How To Start A Generator That Has Been Sitting? (Complete Guide)

Buying a generator is a great way to have a backup plan in case of an emergency. Since generators are rarely used, they are usually left idle for a while before being used. Sometimes this causes them to not start properly. And then there’s the question, how to start a generator that has been sitting?

First things first, and before you do anything with your generator, you need to get the owner’s manual out and at least keep it around in case you run into any problems.

How do you start a generator that won’t start?

If the generator has not been used for a long time, it may not start for various reasons. However, this is not too worrying and can be fixed with the following steps:

Basic check-up. The first thing you need to do before disassembling the engine is to have a basic inspection. Make sure your generator has enough fuel. Also, check that the fuel valve is open and that the choke switch is on.

If the oil level is low, add it. In modern generators, an oil sensor is designed for this purpose. Here, keep in mind that even with enough oil, the low oil level sensor may trip if the generator is placed on an uneven surface.

Add fresh fuel. Another common reason why a generator that has been idle for a while will not start is stale gasoline. This is a very common problem that is easily fixed with fresh gasoline.

It is very important to change the oil and gas regularly if your generator has not been used for a long time.

To avoid this in the future, run the portable generator dry after use. You can also use a fuel stabilizer.

Check the fuel valve. Fuel flow from the gas tank to the carburetor is controlled by a fuel valve. The fuel valve gas tank must be open and not clogged.

To see if it is clogged, disconnect the outlet hose from the fuel valve, and if you can find that the gasoline is not flowing freely, the valve should either be cleaned or replaced with a new one. If there is a filter installed between the fuel cock and the carburetor, pull it out and check if it is clogged.

Check the positioning of the choke. The function of the choke is to control the flow of air through the carburetor when the generator is started. If the generator is to be started after a long time, the throttle must be closed, which is the start position.

On the other hand, if the generator has recently shut down but still won’t start, adjust the damper halfway or open it all the way to restart.

Check the spark plug. The fifth item on your checklist is the engine’s spark plug. Simply unplug it to check its condition. Take a carb cleaner to clean it if the spark plug is dirty. After removing the spark plug, you should also spray carb cleaner into the cylinder. There is a chance that the generator will not start even if you followed the rest of the steps correctly.

There is a chance that the spark plug is worn out, even if it still looks normal. Therefore, you should try to replace the ignition coil. If the sparks are strong with a blue color, then the ignition coil is good. If sparks now appear between the spark plug cap and the engine crankcase, the spark plug must be replaced. If there is no spark, the ignition coil may need to be replaced.

Check the air filter. After checking the spark plug and fuel and doing a basic check, move on to the air filter. In order for the generator to function properly, it must have adequate airflow. A working airflow allows the machine to do just that.

Sometimes the air filter can become clogged and prevent the generator from starting. Pull out the air filter and check whether it is clogged or not.

Even if it looks good, clean it to make sure it looks good. If you find it is clogged or looks worn, replace it with a new air filter.

The fuel line and fuel filter. If after all other checks, the generator still does not start, the fuel line should be checked. Any jammed, clogged, cracked, or even leaking line can cause the generator to stop working after an extended period of inactivity. Damage along the gas line can sometimes be relatively easy to repair.

The fuel lines can easily become clogged, especially when using adulterated fuel. In most cases, the safest way to make sure the engine is locked is to remove the fuel line by disconnecting it from the carburetor.

After disassembling the device, pay special attention to whether the fuel passes through the filter or not. If you notice that there is no gas outlet, it is most likely blocked. In this case, the fuel line must be replaced.

Clean the carburetor. The last thing you can do to get a sitting generator running is to clean the carburetor. You need to get some kind of car cleaner to do the job. All you have to do is spray it around the carburetor and injectors.

Sometimes it is necessary to remove the carburetor to clean it. It is very important that the part is not scratched or damaged when removing it. It is good practice to clean the carburetor to ensure that there is no old fuel in it.

Check the battery and other electronic connections

In the case of an electric start generator, it can be discharged for a long period of time.

To fix this, try starting the generator with a manual starter or third-party battery charger.

If the battery sounds good, check to see if the fuse is blown. Sometimes, due to excessive current flow, the metal strip in the fuse melts, causing it to burn out. As a result, the entire electronic circuit fails.

If the electronic connections are not cleaned for a long time, they will wear out due to corrosion. So, if so, clean the terminals with a wire brush.


The above issues are common when trying to start the generator after a long period of time. Hopefully, your generator will start after following the steps above. However, if it doesn’t, then there could be serious technical issues with the engine, and you may want to call a mechanic to get the job done.

If you are interested in how a solar generator works you can read this article: Solar Generator: How Does Solar Generator Work?

Frequently Asked Questions (FAQs):

How long can a generator sit without use?

If you add a properly formulated fuel stabilizer and store your generator in a cool, dry place, the gasoline in the fuel tank has a maximum shelf life of up to one year.

Will a generator start with old gas?

Stale fuel in your generator is likely to cause starting problems due to debris buildup inside the unit. Drain your generator regularly to maintain it properly. Your generator should always have fresh, stabilized gas.

How do you reactivate a generator?

Connect F+ to the positive pole of the battery. Hold the wire F- by the insulated part of the wire, touch F- to the negative pole of the battery for about 5–10 seconds, then remove. Reconnect F+ and F- to the regulator.

Why is the generator not coming on?

One of the most common reasons why a generator will not start is a battery failure. This can often be caused by a loose connection or sulphation.

What can destroy a generator engine?

Excessive heat can have various reasons, such as generator overload, faulty winding insulation, or insufficient bearing lubrication. Overheating a generator will shorten its life and if the problem is not resolved quickly, it will destroy the generator completely.

How long can a generator run without damage?

On average, a standby generator can run up to 3,000 hours to power an average home, although it is recommended not to run the generator continuously for more than 500 hours.

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