Rankedgenerators is audience-supported. When you buy through links on this site, we may earn an affiliate commission that we use for site maintenance. Learn more


Starting an Idle Generator in 2022: Everything You Need to Know

How to start a generator that has been sitting
Written by Jamie Masterson

Most generators are used in emergency situations, so there’s going to be long periods of time where the generator isn’t being used. Generators actually need to be run every so often to keep it functioning. When it sits unused, a number of problems can occur. Luckily, there are quite a few ways to get a cold generator running again. In this article, we’ll be showing you how to start a generator that’s been sitting for a while. Let’s get into it.

How to Start a Generator That Has Been Sitting

Jump start the battery

When a generator is running, it produces electromagnetism. This electromagnetism is used to keep the battery charged so it can provide the spark to the engine. However, the electromagnetism will eventually fade away and drain the battery of its charge. You need to run your generator to keep that energy reserve up.

If your generator isn’t starting, it’s a good idea to give the battery a jump to get things running. To do that, follow these steps.

  1. For this repair, you’ll need a pair of jumper cables and another power source. A car is the best option, but a portable power source works too.
  2. Attach the jumper cables to the battery terminals of your car or power source. Make sure it is off so you don’t get shocked.
  3. Attach the other side of the cables to the generator’s battery terminals.
  4. Turn your power source on.
  5. Try to turn on the generator. It should start right away.

If your generator is still not starting, then it’s time to move on to the next step to find out what the problem is.

Check the fuel level and color

Fuel doesn’t last forever. Most unleaded petrol fuels last about three weeks. After that time, a few things happen. First, components in the fuel begin to evaporate, which will change the compounds of the fuel. Next, the fuel begins to oxidize. When this happens, the fuel’s octane level lowers.

Low octane levels lead to carbon deposits that mess up the spark plug, preventing the spark from starting the generator properly. Low octane can also lead to overheating and piston damage.

  1. Open your fuel cap and take a look at your fuel. If it’s cloudy or murky, it needs to be changed.
  2. Replace the fuel with fresh fuel, then try restarting the generator. If it doesn’t start, it’s time to move to the spark plug.

Inspect and clean the spark plug

The spark plug in a generator provides the spark to start the engine. If your spark plug is dirty or damaged, your generator won’t start regardless of whatever repair you do. Before you start working on the spark plug, you’ll need a couple tools. Grab a socket wrench and a steel scrubber.

  1. Unplug all power cords and make sure the generator is completely off.
  2. Take the steel scrubber and scrub and debris or deposits around the spark plug. This prevents any loose dirt from getting in the plug.
  3. Remove the spark plug cap.
  4. Take the wrench and loosen the spark plug.
  5. From here, take the steel wool and clean out any debris or build-up.
  6. Check the spark plug for any damage. If there’s damage, you’ll need to replace the spark plug completely.
  7. Once it’s clean, stick the spark plug back into the socket and place the cover.

Clean or replace the air filter

Air filters will always get dirty, but if its sitting unused, it will collect more dust than usual. When this happens, there isn’t enough air flow to get the correct combustion for the engine to start. To check and clean the air filter, you’ll need a flat head screwdriver to open the cap.

  1. Remove the panel from the air filter box using the flat head screwdriver.
  2. Take out the air filter.
  3. If the air filter is extremely discolored and dirty, it’s time to replace it.
  4. Clean the air filter as much as you can. Be gentle so you don’t damage it.
  5. Re-place the air filter back in the box and tighten the screws.

Clean the carburetor

The carburetor of a generator mixes fuel and air to cause the combustion reaction. Fuel is injected directly into the carburetor, so there’s always a bit of fuel in it. When you leave the generator for a long time, that fuel will start to deteriorate. Even if you replace the fuel, the leftover stuff in the carburetor will still affect the generator.

To clean the carburetor, you’ll need a socket wrench to loosen the carburetor.

  1. Detach the fuel lines from the carburetor.
  2. Loosen the bolts on the carburetor with the socket wrench. Be extremely careful when doing this since any damage could compromise the carburetor.
  3. Drain any excess fuel in the carburetor.
  4. Put the fuel lines back onto the carburetor.
  5. Re-attach the carburetor. Use the wrench to tighten the bolts.

Dry the fuel lines

Moisture will start to build up in the fuel lines if they are left for a long time. The moisture will make your fuel dirty, inefficient, and possibly dangerous. Tainted fuel can lead to overheating, which can cause some serious damage to your generator and to you. Before starting the generator, check the fuel lines.

  1. The fuel lines are attached to the carburetor. Gently remove the fuel line clamps, then remove the lines.
  2. You can either let them air dry or take a small cloth and dry them manually.
  3. Once they are dry, put the fuel lines back on. Make sure you are using new fuel as well.


Q. How long can a generator sit?

Most generators shouldn’t sit for more than few months, but some makes can be sitting for a long time. Check your generator’s manual for more specific information.

Q. Can I use another kind of fuel?

Only use fuel that is recommended by the manufacturer. Adding incompatible fuels can cause havoc on the engine. These machines are built for specific purposes and aren’t really meant have any changes.

About the author

Jamie Masterson

With decade-long experience as a generator technician, Jamie has worked with USA’s top generator manufacturers and suppliers as an independent contractor.

The long years of service to the industry has taught Jamie the ins and outs of troubleshooting, repairing, and maintaining all kinds of generators in home, industrial and outdoor settings.

Jamie thinks this platform is a great opportunity to share his tips and tricks with you so you can make the most of such power equipment for better living.

Leave a Comment