Generator won't start? Check these causes in order

Try these first

1. Unplug everything from the generator. Makers say not to start it with a load connected.
2. Check the engine switch is ON and the fuel valve is open. On some models, the fuel cap has a vent lever that must be ON too.
3. Check there's gas in the tank.
4. Check the oil level with the generator on flat, level ground.
5. Set the choke correctly for a cold engine.
6. If it still won't start, work through the sections below.

A switch, valve or vent is off

Symptom: The engine turns over but never catches, or doesn't even try.

Why it happens: A generator has several on/off points, and each one can stop it. Generac's first checks are fresh gas and oil, the fuel shut-off valve, and the on/off switch. Honda's troubleshooting table starts with the fuel cap vent lever and the engine switch.

How to check and fix it:

1. Turn the engine switch to ON.
2. Turn the fuel valve to ON.
3. If your fuel cap has a vent lever, set it to ON.
4. On push-button models, Generac notes the power switch must be on before you press start.
5. On electric-start models, check the battery switch is on. A dead starter battery won't crank the engine. Charge it, or use the pull cord.

Low oil has triggered the shutdown

Symptom: It won't start, or it starts and dies within seconds. Some models flash an oil light when you pull the cord.

Why it happens: Most generators have a low-oil shutdown. It stops the engine before low oil can damage it. Honda says that if the engine stops or the oil light comes on when you pull the starter, you should check the oil before troubleshooting anything else. Champion lists low oil and unlevel ground as causes of both "will not start" and "starts but runs roughly."

How to check and fix it:

1. Move the generator to flat, level ground.
2. Check the oil with the dipstick. Follow your manual. Some dipsticks are read without screwing them in.
3. Top up with the oil type your manual lists.
4. Try to start it again.

Never disconnect or bypass the low-oil sensor to get it running. See low oil light but oil is full if the oil looks fine.

Stale or bad gasoline

Symptom: It sat for a few months and now won't start, or it sputters.

Why it happens: Gas goes stale. Honda's manual says fuel can deteriorate in as little as 30 days. Old gas causes hard starting and leaves gum that clogs the fuel system. Honda lists "bad fuel; generator stored without treating or draining gasoline" as a cause of an engine that won't start.

How to check and fix it: Drain the old gas and refill with fresh. Our won't start after sitting guide covers this step by step, including when the carburetor needs cleaning.

A fouled, wet or worn spark plug

Symptom: Plenty of fresh fuel, the oil is full, but no start.

Why it happens: Generac says the most common cause is a damaged or faulty spark plug that must be replaced. Honda lists a plug that is faulty, fouled or wrongly gapped, and a plug wet with fuel from a flooded engine.

How to check and fix it:

Before you start: engine off and cool, spark plug wire disconnected, outdoors, and no flames or sparks nearby. Champion's service notes say the same: stop the engine, pull the plug wire, and let it cool fully.

1. Pull the spark plug cap off.
2. Remove the plug with a spark plug wrench.
3. Look at the tip. If it's wet with fuel, the engine is flooded. Honda says to dry the plug and put it back.
4. If it's black and crusty, or the electrode is worn, replace it with the plug type in your manual.
5. Set the gap to the figure in your manual using a feeler gauge.
6. Thread the plug in by hand first, then snug it with the wrench. Refit the cap firmly.

Choke set wrong, or a flooded engine

Symptom: It coughs but won't keep going, or smells strongly of gas.

Why it happens: A cold engine needs the choke on to start. A warm engine usually needs less or none. Too much choke floods it. Champion lists "choke in the wrong position" as a cause. Its manual also says not to over-choke, and to move the lever to RUN gradually once the engine fires.

How to check and fix it:

1. For a cold start, set the choke to full, or to the position your manual gives.
2. Once it fires, ease the choke toward RUN over a few seconds.
3. If it's flooded, take the plug out and check it. Honda's fix for a plug wet with fuel is to dry it and reinstall it, as above. Then try again with less choke.

Something is plugged in

Symptom: It struggles to start, or stalls the moment it catches.

Why it happens: Champion lists "unit loaded during start up" as a cause, and says to never start or stop the generator with devices plugged in. Generac adds that generators need to stabilize and warm up before you add appliances.

How to fix it: Unplug everything. Start it, let it run a few minutes, then plug things in one at a time.

When to stop and call a pro

Have it serviced if:

• It still won't start after fresh fuel, the right oil level, a new plug and the right choke.
• You smell gas when it's parked, or see fuel leaking.
• The pull cord is locked solid and won't move.
• Honda lists a restricted fuel filter, a carburetor fault, an ignition fault or stuck valves as dealer jobs.

Generac and Honda both send you to an authorized service dealer at this point. If the unit is under warranty, call the maker before you open anything.

Run it outdoors only, 20+ feet from the house: generator carbon monoxide safety.