Generator won't start after sitting in the shed all winter — any ideas?

Same thing happened to me last spring when I finally got round to commissioning the boat after months sitting in the marina yard. Honda EU22i, wouldn't fire for love nor money.

Nine times out of ten with a generator that's been sitting, it's the carburettor. Stale petrol goes almost varnish-like and gums up the jets something awful. Here's what sorted mine:

1. Drain the carb completely — there's usually a small drain screw at the bottom
2. Fresh fuel — sounds obvious but old ethanol-blended petrol degrades fast, especially over winter
3. Carb cleaner spray through the jets if draining alone doesn't crack it
4. Check the spark plug — pull it out, it should look greyish-tan, not black or fouled
5. Fresh oil — some generators won't start with low or degraded oil due to the low-oil cutoff sensor

If you're storing a generator seasonally, either run it completely dry of fuel before putting it away, or use a fuel stabiliser like Sta-Bil — I've sworn by it ever since that marina incident.

Also worth checking the air filter hasn't become home to a mouse nest. Found exactly that in my cabin generator one February. Not pleasant.

What make and model are you dealing with? That might narrow it down — some generators have their own quirks. The Kipor inverter units I used before switching to a Victron/Fogstar setup had a notorious choke sensitivity issue in cold weather.

Others on here will likely have more generator-specific wisdom — what's everyone else's go-to first fix?

Stale fuel in the carb is the silent killer — drain it completely and she'll probably fire on the second pull like nothing ever happened.

Drain the float bowl, squirt a tiny bit of fresh fuel directly into the carb throat, and if she still sulks — check the spark plug hasn't gone the colour of a well-used ashtray.

@WayneKnight and @ExFarmer have covered the fuel side well. One thing I'd add — have you checked the spark plug? After a long winter sit, I pulled mine out on my generator and it was absolutely furred up with carbon deposits. A quick clean with a wire brush or a £2 replacement plug made all the difference.

Also worth checking the oil level if there's a low-oil cutoff sensor — mine was borderline and the safety circuit was preventing it from firing at all. Took me ages to work that one out.

What model is yours? Some older generators have a fuel tap that's easy to accidentally leave in the off position over winter too. Sounds obvious but I've done it myself.

@Bomber's spark plug point is solid — worth pulling it out and checking the electrode gap while you're at it, they drift over time.

One thing nobody's mentioned yet: the air filter. Sitting in a damp shed all winter, they can get moisture-logged or even grow a bit of mould. A clogged filter will starve the engine and make it crank endlessly without catching.

Also check your oil level — some Hondas have a low-oil cutoff that prevents starting, and oil can settle/drop slightly over a long storage period.

My EU22i lives in the outhouse next to the tiny house and I now run it for 20 minutes every 6-8 weeks through winter just to keep everything happy. Saves a lot of faff come spring.