Skip to Content

6 Reasons a Generator Bogs Down Under Load (Troubleshoot)

When the air-to-fuel mixture isn’t right or you try to power more than your generator can handle, it may begin to run sluggishly and bog down.

Generators bog down and lose power under load when too much load is applied for the size of the generator, the carburetor is dirty, the fuel filter is clogged, the air filter is plugged, the choke is stuck, or the spark arrestor is plugged.

Wait for the engine to cool and remove the spark plug wires before performing any repairs. Follow this in addition to the safety precautions outlined in the operator’s manual to minimize serious injuries.

Generator bogs down under load

This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.

Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Troubleshoot a Generator Bogs Down or Shuts Off Under Load

1. Too Much Load is Applied for the Generator Size

Generators don’t have the same capacity. There are limits to the wattage a generator is able to handle. When you exceed this limit, the generator can bog down.

This will not only cause your generator to run sluggishly but also can cause potential damage to the generator and the items connected to it.

Before checking the generator for items that can cause it to run rough, check the load limit of your generator along with the wattage requirements of the items you are running with the generator.

The wattage requirements of the items you are running at the same time must be less than the generator’s load limit.

The load limit is often printed on the generator or you can find this information in your operator’s manual.

You may also find a starting wattage limit that will temporarily allow for a greater load when powering items that require additional wattage for a few seconds to start the motor.

Follow these tips to determine the wattage capacity:

  • You will find the wattage of most electrical items listed on a tag attached to the item.
  • Some motors require additional wattage to start an item. In this case, the starting wattage should be used when calculating wattage requirements.
  • Add the wattage of all items that will be plugged into the generator at one time to get a total.
  • This total wattage must be less than the generator’s wattage capacity.

Do not run more electrical items using the generator than it can handle. When the unit bogs down, shut down the generator. Remove all items plugged into the ports. Restart the generator and add one item at a time.

2. Dirty Carburetor

Old gas leaves varnish and sticky deposits in the carburetor. Varnish is a result of old gas that will coat the internal parts of the carburetor causing fuel passages to become plugged.

Without sufficient fuel, the fuel and air mixture will not ignite to form the explosion needed to start the engine. A dirty carburetor will need to be removed to be cleaned or rebuilt to get working again.

To clean the carburetor, it’s a good idea to take photos through the disassembling process to make sure the small parts are placed in the correct positions when reinstalling the carburetor.

Remove the carburetor from the generator. Remove as much buildup as you can using a carburetor cleaner. If you find any damaged parts, use a carburetor rebuild kit to replace them. Once cleaned and repaired, reinstall the carburetor.

If working with small parts is not something you want to tackle, you can purchase and replace a complete carburetor instead of tearing it apart to clean and rebuild it. You may need a new carburetor if it still doesn’t function after cleaning it.

3. Clogged Fuel Filter or Sediment Bowl

A fuel filter is used on a generator to keep dirt from finding its way through the fuel system to the engine causing wear and damage.

You may have an inline filter placed between the fuel lines or you may have a fuel filter installed at the bottom of the fuel tank. You may also find a fuel sediment bowl on the fuel shut-off valve.

It’s best to replace the fuel filter and clean the sediment bowl (if your model has a sediment bowl) each year when you are running your generator like most homeowners.

If you use it more regularly, you must complete this maintenance more frequently.

If you are unsure if a fuel filter is used and where your fuel filter is located, contact your local generator dealer or the manufacturer’s customer support line for assistance.

4. Plugged Air Filter

The air filter keeps dirt from entering the air intake to protect the engine from the damage that can occur from just a small amount of dirt or debris.

Just like the fuel filter, you should replace the air filter at least once a year and more often if you use the generator frequently or are operating it in dusty conditions.

In addition to replacing the air filter, you must also keep it clean. This includes checking the filter several times in between replacing the filter to ensure that the filter is kept in good condition and free of dirt and debris.

If you are not cleaning and replacing the filter regularly, the filter can become plugged with so much dirt that the engine won’t get sufficient air. It can cause the engine to bog down, overheat and cause extensive permanent damage.

Check the air filter before each use and clean or replace it if needed. Follow the cleaning instructions found in the generator operator’s manual.

I have included cleaning instructions for a couple of types of air filters below. Consult your manual if you are unsure of how to clean your type of air filter.

Clean a generator FOAM air filter

  • Remove the air filter from the housing.
  • Wipe out any dirt remaining in the air filter housing and cover. Don’t allow dirt to fall into the air intake.
  • Inspect the foam filter for damage and replace it if needed.
  • If the filter is in good condition, clean it in soapy water and rinse it until the water runs clear.
  • Squeeze the filter and allow it to dry.
  • IF THE FILTER WAS COATED IN OIL, once dry, coat the filter with clean engine oil. Squeeze to remove excess oil. Not all foam filters are coated in oil. Refer to your operator’s manual if you are not sure whether to add oil to the filter.
  • Install the air filter.
  • Reattach the air filter cover.

Clean a generator PAPER air filter:

  • Remove the air filter from the housing.
  • Wipe out any dirt remaining in the air filter housing and cover. Don’t allow dirt to fall into the air intake.
  • Inspect the paper air filter. Tap the filter to loosen dirt so it falls from the filter. If the filter is very dirty, damaged, or no longer seals the air intake sufficiently, replace it with a new one.
  • Install the air filter.
  • Reattach the air filter cover.

5. Stuck Choke

Another lack of airflow problem that can cause the generator to bog down is when the choke isn’t adjusted after the engine warms to allow sufficient air to get to the engine.

This can be due to forgetting to adjust the choke to the off position once the engine warms. It may also be caused by a bad switch or dial (depending on your model) used to start the generator or a stuck choke.

6. Clogged Spark Arrestor

The spark arrestor screen is a part installed on a generator to prevent sparks and hot material from emitting from the muffler. This is to reduce burn injuries and potential fires.

When this metal screen becomes plugged with a buildup of carbon, the generator will begin to run rough and possibly shut down because hot exhaust air is unable to leave the engine.

Before removing and cleaning the spark arrestor, wait for the muffler to cool to reduce injury. Remove the spark arrestor screen and inspect its condition. Replace the screen with a new one if you find any tears or holes in the mesh screen.

If the screen appears to be in good condition, clean it with a commercial solvent or brush it lightly using a small metal brush to remove soot deposits. Once the screen is clean, place it back onto the muffler.