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Why Does My Generator Shut Off After 20 Minutes?

Why does my generator shut off after 20 minutes
Written by Jamie Masterson

There’s nothing worse than your generator shutting off. You’re probably already without power, and now you have to witness your back up die in front of your eyes. A generator is made up of a lot of parts and any of those parts malfunctioning can lead to the generator shutting off after 20 minutes. Luckily, many of these fixes are easy and can get your generator running again in no time.

In this article, we’ll be looking at the causes and solutions for a generator that shuts off after 20 minutes. Let’s get into it.

What’s Causing it and How do I fix it?


Generators are built to take on a specific amount of load. If your load exceeds the generator’s capability, you will cause it to overload. Most modern generator brands come with a built-in, automatic kill switch to prevent the generator from exploding. Overloading is not only dangerous, but can ruin the inner parts of the generator, leading to some expensive repair bills.

If your generator is shutting off after 20 or 30 minutes, there’s a good chance that your generator could be working too hard. The best thing to do is to take note of your generator’s power capacity. The capacity will be measured in kilowatts (kW). Once you have that, test the power usage of your appliances that the generator is powering. If it exceeds the generator capacity, remove anything you don’t absolutely need. High wattage appliances like fridges, ovens, and microwaves should never be powered through a generator.

Carburetor blockage

When the fuel is converted to energy to power the generator, some leftover residue will start to build up in the carburetor. While it is not directly harmful, this residue can build up and thicken, leading to the fuel being blocked from getting to where it needs to go for combustion.

If the fuel can’t get to the engine, then the generator will shut down. Fuel needs to be running through the generator at all times. If it doesn’t, the generator will have trouble running without anything to produce energy. To fix this, detach the carburetor from the generator and clean with a cleaner. These cleaners are sold in hardware stores and will eat away any residue without damaging the carburetor. You may need to push out any stubborn bits, but that can be easily achieved with a rag and long, thin tube.

Oil sensor malfunction

The oil sensor in a generator keeps track of the oil levels in the engine. It will notify you when the oil level is low and will prevent the engine from starting. Sometimes, there can be a malfunction in the sensor where it will fail to give the warning or report that the oil is too high.

Finding out if you have a faulty oil sensor is a lot of work but it can save you money and time. You’ll need to open the generator, adjust the wiring, then run the generator to see if its working.

The oil is low

Engine oil is a delicate balance. If the oil is too high, the engine will shut off because the oil sensor will send a warning. If the oil is too low, the engine temperature will rise quickly and overheat the engine. The engine will then shut off.

Before starting your generator, check the oil by using the oil rod in the pan. There should be a line that tells you where the oil level should be. The oil can go down a little, but it really shouldn’t be too far down the line. While you’re checking the oil level, look at the color of the oil to see if it’s too dirty.

Problem with the fuel line

When there isn’t enough fuel flowing into the engine, the engine will shut off. Combustion needs to be consistent for the generator to run properly. The fuel lines are the main way that fuel enters the engine. If these are clogged, then fuel is prevented from flowing into the carburetor. Damaged fuel lines can lead to leaks that drain the fuel before it even gets used. Lastly, if there is moisture in the fuel line, the fuel can get contaminated, changing the chemical compound of the fuel. All of these things will prevent your generator from starting.

The fuel lines are located near the air filter and carburetor. Before you remove them, make sure they are clearly labeled. If you attach the wrong line into the incorrect position, you can destroy the engine. After removing the fuel lines, gently clean them and let them dry completely. Re-attach them and turn on your generator to see if it runs more than 20 minutes.

Dirty air filter

Like dirty fuel lines, a dirty air filter risks contaminating the fuel. Particles in the air filter can get stuck in the fuel, causing the fuel to become dirty. This leads to fuel inefficiency and can cause the engine to shut off. Another risk with a dirty air filter is air flow. Air needs to be flowing through the engine to keep the temperature normal and assist with combustion. If the engine gets too hot, it will shut off automatically.

Luckily, replacing an air filter is easy and cheap. Remove the air filter from its case and replace it, then test the generator. Once air flow is back to normal, the engine should be able to run ok.

The water level is too low

Temperature is one of the most important aspects of a generator. High temperatures can lead to engine failure. That is why some kind of coolant is needed to keep the engine’s temperature at a workable level. If the engine is too hot, the generator won’t run for very long before shutting down.

Check your generator’s coolant or water levels to make sure they are topped up. The water needs to keep everything nice and cool. Without it, the engine won’t run very long before it overheats. Once you’ve topped up the water level, the generator will run at normal temperature and won’t shut off.


Q. Why does my generator die under load?

A generator has a specific amount of power it can run. Any amount over the limit will make your generator overload and die.

Q. How do I keep my generator running without stopping?

Your generator should be run under load for between 15 to 30 minutes at least once a week. This will act as short-term maintenance for the generator. When you’re doing this, check all of the fluid levels and the condition of any open parts.

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.

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