How to Change a Generator Air Filter

Your Generator’s engine uses air for combustion. The air filter removes dust and foreign particles from the air taken into the Engine. Dust is abrasive to engine components. If let to pass through, it will corrode the piston rod, valve gear, and cylinder. You will soon start to pay more for fuel since the efficiency of the generator is reduced.

Generators have two types of air filters; Foam and Cummins Onan filters. Replacing them increases the lifetime of your generator while reducing running costs. This article explains how to change a generator air filter.

Tools required

  • Screw Driver

How to Change a Generator Air Filter

  • Electricity Current Tester

Materials Required

  • New Paper or Foam air filter. Refer to your generator’s manual for spare parts specifications.
  • Oil
  • Gloves
  • Goggles

How to Change a Generator Air Filter

  • Detergent or Non-flammable solvent.

 How to Change a Generator Air Filter (Foam/Paper filters)

Before carrying out any maintenance on your generator, ensure it’s been inactive for at least 24 hours. Unplug it from any mains or outlets. Turn off the valve to prevent fuel from flowing to the carburetor.

Step 1 – Disconnect the Spark Plug

Locate the spark arrestor and disconnect the spark plug. This prevents the Generator from starting due to static electricity. Refer to your generator Manual for its precise location. The Manual may include precautions or specific instructions on how to do so. If not, rotate the spark plug gently until it’s disconnected from the spark arrestor. Pulling will strain it.

Step 2-Test for current

Place your finger on the metal tip of the tester and tap the metal parts around the spark plug. The bulb inside the tester should not light up. Otherwise, there’s still current flowing into or out of the generator. In this case, you should unplug any cables connected to the Generator.

Step 3-Expose the Air Filter

While referring to your Generator’s manual, locate the Air filter Metal or plastic housing. In most cases, it’s at the back-left-hand side. If its metal housing, unscrew the housing with the correct screwdriver to avoid corroding the screw heads. For Plastic housings, Unclip or unclamp the housing from the generator.

This will expose the foam or paper filter covered with grilled or grated metal plates. The filter or grilled plates may be fastened to the edges with a rubber hose depending on the manufacturer. In models like Caterpillar (CAT) and Champion, the filter is simply placed in the housing. Use a pair of pliers to slide the housing edges off the rubber hose. Clean it using detergent and let it dry.

Step 4- Extract the Foam Filter

Using the correct Flathead or screwdriver, unscrew the plates. Do this while in gloves as the foam filter and grill plates will be oily and the paper filter extremely dusty.

Extract the air filter from its housing while referring to the Manual. Place the grilled plates on a metal or iron surface so that dust or grime will not accumulate on them. Dispose of the old filter.

Step 5-Lubricate the new filter

If your generator uses a foam filter, dip the new filter in the oil to moisten it. Clean the Grilled/grated plates with a detergent. Dry them before dipping them in the oil. Wipe off excess oil from the grates to prevent staining the rest of the Generator.

Step 6- Install the new filter

Slide the new filter into the grilled housing. Screw the housing onto the generator while taking precautions to avoid corroding the screw heads. Replace the rubber hose fitting it using a screwdriver with a rounded tip. Ensure the filter is fastened correctly. The combustion chamber is under high pressure making the carburetor suck the filter if loosely fitted. This will knock your Generator’s engine.

Step 6 – Cover the new filter

Wipe off excess oil before replacing the external metal cover. Screw the cover to the generator and plug in the spark plug and its cover. You have changed your Generator’s Air filter. Power on your generator and check for the engine sound. If the replacement was successful, the engine should sound normally.

How To Change Cummins Onan Air Filters

Step 1 –Disconnect the Spark Plug

Refer to your Manual and locate the Air filter and spark plug. Disconnect the spark plug from the spark arrestor. This will prevent the generator from stating from static electricity build up.

Step 2 – Uncover the Air Filter

Depending on the brand and purpose of a Generator, it may be housed with a plastic or metal casing. The Plastic Casing is screwed in using a long, threaded screw.

Turn it in the anti-clockwise or clockwise direction depending on your manual’s instructions. For the metal casing, use a flathead to unscrew the casing. Pull out the Screw and remove the plastic casing. The Filter will be housed inside a metal holder about the same width as the filter itself.

Step 3 – Extract the Air Filter

Unmount the housing and pull out the Used up filter. Dispose of it following guidelines from your manual. Careless disposal may be illegal in some states due to environmental regulations.

Step 4 – Install the new filter

Clean the housing using a detergent and let it dry. Fit the new Cummins Onan Air filter into the housing. You need to confirm from your manual which models are compatible with your generator. Ensure the filter fits exactly in the housing. Mount the housing to the generator and fasten the screws. Do not overtighten. Replace the plastic or metal cover. You have changed your Cummins Onan Air filter.


Your generator’s air filter needs to be replaced after 100 hours. Otherwise, the valves, pistons, and cylinders in the engine will be corroded. Changing or cleaning your generator’s air filter increases its lifetime.

Always refer to your generator’s operation manual before any servicing. Before disposing your used air filter, check with your state’s environmental and e-waste disposal guidelines.

Faqs About Changing Generator Air Filter

How do you power a generator filter?

The generator filter does not require power. Once installed, the filtering process does not run on any power; just pressure difference.

What is a fuel filter in a generator?

Fuel filters clean fuel passing onto the engine. There are Refuel filters and secondary filters. Depending on the model, they can be located together or in different positions.

What are the main parts of an electric generator?

How to Change a Generator Air Filter

  1. Engine
  2. Battery Charging system
  3. Fuel intake system
  4. Control Panel
  5. Alternator
  6. Cooling system
  7. Exhaust system
  8. Main Assembly Frame.

How many Filters does my generator have?

Your generator has three filters: an air filter, a Fuel Filter, and an Oil filter.

What are the types of Generator air filters?

  1. Paper filters.
  2. Foam filters.
  3. Fiber Glass filters.
  4. Gauzed Cummin Onan Filters.

Does removing the air filters increase generator power?

No. Removing your generator’s air filter will drastically reduce its power output and lifetime. Foreign particles in the air used by the engine for combustions cause wear and tear; reducing its efficiency.

What happens if your air filter falls off?

Foreign particles will get into the generator causing wear and tear in the engine parts.

How often should you change the fuel filter?

You should replace your fuel filter after 500-1000 hours of use. This will depend on your brand and type of filter (Electromagnetic or cylinder).

How long does a spark plug last in a generator?

200 hours. You should replace the spark plug after this duration.

What are the signs of a dirty air filter?

Unusual engine noises and reduced power output. Your generator will start to break down frequently and consume more fuel.

What happens if an engine gets too much air?

Your generator will fail to power on. Too much air will affect the air density in the engine. The combustion functionalities will be compromised hence it will constantly break down or fail to start.

Does a Generator have an Air Filter?

Yes. The engine has an air filter to clean the air circulating in and out of the generator. The air is used for combustion.

Can you run a generator without an Air filter?

Yes, but it will break down. The engine will be circulating air containing dirt and debris that will corrode the valves, pistons, and cylinders.

How Can I Clean My Cummins Onan Air Filter?

After removing the filter from the housing, spray the gauzes with an Air filter cleaner. Let the cleaner soak then rinse with warm water. Air it out to dry.

Alternatively, you can blow it with air compressed under high pressure.

How do you clean a Generac air filter?

After removing the air filter, soak it in a detergent or non-flammable solvent for 2 minutes. Alternatively, blow the paper or foam filter with compressed air to remove trapped dust and debris. Rinse and wring it gently to drain the detergent or solvent. Soak it in oil and drain the excess. Your Air filter is now clean.

How often should you change your generator’s oil?

You should change your generator’s oil after 500 hours. However, servicing of smaller diesel generators should be done after 100 hours.

Where is the air filter on a generator?

The air filter is located at the back-left side of your generator. You should however refer to your generator’s manual.

How do you remove an air filter from the generator?

  1. Locate its position using the Generator’s servicing manual.
  2. Unclip or unclamp the cover to expose the air filter.
  3. Extract the Air filter. If it’s housed in metal grills or grates, Unscrew the grill housing and extract the Air filter.

Where can I get new Air filters for my generator?

You should refer to your generator’s manual for specifications about compatible air filters. They can be bought from the manufacturers or a genuine spare parts dealer.

What’s the difference between a Cummins Onan Air Filter and a Foam Air filter?

A Cummins Onan filter uses a gauzed can to filter debris from air. The foam air filter uses a spongy material dipped in oil to trap dust particles and debris.

Check out this video

About Steve Stuart

Steve Stuart is an electrical engineer who developed interest on generators during his school years. After school, he became a generator enthusiast. This is after encountering power supply problems at the area of residence where he lived. Power would be on and off and so food would go bad and the room heater would go off especially during winter. After trying the different generator brands for several years, Steve now provides information on the available brands and products in the market today. Based on his experience, he gives the do’s and the don’ts when it comes to generator use.

Leave a Comment