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Generator Starts But Won’t Keep Running? Here’s Why

Generator Starts But Won’t Keep Running? Here’s Why

Having lived through multiple hurricanes, I realize how critical it is to have a reliable generator. Without proper maintenance, you may find your generator starts but won’t idle or carry a load without dying. Here’s what I’ve found from my experience.

If your generator starts but won’t keep running, here are two likely issues to check:

  • make sure that it’s not overloaded
  • check for fuel or air delivery obstructions

A clogged air filter, vapor lock, or dirty carburetor often cause this issue.

Read on as we delve into the reasons why overheating or a problem in several components of the generator’s fuel system can stall your generator, as well as other reasons why this issue crops up and, most importantly, how to fix these problems.

Reduce the Load if It’s Overloaded

If your generator has a circuit breaker, it will stop working when you work your generator above capacity (source). If it doesn’t, it runs the risk of overheating and might be a fire hazard because gasoline is flammable.

How Do You Know if You’re Overloading Your Generator?

When you have had your generator for a very long time, you will be familiar with how it sounds and immediately know if it doesn’t sound right. But there are sure ways to tell if you’re overloading your generator if you are not sure.

The first is overheating. Because the generator is running fans to cool itself double time, your unit is overworking itself. Also, the power output might be reduced in an overload (source). So your generator is not only working doubly hard, but it’s also working more for lower power output.

Further, you can check the exhaust. If you are overloading your generator, there will be leftover soot in that area.

Why Overloading Can Stall Your Generator

Aside from the circuit breaker stopping your generator when it’s getting too heated, there are other reasons why overloading can stall your generator. 

According to this Welland Power, there are also times when overloading can cause your generator’s engine speed to decrease and shut down, which is when you plug in a load bigger than the generator’s emergency standby power rating (source).

Normally, your generator will slow down when you load something, but it usually goes back up. But if the load is too big, it might not go back to its normal speed.

Here are some of the things you can do to remedy overloading:

  • Ensure that the generator is installed properly, and sometimes you may need a professional to do the installation for you.
  • Do not go beyond your generator’s output rating, which means you should be using fewer appliances and plugging in only the essentials.
  • Make sure that you do regular maintenance on your generator regularly. To do this, consult the owner’s manual and check out the manufacturer’s suggestions on keeping your generator in top working condition.


Check to See if Your Generator Is Getting Enough Fuel

If it’s a one-time thing, you might want to fill up the gas tank. Your generator might be low on fuel, which is why it stopped midway. But if the gas tank is full and your generator still stalls and stops, here are some of the things you can do.

One thing that can stall or stop your generator is when it has problems getting enough fuel. Here’s how you check if it’s a problem with the fuel filter or the fuel pump:

A SIMPLE Onan Generator Fuel Pump Test and Replacement Tips

Change the Fuel Filter

There are times when fuel is restricted because of a bad fuel filter and your generator cannot get enough of it to continue working.

According to Car Bibles, a failing or bad fuel filter will result in fluctuating power, engine misfire, or stalling. Your generator will exhibit the same symptoms.

You can still start it because of the gasoline that remains in the fuel line, but once this is burned, your generator will stop working.

Changing the fuel filter can stop this problem. And here’s how you do just that:

Open the Fuel Valve

The fuel valve regulates the flow of fuel into proper channels. If it’s closed, your generator will not start at all. But if your generator stops running after a while, it might be due to a clogged fuel valve that might be preventing enough fuel from getting into the engine. 

You can replace the fuel valve by following the steps on this video:

Replace or Clean a Clogged Fuel Pump

Fuel injectors can clog up and block fuel from moving through the combustion system, causing several problems such as having difficulty when starting or when running on load. It can also result in increased fuel consumption or leaking fuel (source).

Here’s how you test, gain access to and replace a fuel injector in a diesel generator:

Diesel Generator - Fuel Injector

If you want to try cleaning the fuel injector you can get some cleaner such as the Gunk PCD14T Instant Parts Cleaner & Degreaser (link to Amazon) and some generic plastic tubing and follow the steps in this video:

How to clean fuel injectors on a budget.

Clean the Carburetor if It Is Clogged

A clogged carburetor is one of the likeliest causes of your generator stopping after a few minutes of operation. The carburetor can get clogged or it may have sticky and gummy fuel in the float bowl. This usually happens when you leave fuel in the engine for quite some time.

Some fuel components will evaporate over time and what remains is a sticky and thick fuel that can clog up the ports and jets inside the carburetor. This, in turn, will lead to problems with the engine’s operations.

You will need to drain the float bowl and clean the carburetor with a product like Berryman Products Chem Dip Carburetor Parts Cleaner (link to Amazon). Carburetor cleaners can help you get rid of gummy fuel, grease, sludge, and hard carbon. As such, it can unclog a carburetor in no time.

You may need a Carburetor Repair Kit (available through amazon or local stores) to replace gaskets, etc.

If cleaning your carburetor doesn’t keep your generator running, you might need to replace it.

Purchasing and installing a new carburetor (link to Amazon) can improve engine performance. They are relatively inexpensive and personally I would rather just replace a generator carburetor than take one apart, clean and rebuild. 

Still, cleaning is a cheaper option and if nothing else, it’s a good troubleshooting step to ensure that you have actually found the source of the issue.

This YouTube video explains some of the issues that the carb may be causing and how you can clean it.

A Quick, but Temporary Fix

If you are in a bind and your generator acts up and you suspect that it has something to do with the fuel system you may be able to get it running with Sea Foam (link to Amazon).

I have become very fond of this product and tend to use it in all of my small engines.

Using products like these can help if the problem is old and gummy fuel. However, you will still need to clean the carburetor, fuel filter, and other affected components at some point.

Clean the Air Filter

Like a bad fuel filter, dirty air filters can cause your generator to stall. While it’s rare, a dirty air filter cannot bring sufficient air to the generator’s engine. It can lead to your generator stopping after a few minutes, or even engine failure.

Cleaning the air filter is very simple. Here’s a video on how to clean your generator’s air filter:

Prevent Vapor Lock

Vapor lock happens when the fuel you use in your generator overheats and vaporizes too quickly (source). It produces gas bubbles that can block the fuel delivery. This, in turn, stalls your generator and it will not restart until the engine has cooled off.

To remedy vapor lock, you need to make sure that you only put in fresh fuel into the tank, and use a fuel stabilizer as much as possible. You should also ensure that you use the right grade oil and clean the fuel filter.

Vapor lock can also happen if the air intake and cooling fins are dirty, or when it’s too hot outside.

Other Solutions

Other than these solutions, here are some more things that you can try:

  • Make sure there is enough engine oil. With low oil levels, you might be able to start your generator, but it will sputter and die when the oil heats up and forces the system to shut itself down. This is a feature built in to protect the engine.
  • Replace a fouled spark plug. While a bad spark plug often results in your generator not starting, it can sometimes lead to your generator running only for a few moments and then shutting down. Clean or replace the spark plug if this happens.


It’s possible that your generator won’t keep running due to a fuel or air delivery system issue. But overloading is a common issue with a simple fix so before you start taking it apart, try unplugging some unnecessary devices and see if that solves the problem.

If it does, then try plugging in devices one by one to ensure a reasonable load.

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