Why is my generator smoking? White, blue and black smoke explained

Stop it right away if

• Smoke is coming from the generator's body, control panel or outlets, not the exhaust.
• You see sparks or flames, or smell burning plastic.
• Smoke is pouring out and the engine is knocking or losing power.
• You smell gas.

Champion's manual says not to use the generator if it "sparks, smokes or emits flames." OSHA says to power off and stop using any electrical equipment that "has strange odors or begins smoking."

To shut it down: turn off and unplug what's connected if you can do it safely, then switch the engine off. Keep clear until it cools. If there's a fire, get away from it and call 911.

What the smoke color tells you

Color	What it usually means	Common causes
White or blue-gray	The engine is burning oil	Too much oil, tipped or tilted, oily air filter, oil added to the cylinder for storage
Black	Too much fuel, not enough air	Dirty air filter, choke left on, flooded carburetor, bad fuel
A puff at startup that clears	Usually normal	Oil left in the cylinder from storage, or a just-oiled foam filter

Briggs & Stratton's troubleshooting guide puts it simply. White or blue smoke "means your engine is burning oil." Black smoke "could mean that the air filter is dirty, the fuel could have gone bad, the oil is overfilled, and/or the carburetor is flooded."

Smoke color is not a CO test. Carbon monoxide has no color or smell, so a generator can produce deadly levels with no visible smoke at all.

White or blue smoke: burning oil

Symptom: Gray-white or bluish smoke from the exhaust, often right after you start it. You may smell hot oil.

Why it happens: Oil has reached a place where it burns. Briggs & Stratton lists these causes:

• Running at more than a 15-degree angle. Champion's manual says to run the generator only on level surfaces.
• Tipping it on its side for storage, an oil change, or the drive home.
• Overfilling the oil past the dipstick mark.
• A blocked or crimped breather tube, behind the air filter.

Two more come from Honda's manual:

• An oil-soaked foam air filter. Honda says the engine "will smoke when started if too much oil is left in the air filters" after cleaning.
• Oil added to the cylinder for storage. Honda says the engine "may smoke briefly at startup" after this, and that it's normal.

How to check and fix it:

1. Shut it off and let it cool.
2. Move it to flat, level ground.
3. Check the oil on the dipstick, as your manual describes. If it's over full, drain some until it's at the right level.
4. Check the air filter. If it's dripping with oil, squeeze it out or replace it, following your manual.
5. Restart it. Briggs says smoke from tilting "should clear after a few minutes of running on a flat surface."

Smoking after an oil change? It's usually one of two things: too much oil went in, or oil spilled onto the engine or muffler and is burning off. Check the level, and wipe up any spills once the engine is cool.

If it won't clear: If the smoke keeps going with the generator level and the oil at the right mark, the cause is inside the engine. Briggs's mower guide says that if you see smoke and also have trouble keeping it running, "it's time for a serious look by a professional." Take it to a servicing dealer.

Black smoke: too much fuel

Symptom: Dark, sooty smoke from the exhaust, often with rough running, low power or a strong fuel smell.

Why it happens: The engine is getting more fuel than it can burn, or less air than it needs.

How to check and fix it, in the order Briggs & Stratton suggests:

1. Check the air filter. A clogged filter chokes off the air. Clean or replace it as your manual describes.
2. Check the choke. If it's still closed on a warm engine, open it. Champion warns not to over-choke, and to move the choke to RUN gradually once the engine starts. Too much choke fouls the spark plug.
3. Check the oil level. Briggs lists overfilled oil as a cause of black smoke too. Drain it to the correct level.
4. Replace the gas if it's old or might be contaminated.
5. Check the spark plug. If it's black and sooty, clean or replace it with the type in your manual.
6. Still smoking? The carburetor may be flooding or need cleaning. Briggs points to cleaning or rebuilding it. A flooding carburetor can also leak fuel into the oil, so check the oil for a gas smell before you run it again.

If it only runs with the choke on, the real problem is too little fuel at the normal setting. See generator only runs on choke.

At high altitude: Honda's manual says that at high altitude the standard air-fuel mixture "will be too rich," which can foul the plug. Honda recommends a carburetor change by a dealer if you always run above 5,000 feet.

Smoke when it's under load

Symptom: It runs clean at idle but smokes when you plug in a big load.

Why it happens: A heavy load makes the engine work its hardest, so a dirty air filter or a rich mix shows up most then. It can also mean the generator is overloaded.

How to fix it: Unplug some of the load and see if the smoke stops. Then fix the filter, oil or fuel as above. If the overload light comes on, see generator overload and tripping. If it also surges, see generator surging.

What not to do

• Don't keep running it while it smokes heavily. Find the cause first.
• Don't add more oil to "fix" smoke before you check the level. Overfilling is one of the causes.
• Don't run it on a slope or in the back of a truck to keep it out of the way. Champion says never to start or run a generator in the back of an SUV, camper or truck bed.
• Don't move it indoors or into a garage to look at it while it's running.

When to call a pro

Take it to a servicing dealer if:

• Blue or white smoke keeps going with the oil at the right level and the generator on level ground.
• It smokes and knocks, rattles or loses power.
• Oil smells of gas, or the oil level keeps rising.
• Smoke came from the alternator, control panel or outlets.

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