Cold Weather Generator Starting: Choke, Fuel, and Oil

Start with the choke

Cold weather makes the first start of a portable generator harder because the engine is cold and fuel does not vaporize as easily. Use the choke to create a richer air-fuel mixture for the first few seconds of cranking. On most small generators, the correct cold-start routine is simple: close the choke, start the engine, then open the choke gradually as the engine warms and can run smoothly without it.

The choke is usually a lever or knob near the carburetor. If your generator uses a recoil starter, pull until the engine fires, then work the choke back toward the open position in stages. If the generator has electric start, you still need to manage the choke on most models unless the machine has an automatic choke. If the choke feels stiff or does not return smoothly, see how to adjust the choke.

• Turn the fuel valve on and check that the fuel shutoff is open.
• Close the choke for a cold start. On a warm engine, leave it open.
• Crank the engine, then gradually open the choke.
• If the engine floods, open the choke fully and let it clear before trying again.

Fuel for cold weather starts

Fuel is one of the main reasons a generator will not start when the temperature drops. Gasoline stored for months can lose the volatile compounds that help it ignite, leaving you with an engine that cranks but never catches. Before a cold-weather start, top up with fresh gasoline and, if the generator has been sitting, drain or stabilize the old fuel. A fuel stabilizer added at the right time makes fuel in the tank and carburetor more likely to stay usable between outages. See fuel stabilizer and storage life.

If your generator can burn more than one fuel, check the fuel selector and supply valve before you start. A dual-fuel generator lets you switch between gasoline and propane, and a tri-fuel model can also use natural gas. Knowing which fuel position to use in cold weather is part of reliable operation. Learn more about the tradeoffs in dual-fuel generator advantages.

Oil viscosity and winter starts

Oil viscosity has a big effect on winter starting. Cold oil is thicker, so the starter has to work harder to turn the engine. If the generator has been sitting in freezing temperatures, the oil might be sluggish enough to slow cranking and make the engine harder to start. Check the oil level before you begin, and use the viscosity grade the owner's manual recommends for the expected temperature. A multi-viscosity oil with a low winter rating flows better when cold than a single-grade oil in most cases. Details are in oil types and viscosity.

A low-oil shutdown is a safety feature that stops the engine when oil is too low. In cold weather, the oil level should be at the full mark, not close to the low mark, because the shutdown can prevent starting if the sensor thinks the level is unsafe. If the lamp is on after a cold start attempt, check the oil first. See low-oil shutdown.

Before you start: pre-start checklist

Run through this checklist before every cold start. It takes a minute and will save you from pulling a rope in the snow while the engine refuses to fire.

Cold weather carbon monoxide safety

The most important cold-weather rule has nothing to do with choke or oil: never start or run a portable generator inside a home, garage, basement, crawlspace, or shed. Carbon monoxide is colorless and odorless, and generator exhaust can contain dangerous levels. The U.S. Consumer Product Safety Commission warns that one generator can produce as much carbon monoxide as hundreds of cars and that it can kill in minutes. See generator carbon monoxide safety.

Keep the generator outside, at least 20 feet from windows, doors, and vents, with the exhaust pointing away from the home. Install battery-operated or battery-backup CO alarms on every level of the home and outside sleeping areas. If anyone experiences headache, dizziness, weakness, nausea, or confusion, move to fresh air immediately and call emergency services. Review the generator safety checklist outdoor use before the next storm.

How to make cold starts easier

Some features make cold starts less unpleasant. An electric-start generator can crank the engine at the touch of a button, which matters when pulling a recoil rope in cold air is difficult. It still needs a charged battery, so include battery maintenance in your winter routine; see electric-start battery. If you want quiet power for camping or RV trips in winter, an inverter generator may suit your needs.

Plan your winter storage before the storm arrives. Stabilized fuel, a clean air filter, and a battery maintainer can all make a cold start more predictable. If you exercise the generator periodically, you will know whether it starts before you depend on it. See generator exercise schedule.

What to pick for your use

Questions

Do I need to use the choke every time I start a generator in cold weather?

Use the choke when the engine is cold. A cold engine needs a richer mixture, and closing the choke supplies it. Once the engine has been running and is warm, leave the choke open. If you leave the choke closed too long after a start, the engine can flood and stall.

Can I start a generator in freezing rain or snow?

A portable generator must be outdoors, even in winter. Keep it in a dry, open area away from snowdrifts and provide protection from precipitation without enclosing the engine. The exhaust must stay clear.

Why does my generator start and then die in cold weather?

Often the choke was opened too early or left on too long. Stale fuel and the wrong oil grade can also cause stalling. Check the fuel, oil, and choke before troubleshooting further. See generator troubleshooting.

What oil should I use in a generator in winter?

Use the viscosity grade recommended by the manufacturer for the expected temperature. In cold weather, choose a multi-viscosity oil with a low winter rating so it flows more easily during cranking. Never run the engine with the oil below the full mark.

Is it okay to store a generator in a shed and start it there to keep it warm?

No. A shed is an enclosed space, and carbon monoxide can build up quickly. Only run a generator outside, at least 20 feet from the home, with exhaust facing away. A generator can be stored cold, but it must start and run outdoors.