Should Your Lawn Mower Fuel Filter Be Full?

Lawnmowers have three filters to prevent dust and debris from getting into the engine. These parts include an air filter, fuel filter, and oil filter. The fuel filter is in line with the fuel pump that sends the gasoline to be burned in the combustion chamber. However, these filters are encased in a plastic housing that sometimes pulls air inside.

Your lawnmower fuel filter should be full to prevent air from entering the combustion chamber through the fuel line. If air enters through the fuel filter, the lawnmower’s engine will burn the fuel incorrectly, causing overheating and smoke. Bleed the line to remove excess air from the fuel filter.

Small air bubbles won’t ruin the combustion chamber as long as they stay in the fuel filter. You might notice a small gap above the filter, which is normal. A lawnmower’s fuel filter needs to be almost completely full to encourage the proper fuel pressure and oxygen: fuel ratio for proper burning rates. Let’s discuss everything you should know about lawnmower fuel filters today.

Suggestion: A leaky fuel line can prevent the filter from filling as it should. If your fuel line is leaking, it might be time to find a lawnmower filter line assortment kit on Amazon or at your local hardware store. Make sure it’s the right diameter to prevent looseness.

Why Should a Lawn Mower Fuel Filter Be Full?

A lawnmower fuel filter should be full to improve the fuel’s pressure and efficiency in the combustion process. A half-full filter indicates there’s not enough fuel going to the chamber. It could also mean it’s time to add more fuel to your lawnmower, which is an easy fix.

Here’s what will happen if a lawnmower’s filter isn’t full:

• The fuel won’t burn quickly with the oxygen entering the combustion chamber. Perhaps the most obvious symptom of a bad fuel filter is that the engine starts overheating because it’s burning too much oxygen and not enough gasoline. Keep in mind that battery-powered mowers work differently.
• Your mower will be much louder than it used to be. The engine starts working a lot harder to pull more fuel from the tank, but the half-full fuel filter won’t budge. It’ll keep pulling air rather than gasoline, causing the engine to smoke and roar.
• The lawnmower will underperform if the fuel filter isn’t full enough. Since it’s not getting the fuel it needs to operate, it’ll likely be slower, it won’t cut as fast, and you’ll have to push much harder to make it move. Riding mowers can get a bit bumpy if this issue occurs.

Without a doubt, lawnmower fuel filters need to be full of fuel. It might seem obvious, but knowing the proper levels can be a bit confusing (especially since it’s okay for a small bubble to sit at the top portion of the filter). As a general rule, there shouldn’t be any air pockets touching the filter or either line.

How Do I Know if My Lawn Mower Fuel Filter Is Clogged?

You’ll know if your lawnmower’s fuel filter is clogged if there’s a leak around the filter’s gasket, if the filter looks dirty through the see-through housing, or if your lawnmower is overheating. The fuel filter gets clogged when it’s old and needs to be changed because it’s removed a lot of particles and other contaminants.

Follow these steps to know if your lawnmower fuel filter is clogged:

1. Turn off the mower’s engine if it’s performing differently than usual, smoking, getting too hot, or making loud sounds. These are all signs of a clogged fuel filter, tank, pump, line, or combustion chamber.
2. Let it cool down, then remove the spark plugs to prevent various electrical issues. While it’s highly unlike you’ll encounter these problems since you’ll be working on the fuel line, it’s worth getting in the habit of turning off the engine and remove the spark plugs.
3. Inspect the fuel filter and its housing for excess debris, leaks, swelling, or discoloration. A fuel filter on a lawnmower typically looks white or yellow, depending on which one your mower uses. If it’s clogged, the housing might swell or leak from too much pressure.
4. Remove the fuel filter from its housing a wipe it with a glove or towel. Look for grime, dirt, dust, and other debris. The fuel should be the exact color of the gasoline you poured into the tank. If it’s not, the fuel filter is likely clogged and needs to be cleaned or replaced.

These four steps are a surefire path to knowing if it’s time to fix a clogged fuel filter. A clog can be quite frustrating, but thankfully, it’s one of the easiest repairs you can perform on a lawnmower. The short replacement process takes less than five minutes and can save the mower’s combustion chamber and fuel line from bursting.

Remember, not all overheating is caused by the fuel filter. They’re sometimes caused by the lawnmower’s oil problems.

Why Is My Lawn Mower Fuel Filter Not Full?

Your lawn mower’s fuel filter isn’t full either because there’s not enough fuel in the tank or there’s too much air in the fuel line. If you notice the mower’s fuel filter is empty, turn off the ignition, fill the gas tank with the recommended type of fuel, then start the ignition.

If there’s a leak in the fuel line, it’ll slowly spill fuel on the lawn. It’s one of the many reasons your lawn might smell bad, but it can also cause a potential hazard for the yard if a spark hits the fuel.

To learn when it’s time to refresh or replace the fuel filter, read on.

Do You Need to Clean a Lawn Mower Fuel Filter?

You need to clean a lawnmower’s fuel filter if it’s made of metal, but paper or nylon fuel filters need to be replaced. They’re not reusable, which means you’ll have to clamp the line and remove the filter. To clean metal fuel filters, spray them gently with water until the grime is gone.

Keep these tips in mind when cleaning a lawnmower’s fuel filter:

• Only clean metal fuel filters since plastic, paper, and nylon air filters can’t be reused. Much like your lawnmower’s air filter material, the paper on the fuel filter isn’t designed to be washed a used repeatedly. Once it’s done, it’s time for a new one.
• Metal fuel filters can be gently washed with water, but make sure you don’t use a high-pressure hose. Pouring water over it with a bucket is often enough to remove excess debris and bring it back to working condition. You can also wipe it with towels to prevent rust or leaching water into the combustion chamber.
• Don’t forget to clean the fuel lines and filter housing. They can contain quite a bit of contaminant that clogs the fuel filter, making it overheat. Blow the line out with a high-pressure hose after detaching it from the lawnmower completely. Since mower fuel lines are so inexpensive, I suggest simply replacing them when you notice a clog.

According to Gold Eagle, a lawnmower’s fuel filter should be replaced every eight to ten years. However, it’s a good idea to inspect the line annually and whenever you notice irregular sounds, smells, smoking, and uneven mowing.

How Often Should You Change a Fuel Filter on a Lawn Mower?

You should change the fuel filter on a lawnmower every 200 hours or when it looks grimy and covered in debris. While the 200-hour marker is a good reference point, all clogged fuel filters should be replaced, regardless of how long they’ve been used. A clogged filter can overheat the mower’s engine.

Replace your mower’s fuel filter with this method:

1. Turn off the lawnmower’s ignition to prevent the fuel from flowing through the fuel tank, line, and filter.
2. Clamp the fuel line about two inches away from the fuel filter’s entry point with the 8MileLake Hose Clamp Pliers (or similar hose clamping pliers).
3. Slide both clamps off of the top and bottom of the fuel filter.
4. Pull and wiggle the line off of the fuel filter housing, then remove the filter.
5. Place a new filter in the housing, ensuring it’s the proper size as recommended by the manufacturer’s guidelines.
6. Slide the slamps back onto the top and bottom of the filter housing, tighten them, and remove the clamp pliers.
7. Turn on the engine for 45 seconds to move the fuel through the filter, turn it off, then turn it on again for the same amount of time to drain all of the air out of the line.

As you can see, this process is quite simple and effective. You need fuel filter line clamps or pliers and a regular wrench or set of pliers to remove the filter line clamps. Only two tools to replace the filter? Not bad!

For an in-depth video guide of this method, check out this tutorial by Briggs & Stratton:

Wrapping It Up

A lawnmower’s fuel filter should have more fuel than air. A couple of bubbles won’t cause too many problems, but it’s best to remove as much air from the fuel line as possible. When you’re installing the fuel filter, make sure you clamp the line to prevent the fuel from draining. Turning the ignition on and off a few times will prime the fuel filter line.