How A Fuel Pump Works On A Lawn Mower: Explained

The lawn mower is one of the most commonly used outdoor equipment, and a fuel pump is an essential part of it. The fuel pump is responsible for delivering the right amount of fuel to the engine to run smoothly and efficiently.

In this article, we will discuss how a fuel pump works on a lawn mower and explain the various components that make up the pump.

How Does A Fuel Pump Work On A Lawn Mower?

The fuel pump on a lawn mower is a small but vital component that ensures the engine continues to run properly. It is responsible for pushing the gasoline from the fuel tank to the carburetor, which mixes it with air and turns it into a combustible vapor. With the proper functioning of the fuel pump, the lawn mower can run. Understanding how the fuel pump works on a lawn mower is important to ensure it continues operating at its optimum level.

The fuel pump on a lawn mower is typically located near the fuel tank. It is usually made of metal or plastic and has two main components: a diaphragm and a valve. The diaphragm is a flexible membrane that is connected to the valve.

When the engine is running, the diaphragm is continuously vibrating, and this causes the valve to open and close. As the valve opens, the pressure inside the fuel tank increases, forcing the fuel out. The fuel is then directed toward the carburetor and is mixed with air to create the combustible vapor.

In addition to the diaphragm and valve, the fuel pump on a lawn mower also contains a filter. This filter prevents dirt and other debris from entering the fuel system and clogging the fuel pump. The filter also helps to maintain the proper fuel pressure within the system. If the filter becomes clogged or damaged, it can cause the fuel pump to fail.

To ensure that the fuel pump on a lawn mower continues to function properly, it is important to perform regular maintenance. This includes checking the diaphragm and valve for wear and inspecting the filter for dirt and other debris. If any of these components are damaged or worn, they should be replaced. It is also important to keep the fuel tank full, as this helps the fuel pump to operate at its peak performance.

Types Of Fuel Pumps

Types Of Fuel Pumps

There are two main types of fuel pumps used on lawn mowers: mechanical and electric fuel pumps.

Mechanical fuel pumps are the most common type driven by the engine’s camshaft. They are usually located near the carburetor and consist of a diaphragm, a spring, and a valve. As the engine’s camshaft rotates, the diaphragm is forced up and down, creating a vacuum that sucks fuel from the fuel tank and pushes it through the fuel line into the carburetor.

An electric fuel pump is also driven by the engine and is located near the fuel tank. It uses an electric current to create a vacuum, which sucks fuel from the tank and pushes it through the fuel line. The electric fuel pump is more reliable and efficient than the mechanical fuel pump but is also more expensive.

How To Test A Fuel Pump?

To test a fuel pump, you can follow these steps:

  • Check for fuel pressure: One of the first things you can do is use a fuel pressure gauge to check the fuel system’s pressure. This will help determine if the fuel pump is functioning properly. Consult your vehicle’s manual for the specific fuel pressure requirements.
  • Listen for a humming noise: When you turn the key to the ON position (but not start the engine), you should be able to hear the fuel pump turn on. It should make a humming noise for a few seconds. It could be a sign of a faulty fuel pump if you don’t hear anything.
  • Test for power at the fuel pump: Using a multimeter, you can check for power at the fuel pump. Disconnect the electrical connector to the pump and connect the multimeter to the terminals. If there is no power, it could indicate a problem with the fuel pump relay or wiring.
  • Check for fuel flow: Another way to test the fuel pump is by checking if there is fuel flow. You can do this by disconnecting the fuel line from the fuel pump and attaching a hose to direct the fuel into a container. Then, turn the key ON and see if fuel is pumped through the line.
  • Consult a professional: If you’re unsure or uncomfortable with testing the fuel pump, it is always best to consult a professional mechanic. They have the expertise and tools to diagnose and fix any issues with your fuel pump accurately.

Lawn Mower Fuel Pump Troubleshooting

Here are some troubleshooting steps you can take if you’re having issues with your lawn mower fuel pump:

  • Check the fuel lines: Make sure the fuel lines are not kinked, clogged, or cracked. If they are, replace them and see if that resolves the issue.
  • Clean the fuel filter: A dirty or clogged fuel filter can prevent fuel from reaching the pump. Remove the filter and inspect it for any debris. If it’s dirty, clean or replace it.
  • Check the fuel pump fuse: Locate the fuel pump fuse in your lawn mower’s fuse box and inspect it for any signs of damage or a blown fuse. If it’s blown, replace it with a new one.
  • Test the fuel pump relay: Use a multimeter to test the fuel pump relay. If it’s faulty, replace it with a new one.
  • Inspect the fuel pump: If all else fails, you may need to inspect the fuel pump itself. Check for any signs of damage or wear. If it’s not functioning properly, replace it with a new one.

If you’re still experiencing issues after trying these troubleshooting steps, consult a professional or take your lawn mower to a repair shop for further diagnosis and repair.

Signs Of A Faulty Fuel Pump

Signs Of A Faulty Fuel Pump

Signs of a faulty fuel pump can vary, but here are some common indicators to look out for:

  • Difficulty starting the engine: A faulty fuel pump may struggle to deliver sufficient fuel, making it difficult to start or causing the engine to stall shortly after starting.
  • Engine sputtering or stalling: A failing fuel pump may lead to inconsistent fuel pressure, causing the engine to sputter or stall while driving.
  • Decreased fuel efficiency: If you notice a sudden decrease in your vehicle’s fuel efficiency, it could be a sign of a faulty fuel pump not delivering the proper fuel to the engine.
  • Whining noise from the fuel tank: A worn or defective fuel pump may produce a whining noise, especially when the engine runs at a low fuel level.
  • Loss of power during acceleration: An inadequate fuel supply due to a faulty fuel pump can result in a loss of power and poor acceleration performance.
  • Fuel odor: A faulty fuel pump can cause fuel leaks, which may result in a noticeable fuel odor around the vehicle.

If you experience any of these signs, having your vehicle inspected by a professional mechanic to diagnose and resolve any fuel pump issues is best.

Installing A New Fuel Pump

Installing a new fuel pump on your lawn mower is not difficult, but it is important to understand how a fuel pump works to ensure that you are installing it correctly. The fuel pump is responsible for delivering fuel to the engine, and it is typically mounted onto the side of the lawn mower’s engine.

The pump has an inlet line leading to the fuel tank and an outlet line leading to the carburetor. The fuel pump creates a vacuum in the inlet line, which pulls the fuel from the tank and pushes it toward the carburetor. This is how the fuel is delivered to the engine to be burned, creating the power necessary to make the lawn mower move.

When installing a new fuel pump, it is important to ensure that the inlet and outlet lines are connected correctly and that the pump is securely mounted to the engine. The inlet line should be connected to the fuel tank, with the outlet line leading to the carburetor. It is also important to ensure the fuel pump is mounted in the correct position, as an improperly mounted fuel pump can lead to performance issues.

Another important step when installing a new fuel pump is to ensure that the fuel pump is properly primed. This is done by filling the inlet line with fuel prior to connecting it to the fuel tank. This helps to ensure that the pump is filled with the correct amount of fuel, allowing the pump to start working properly. After the fuel pump is properly connected and primed, you can start the engine and test it to ensure it is working correctly.

Fuel Pump Maintenance

Fuel pump maintenance is an important aspect of keeping your vehicle running smoothly. Here are a few tips to help you maintain your fuel pump:

  • Regularly inspect for leaks: Check for any signs of fuel leaking around the fuel pump, which can indicate a problem. If you notice any leaks, it is important to address them immediately to prevent further damage.
  • Keep your fuel tank filled: Running your vehicle on a near-empty tank can cause the fuel pump to overheat. Make sure to keep your fuel tank at least half full to prevent this from happening.
  • Use high-quality fuel: Low-quality or contaminated fuel can damage the pump. Always fill up with reputable fuel from trusted sources to ensure the longevity of your pump.
  • Avoid running on empty: Running out of fuel can also cause damage to the fuel pump. It is best to avoid running your vehicle on an empty tank as much as possible.
  • Replace fuel filters regularly: Fuel filters help to prevent debris and impurities from reaching the fuel pump. It is important to regularly replace these filters to ensure proper fuel flow and prevent damage to the pump.
  • Follow the manufacturer’s recommendations: Different vehicles may have different fuel pump maintenance requirements. It is always best to consult your vehicle’s owner’s manual or follow the manufacturer’s recommendations for proper maintenance.

Fuel Pump Replacement Cost

Fuel Pump Replacement Cost

Replacing a fuel pump on a lawn mower can be a costly and time-consuming task. Depending on the make and model of the mower, a typical fuel pump can cost anywhere from $30 to $80 and will require the removal of the fuel tank to access the pump. The labor costs of replacing a fuel pump can also increase quickly if a professional technician does the job. On average, the labor cost for fuel pump replacement can be anywhere from $150 to $200, depending on the job’s complexity.

In general, fuel pumps deliver the fuel from the tank to the carburetor. On a lawn mower, the fuel pump will typically be located on the side of the fuel tank, though the exact location can vary depending on the make and model. The pump is typically a mechanical unit driven by the engine via a belt or chain, and it will usually be attached to the fuel tank by two or more screws.

Once the fuel pump has been located, it can then be removed. This will usually require disconnecting the fuel line from the pump and disconnecting the wiring and any other components that may be connected to the pump. Once the pump has been removed, it must be replaced with a new one. This process can involve replacing the old pump with a new one or rebuilding the old pump and replacing any parts that may have worn out.

Once the new pump has been installed, the fuel tank must be reattached. This process will involve reconnecting the fuel line and any other disconnected components during removal. The fuel tank must also be securely attached to the engine, as a loose fuel tank can be extremely dangerous.

Benefits Of A Fuel Pump

There are several benefits of having a fuel pump in your vehicle:

  • Reliable fuel delivery: A fuel pump ensures a consistent and reliable fuel supply to the engine. It helps maintain optimal fuel pressure, ensuring the engine runs smoothly and efficiently.
  • Improved engine performance: A properly functioning fuel pump ensures that the engine receives the right amount of fuel at all times. This helps improve the overall performance and responsiveness of the engine, resulting in better acceleration and power.
  • Fuel efficiency: A fuel pump in good condition can help improve fuel efficiency. Delivering the correct amount of fuel to the engine avoids wastage and ensures that fuel is used efficiently.
  • Longevity of the engine: A fuel pump is crucial in preventing engine damage and wear. Delivering a consistent flow of fuel prevents the engine from running too lean or too rich, which can lead to problems like overheating or premature engine wear.
  • Convenience: A fuel pump in your vehicle eliminates the need to pump fuel from the tank manually. This makes refueling more convenient and allows for a more seamless driving experience.

How To Properly Fuel Your Lawn Mower?

Knowing how to fuel your lawn mower properly is important if you want it to run efficiently and last a long time. To properly fuel your lawn mower, follow these steps:

  1. Use the right fuel: Most lawn mowers require unleaded gasoline with an octane rating of 87 or higher. Avoid using gasoline with an ethanol content higher than 10%, as it can damage your mower’s engine.
  2. Check the oil: Before fueling, check the oil level in your mower’s engine and add oil if necessary. Refer to your mower’s manual for the required type and amount of oil.
  3. Choose a well-ventilated area: Fuel your lawn mower in a well-ventilated outdoor area to prevent the buildup of dangerous fumes. Avoid fueling near open flames, sparks, or any potential ignition sources.
  4. Turn off the engine: Always turn off the mower’s engine before refueling to prevent accidents or fuel spillage.
  5. Remove the gas cap: Open the gas cap slowly and carefully to release any pressure buildup. This will prevent fuel from spraying out or causing injury.
  6. Refuel carefully: Slowly pour the fuel into the fuel tank using a funnel or a nozzle to prevent spills. Avoid overfilling the tank, as this can lead to fuel leakage.
  7. Replace the gas cap: Make sure the gas cap is secured tightly to avoid any fuel leaks during operation.
  8. Wipe-up spills: If you spill any fuel during refueling, wipe it up immediately to prevent accidents or damage to the mower.

How To Properly Store Lawn Mower Fuel?

Storing lawn mower fuel properly ensures that your mower runs smoothly and efficiently. Here are some tips on how to store lawn mower fuel properly:

  1. Use a fuel container specifically designed for storing gasoline. These containers are typically made of durable materials resistant to leaks and spills.
  2. Fill the fuel container only about 95% full to allow for expansion. Gasoline expands when it gets warm, so leaving some room at the top of the container will help prevent spills and leaks.
  3. Store the fuel container in a cool, dry, and well-ventilated area. Avoid storing it near any sources of heat or ignition, such as a water heater or furnace.
  4. Keep the fuel container away from direct sunlight, as exposure to sunlight can accelerate the breakdown of gasoline.
  5. Add a fuel stabilizer to the gasoline before storing it. This will help slow down the oxidation and degradation of the fuel, keeping it fresh for a longer period.
  6. Label the fuel container with the purchase date or the filled date. This will help you track how long the fuel has been stored and when it should be replaced.
  7. Avoid storing gasoline for long periods. Gasoline typically degrade after about 30 days, so it’s best to use it up within that time frame if possible.


In conclusion, understanding how a fuel pump works on a lawn mower is important to ensure the efficiency and longevity of the machine. A fuel pump helps to keep the lawn mower running by delivering fuel from the tank to the engine.

It is vital to any properly functioning lawn mower and must be inspected, maintained, and replaced. With regular maintenance and the right knowledge, a lawn mower’s fuel pump can ensure the machine stays running smoothly.

Frequently Asked Questions:

What type of fuel should I use in my lawn mower?

Most lawn mowers run on either unleaded gasoline or diesel fuel. However, checking the owner’s manual to confirm the fuel type recommended for your lawn mower is important.

How often do I need to replace the fuel pump in my lawn mower?

The frequency of fuel pump replacement for a lawn mower will vary depending on the make and model. Generally, fuel pumps should be replaced every two to three years or after 200-300 hours of use. It is always best to consult the manufacturer’s manual for specific maintenance information.

Is it safe to repair a lawn mower fuel pump myself?

No, repairing a lawn mower fuel pump yourself is unsafe. Fuel pumps contain flammable gas and require specialized tools and knowledge to repair. Taking your lawn mower to a professional mechanic experienced in fuel pump repairs is best.

How do I know if my lawn mower fuel pump is malfunctioning?

If your lawn mower fuel pump is malfunctioning, you may notice that it is not starting, running rough, or not running at all. Other signs may include fuel leaking from the fuel line or a lack of fuel pressure. If you suspect that your fuel pump may malfunction, it is best to take it to a qualified mechanic to check and repair it.