How to Know if Mower Fuel Pump is Bad

Maintaining your lawn mower is key to ensuring its longevity and proper functioning. One of the most critical maintenance tasks is keeping the fuel system clean. However, if you suspect that there might be something wrong with your fuel pump, how can you tell?

This blog post will discuss how to know if mower fuel pump is bad and what you can do about it.

What is a Fuel Pump, and What Does It Do?

A fuel pump is a device that works to transfer gasoline from the tank or storage compartment into your mower engine. As it does so, it creates pressure to push the gasoline through.

Without adequate pressure, your lawn mower cannot function at its best, and you will encounter issues such as reduced throttle response time and bad running performance.

How to Know if Mower Fuel Pump is Bad

If your mower starts but runs roughly, this could be a sign that the pump is worn out or damaged somehow. Here are some signs to look out for:

1. Fuel Tank Noise

One of the most common signs is a fuel tank that seems to vibrate or make noise. This can occur because of a worn-out pump, causing gas to splatter all over the inside of the tank.

The vibration means there isn’t enough pressure to keep it in place, and your mower won’t function properly as more gas is splashing out.

If you notice this issue, inspect the pump and replace it if needed. If your mower still starts but seems to be running rough, then it might also need to have the air removed from its fuel line via a process called “priming.”

2. Priming the Fuel System

When your mower won’t start, and you’ve checked for and replaced the fuel pump, air may be trapped in your fuel line.

This has likely occurred because the gas cap wasn’t correctly closed after refueling, causing gas to overflow and coat the inside of the tank with a film of gasoline.

You will need to remove this excess fuel from your line using the best oil extractor before it can be appropriately primed, and you can get back to mowing the lawn.

3. Sputtering Engine

If you notice that your mower’s engine seems to be sputtering or hesitating when you pull the starter cord, it might mean that the pump has worn out. This issue can occur because of an overflow of gas inside the tank during refueling.

Overfilling the fuel tank will prevent proper suction in your mower’s fuel pump and cause this issue.

The best way to avoid it is to ensure you don’t overfill the tank after each refueling, which can lead to a messy spill if your mower has an older-style cap without a locking mechanism.

After refueling, stop immediately and turn off the motor if you notice this happening. This should give you enough time to check the fuel tank and remove excess gas.

If your mower is still starting but running roughly, it might be a good idea to have the fuel line priming tool ready just in case too much air gets into the system from refilling.

Also read: Can you use synthetic oil in Kawasaki mower engine?

4. Bad or Clogged Filter

If your mower is older, the fuel filter might have clogged up and need to be replaced. This can cause many of the same issues as a worn-out pump – even if it still starts, you’ll notice an increase in noise or stuttering as your lawnmower runs.

However, a bad or clogged filter shouldn’t necessarily mean that your pump needs to be replaced as well.

It’s a good idea to replace any parts that might be defective, but if you notice this issue after just refilling the tank, it could mean your filter is dirty and not much more.

5. Dead Engine

If your lawnmower’s engine is dead or doesn’t even start after being refueled, then it almost certainly means that the fuel pump has failed. This will prevent gas from entering the carburetor and leave you with a useless mower.

In this case, the best thing to do is have the fuel pump replaced as soon as possible. If you have any tools with you, it might be a good idea to check the fuel line for air bubbles or excess gas.

Also read: Can a lawn mower blow up?

symptoms of bad fuel pump on riding mower

6. Power Loss

If you notice your lawnmower’s engine is powering down during use, it could be because of a faulty fuel pump.

This can happen for many reasons, although it shouldn’t necessarily mean that the pump has to be replaced if you haven’t experienced any other symptoms.

7. Surging Power

If you hear your lawnmower’s engine surging and losing power after refueling, this is most likely the result of a fuel pump that has failed.

A bad pump will cause unneeded pressure to build up in your mower’s fuel system and lead to severe problems if it isn’t fixed soon.

Also read: Best riding mower lift jack

Again, it might be a good idea to check the fuel filter or line for excess gas if this happens after refueling.

It could also be a good idea to get your lawn mower serviced at your local small engine repair shop, especially if you haven’t experienced any of these issues before.

Lawn mower makes popping noise

FAQ’s symptoms of bad fuel pump on riding mower

Can a Fuel Pump Be Bad Even If It Turns On?

Yes. A fuel pump can fail without any warning signs, so it’s always best to be prepared if you’re going to be working on your mower’s engine.

This is especially true if you’ve just refueled it and noticed symptoms.

Is a Fuel Pump the Same Thing as a Carburetor?

No. A fuel pump is used to get gas from your tank into your mower’s engine, where it is then mixed with air in the carburetor.

It should not be confused with the carburetor itself, which contains the fuel and air valves and other components to mix gas and air correctly.
Dull mower blade symptoms

How Do I Know If My Lawn Mower’s Fuel Pump Needs to Be Replaced?

It might need to be replaced if you’re experiencing any of the above symptoms, as well as other issues such as severe stuttering or trouble starting.

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It can be challenging to pinpoint precisely what’s causing trouble with your mower.

While it’s possible to test the fuel pump yourself, it might be a better idea to take your mower in for repair.

Not only will you save time and hassle, but you may also prevent further damage to your machine.


  • Ricky

    Hi, I’m Ricky. I’ve been involved in lawn care and landscaping from when I was 15. To be honest, I didn’t like the idea of pushing mowers, collecting grass clippings, and maintaining flowerbeds at the time. But having seem the passion my parents had for gardening and outdoors and the effort they put in maintaining the health and beauty of our landscape, I couldn’t help but not only admire their hard work but also I became a part of it. As someone who loves to spend time with nature’s best, I find myself learning a lot more about gardening and outdoors on a daily basis. Not to mention I love to share the knowledge I’ve gathered over the years with my readers at We Mow Dallas. To be clear, I don’t have a Master’s degree in gardening or anything like that. Everything I’ve learned about gardening, landscaping, and lawn care spring from passion and engagement with my parents. And with a ton of free information out there, plus the ability to run tests and determine what works best for lawn care and landscaping, every day is an opportunity to learn and implement something new. My goal with We Mow Dallas is to teach you exactly how to maintain your lawn and landscape. And since I walk the talk in reality, you shouldn’t hesitate to join me in this wonderful world of landscaping and lawn care. K Beatrice

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