Should Lawn Mower Fuel Filters be Full?

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A fuel filter strains the fuel before it reaches the carburetor. Its purpose is to keep dirt and other particles from getting into the engine. Because the filter plays such an important role you have to make sure that it is properly configured. This brings up the question of whether the fuel filter has to be filled or not.

Lawn mower fuel filters have to be filled so air does not get into the combustion chamber. Air will cause the engine to overheat and misfire. If the filter is only half full, there also won’t be enough fuel for the engine.

The mower fuel filter is situated right along the pump that transmits gas into the combustion chamber. The filter has to be full so the engine burns fuel properly. If it is not filled or the fuel line leaks, your lawn mower will not start correctly, if at all.

Why Should You Fill Lawn Mower Fuel Filters

If the fuel filter is partially empty, fuel efficiency is reduced. There will not be enough fuel in the combustion chamber and this will negatively affect how your lawn mower works.

There are many problems that can arise from a half empty fuel filter. The most obvious is the lawn mower runs poorly. The blades do not cut smoothly, the engine stalls or smokes and requires more effort to start. Both push and rider mowers handle poorly with a half filled fuel filter.

Another sign of a half empty fuel filter is the loud noise. Your lawn mower will be noisier than usual because the engine is trying to draw more fuel but all it gets is air. The end result is a noisy, smoky engine that keeps stalling. This can affect all kinds of models including the Craftsman M105, so fix it as soon as possible.

The engine will also overheat and smoke due to lack of gas. Lawn mowers must have a specific gas and oil ratio to burn correctly. If the fuel filter is lacking, the ratio will be off and cause problems.

Why Your Lawn Mower Fuel Filter is Not Filled

There are two reasons why this can happen: the fuel line is full of air or there is insufficient fuel to power the engine.

Turn off your lawn mower and look inside the tank. If there is not enough fuel, fill it up according to the manufacturer’s instructions. Turn on the mower and everything should be fine.

If the problem is a leaking fuel line, it has to be replaced. You can do this yourself or take your mower to a service center.

Related to this is the problem of the fuel filter emptying quickly. For example, you fill the fuel filter, but after running your lawn mower for 15-20 minutes, it empties out.

If this happens, turn the mower off and clean the carburetor. If that does not work, remove the filter and reinstall it. You may have installed it incorrectly.

An incompatible fuel filter might cause this problem too. Some lawn mowers will only work with specific types of filters, and so-called universal models may not work. Just as spark plugs are not universal some lawn mowers prefer a particular filter.

Image Credit: Hedwich Storch

Signs of a Clogged Fuel Filter

The most obvious sign is a leaky fuel filter. But there are other indicators even if you don’t look at the filter itself. An overheating engine, poor performance or stalling engines are common indicators.

Engine problems can also be due to a faulty spark plug or something else, so the best way is to look at the fuel filter itself.

To find out if the filter is clogged, observe your lawn mower. Is it louder than usual? Is it overheating or there is smoke? If the answer is yes to any of these, turn the mower off.

Give the engine time to cool down and take off the spark plugs. Whenever you do any type of lawn mower troubleshooting, it is best to remove the spark plugs as a precaution.

Examine the fuel filter thoroughly. If it is dirty and leaking it will be very obvious. If it looks larger than when you installed, it is probably filled with debris and grime.

Remove the fuel filter so you can clean it. If there is only a bit of dirt, wiping with a piece of cloth will be enough. But if it leaks heavily and/or caked with dirt, follow these cleaning instructions. This method works with many types of lawn mowers including the Power Smart 209cc,.

How to Clean a Lawn Mower Fuel Filter

Cleaning fuel filters is a bit more involved that say, cleaning mower bags. But if you follow these steps you should be done in a few minutes.
You will need socket wrench to detach the fuel lines and protective eyewear to avoid oil spills getting in your eyes.

Step 1. Turn off the lawn mower.

Step 2. Take out the fuel pump fuse. Refer to your owner’s manual for its location. After removing it, allow the engine to run for a couple of minutes. Turn it off.

Step 3. Disconnect the fuel lines using the wrench.

Step 4. Remove the fuel filter. Tap it to remove residue and dirt struck inside. You can use a carburetor cleaning solution or plain water to spray the inside and outside of the filter. Let the filter air dry.

Step 5. Put the filter back on once it is dry, and put everything back in the reverse order of how you took them out.

Should You Clean or Replace Fuel Filters?

Metal filters can be cleaned with water or other cleaning solutions. Fuel filters made of nylon or paper have to be discarded. Once they leak or covered with dirt, replace them with new ones.

Paper and nylon filters are one-time use only but they are cheap and easy to replace. Metal fuel filters can be cleaned and reused. Replace if damaged however.

Your lawn mower manual includes information on what fuel filter it is using. In general though any metal filter is reusable. If there are signs of clogging of blockage, follow the directions given earlier to clean it.

The cleaning method will depend on how dirty the filter is. A piece of cloth will do if there is just a small amount of dirt. For moderate levels of dirt and grime, use water. You can wipe the filter with a damp cloth or place it under running water.

Do not use harsh chemicals or too much water. Unless the filter is really dirty, cleaning will take just a few minutes.

The next question you are probably asking is how often to clean lawn mower fuel filters. The answer is as often as necessary.

If your lawn mower exhibits any of the signs of a dirty fuel filter, clean it or get a replacement. If your mower is running smoothly then the filter is fine. You should still check it when performing lawn mower maintenance however.

When and How to Replace Lawn Mower Fuel Filters

Lawn mower fuel filters should be replaced after 200 hours of use. But you should replace the filter immediately if it is clogged up and the engine is having difficulty running.

If you notice symptoms of a clogged fuel filter, clean it following the instructions given in this guide. If that does not work or the filter is too dirty or damaged, get a replacement.

Follow these steps to replace a lawn mower fuel filter:

Step 1. Turn off the lawn mower.

Step 2. Measure a couple of inches from the fuel filter entryway, clamp the fuel line.

Step 3. Take the line off the fuel casing.

Step 4. Remove the filter.

Step 5. Install the new fuel filter and put the clamps on.

Step 6. Turn on the engine and let it idle for a minute. Shut it off then turn it on again for another minute. This should get rid of any air trapped in the fuel line.

Now you can run the lawn mower normally. With the new fuel filter there should be no more issues with leaks or smoke.