Generator won't start after sitting in the shed all winter — where do I even begin?

Been through this exact nightmare with a Honda EU22i that sat untouched from October to March.

First things first — the carburettor is almost certainly your culprit. Old petrol goes stale and leaves a varnish-like residue in the jets. Pull the bowl off, spray everything with carb cleaner, and check the main jet is clear. Tiny hole, massive difference.

My checklist in order:

• Fresh fuel — drain whatever's in there, it's probably grim
• Spark plug — pull it, check the electrode, replace if in any doubt (they're a quid)
• Air filter — give it a clean or swap it
• Oil level — some generators won't even attempt to start with low oil (low-oil cutoff switch)
• Choke position — sounds obvious but worth stating

If the carb is really gunked up, a full soak in carb cleaner overnight can work wonders. Failing that, a replacement carb for most Chinese generators is about £8–15 on eBay.

Going forward I always add Briggs & Stratton fuel stabiliser before winter storage and run it for a few minutes to get it through the system. Saves so much grief.

What make/model are you working with? Some generators are more prone to this than others — certain carb designs seem to clog just looking at them. Also, how long had it been sitting before you put it away — was the fuel fresh or already a few months old?

Others on here will have more specific tips depending on your setup. This stuff is usually fixable without spending much.

Gazza55 | 847 posts

@BoatMel solid advice on the carb, totally agree. One thing worth adding before you even get that far — check your spark plug first. Dead easy, takes two minutes, and a fouled or corroded plug is surprisingly often the actual villain after a long winter sit. Pull it out, have a look at the electrode, and if it's black and sooty or showing any corrosion just fit a new one. They're a quid or two and you might save yourself stripping the carb unnecessarily.

Also worth draining any old fuel from the tank completely before adding fresh — don't just top it up over the stale stuff. I learned that the hard way with my old Kipor years back. Fresh fuel, new plug, then tackle the carb if it's still being stubborn. Good luck with it!

@BoatMel @Gazza55 — this is almost word-for-word my first spring with the generator I keep for emergency backup at our place here.

What nobody told me: even after a full carb clean, if the spark plug has sat damp all winter it'll fire weakly or not at all. Pulled mine out last March expecting a gunked carb, carb was actually fine — but the plug looked like it had been through the Somme.

A fresh NGK plug is about £4 from any motor factors. Worth swapping it blind as part of your winter-wake-up routine rather than waiting to diagnose.

Also — fresh fuel, not the stuff left in your jerry can from last autumn. E10 goes off surprisingly fast, especially in cold storage.

Right so here's a thing nobody mentions — the spark plug.

Last March I'm stood in a muddy field next to my van, Fogstar battery bank reading critically low after a week of solid cloud, and my little generator just wheeze-coughs and dies repeatedly. I'd already done the carb dance @BoatMel describes. Spent two hours feeling very clever about it.

Pulled the plug on a whim. Absolutely coated in this weird caramel-coloured gunk from the old fuel residue burning off badly.

£3 replacement from the local motor factors, gaped it properly, and the thing fired on literally the second pull.

Worth checking before you order a full carb kit honestly. Sometimes the fix is embarrassingly simple and cheap, which is basically the opposite of how my van conversion projects usually go. 🙃

Really useful thread this — got me thinking about my own setup on the van and the little narrowboat I'm slowly converting.

@DriftWizard the spark plug point is genuinely underrated. Can I ask — do you carry a spare as standard kit now?

One thing I haven't seen mentioned yet: the oil low-level cutoff switch. After winter storage the oil can settle or levels drop slightly, and some generators simply won't attempt to fire if that sensor triggers. Worth checking oil level before you even pull the cord — could save you tearing half the carb apart unnecessarily.

Also, is anyone running a fuel stabiliser like Sta-Bil through theirs before laying up? Wondering if that genuinely makes a difference to spring startups or if it's marketing fluff?

Good points all round but nobody's mentioned the fuel tap/petcock yet. On a lot of the smaller Honda and Kipor units there's a rubber diaphragm in there that perishes over time — it sticks closed and the engine either won't start or runs for 30 seconds then dies. Classic winter storage symptom and people spend ages cleaning carbs when that's the actual fault.

Also worth checking the oil level sensor — some generators won't even attempt to fire if the oil's slightly low after sitting, and they give zero indication why. Top it up before you do anything else, saves a lot of head-scratching.

For my static caravan setup I now run the generator monthly through winter on a 30-minute load test. Bit of discipline but it means spring isn't a drama.