It ran fine when you put it away, and now after a season in the shed it won't fire. Nine times out of ten this isn't a dead engine — it's the fuel that went stale while it sat. Here's how to bring it back, cheapest fix first.
A machine that ran fine last season and won't start after months in storage almost never has a "broken" engine — the storage itself is the problem, and specifically the fuel. Gasoline begins to oxidize within about a month, and over an off-season the volatile parts evaporate and leave behind a gummy varnish. That varnish settles into the carburetor's tiny jets and passages and chokes off the fuel the engine needs to fire. So the fix usually isn't a new part — it's getting clean fuel through a clean fuel system again.
That's why this guide works fuel-first. Only once the fuel side is ruled out do you move to spark and air, and finally to cleaning the carburetor itself. If your machine does start but then misbehaves — surging, stalling, or losing pressure — that's a different set of problems that trace to the unloader valve, not to storage. This page is specifically for the no-start.
It worked when you stored it and now won't start after sitting for weeks or months — the classic post-storage or first-of-the-season no-start.
It starts but then surges at idle, stalls when you release the trigger, or makes no pressure — those are running problems, not starting ones.
Work top to bottom. Fuel comes first because stale gas causes the large majority of post-storage no-starts and costs nothing to rule out; the carburetor cleaning comes later because there's no point tearing it down if fresh fuel and a new plug bring it back.
The number one cause after storage, and free to fix. Gas left untreated for a season loses the volatility it needs to ignite and starts turning to varnish. A tank of old fuel will crank and crank without firing.
Easy to skip after months away from the machine. A cold engine needs the choke closed to start; the fuel valve has to be open; and the on/off switch and throttle have to be in the run position. Any one of these left wrong reads as a dead engine.
A plug that was marginal at the end of last season often won't fire after sitting, and a plug fouled by old fuel or carbon won't spark cleanly. It's a cheap part and a fast check that rules out the ignition side.
Dust and debris that settled in over storage can block the air filter, and an engine that can't breathe won't start or will only cough. It's another quick, cheap thing to eliminate before opening the carburetor.
The deeper version of the stale-fuel problem, and the most common reason fresh fuel alone doesn't fix it. Varnish from old gas clogs the carburetor's tiny jets and passages, so even good fuel can't get through in the right amount to fire.
Last, once fuel and carb are addressed: the fuel filter can clog with sediment from old gas, and rubber fuel lines can dry, crack, or harden over a season so they leak air or restrict flow. Either one starves the carburetor even after you've cleaned it.
How it fails to start narrows down where to look first. Use this to jump to the likely cause, then confirm with the step above.
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| What you notice | Look first at |
|---|---|
| Cranks but never fires, old gas in tank | Stale fuel — drain and refill |
| Won't even attempt to catch | Choke / fuel valve / switch |
| Coughs or fires once then quits | Fouled spark plug |
| Sat in a dusty shed all season | Clogged air filter |
| Fresh fuel and new plug, still won't fire | Gummed carburetor |
| Runs briefly on primer then dies | Fuel filter or cracked line |
A post-storage no-start is almost always fixed with fresh fuel and a few cheap parts — a plug, a filter, a carb kit — not a new engine. Match the exact part to your machine's engine model before ordering; the engine's parts diagram is the quickest route to the right fit.
Added to fresh gas before storage, it stops the varnish that causes most seasonal no-starts. The cheapest prevention there is.
Find stabilizer →A fresh plug rules out the ignition side and is cheap insurance at the start of each season.
Find the plug →A clean filter lets the engine breathe. Replace a dirty or damaged element rather than fighting a clogged one.
Find the filter →Fresh gaskets, diaphragms, and seals to clean up a varnished carburetor — the fix when fresh fuel isn't enough.
Find the kit →Replacement filter and fuel line for gunked or cracked fuel delivery after a season of old gas.
Find the parts →Flush-and-store lubricant that protects the pump seals over the off-season — part of storing it right next time.
Find pump saver →The overwhelming cause is fuel that went stale in storage. Gas oxidizes within about 30 days and, over months, turns to a gummy varnish that clogs the carburetor. The causes, cheapest first, are stale fuel, a setup or choke oversight, a fouled spark plug, a clogged air filter, a gummed carburetor, and a clogged fuel filter or cracked line. Drain the old fuel and add fresh before assuming anything is broken.
A clogged carburetor from stale fuel, by a wide margin. When gas sits untreated, the light compounds evaporate and leave varnish that blocks the tiny jets inside the carburetor. Fresh fuel sometimes fixes it if you catch it early; if not, the carburetor needs cleaning or a rebuild kit. This one issue causes most seasonal no-starts, which is why fuel is always the first check.
Yes — it's the number one cause after storage. Gas older than about 30 days without stabilizer loses volatility, and by 60 to 90 days it turns gummy enough to clog the fuel system. Adding stabilizer after the fact won't reverse degradation that's already happened. Drain the stale fuel, refill with fresh, and try to start before moving on.
With the engine cool and the spark plug wire disconnected, remove the bowl and spray carb cleaner through the jets and passages — the tiny holes in the bore especially. Soaking parts overnight helps stubborn varnish. Blow the passages clear with low-pressure air, wear eye protection, and reassemble with fresh gaskets from a rebuild kit. Under warranty, have a technician do it instead.
Prevention is mostly fuel. Before storing, either run the tank dry or add stabilizer to fresh gas and run the engine a few minutes so treated fuel reaches the carburetor. Flush the pump with a pump-saver product, store it dry and covered, and fit a fresh plug at the start of the season. Done that way, most machines start on the first or second pull.