problem again
Every fault on this page except a failed coil is preventable, and the prevention costs less than one workshop visit. Ask us if a snow blower will not start after all of this.
- Stabiliser in April, not October. Add it to a full tank at the end of the season and run the engine long enough to carry treated fuel through the carburettor. This single habit prevents most of what is described above.
- Or drain it dry. If you would rather not store fuel at all, run the tank empty and then run the engine until it stops.
- Change the oil at the end of the season. Used oil holds acids that sit in the engine all summer.
- New plug every two or three seasons. It costs a few dollars and removes an entire failure category.
- Run it for ten minutes on the first dry day of autumn. Faults then surface on your schedule, not during the first storm when every workshop in the country is three weeks deep.
- Store it off bare concrete. Concrete wicks moisture into the underside of the machine.
The full seasonal routine is set out in the maintenance checklist. For starting technique rather than faults, see how to start a snow blower.
Canadian standards for outdoor power equipment are published by the CSA Group.
Common questions
Why will my snow blower not start after summer?
Fuel, nine times out of ten. Petrol left untreated over a Canadian summer separates and leaves a varnish in the carburettor jets. The engine cranks, sometimes coughs, and never runs properly. Drain the old fuel, refill with fresh petrol and stabiliser, and if it still will not run, the carburettor needs cleaning rather than more pulling. That is the most common reason a snow blower will not start.
My snow blower will not start and there is no spark. What now?
Check the safety key is fully seated and the kill switch lead is not loose or grounded against the frame, then fit a new spark plug. Plugs are the cheapest part on the machine and a fouled one is extremely common after a season of short runs. If a new plug still gives no spark, the ignition coil is the next suspect. Stale fuel is why a snow blower will not start more than anything else.
Snow blower starts then dies straight away. What causes that?
The ignition is fine, so it is fuel supply. Most often a blocked idle circuit in the carburettor, sometimes a partly closed fuel valve or a blocked filter. It will run on choke and die when the choke opens, which is the classic signature.
Why does my snow blower surge up and down?
A partly blocked main jet. The engine alternately starves and recovers, which produces the hunting note. Running it will not clear the blockage. Clean the carburettor or fit a carburettor kit.
Is it worth repairing or should I replace the machine?
Repair, almost always. The common failures here are a carburettor, a plug, a belt or a friction wheel, and together those cost a small fraction of a new machine. Replacement only makes sense when the gearbox or the engine itself has failed, which is rare and usually preventable.
Parts by manufacturer stock number are on the parts catalogue, the full fault sequence is in the repair guide, and if you would rather describe the symptom to a person, use the contact page.