How to Clean a Clogged Fuel Pump

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If your lawn mower is sputtering, stalling, or maybe not even starting at all, then you could have an issue with a clogged fuel pump. Now depending on your specific pump, you may be able to clean it. So before you head to the store for a new pump, let’s look at how to clean a clogged fuel pump. This process could save you a pocket full of money.

cleaning clogged fuel pump

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How to Clean a Lawn Mower Fuel Pump (Overview)

To clean a lawn mower fuel pump, you’ll need first to remove the fuel pump from your lawn mower. Next, you’ll need to disassemble the pump and inspect it. Once you have confirmed that the pump is in working condition, you’ll need to clean the pump thoroughly. Finally, reassemble and reinstall the pump.

Symptoms of a Clogged Fuel Pump

If you suspect your lawn mower fuel pump is clogged, you’ll want to look for any potential symptoms. Here is a list of telltale signs of a clogged fuel pump.

Types of Lawn Mower Fuel Pumps

There are two main types of fuel pumps used on riding mowers: electric and mechanical. Typically newer riding lawn mowers use mechanical pumps, whereas older models use electric pumps. Here’s a closer look at the two different types of lawn mower fuel pumps. This will help you determine which pump your lawn mower uses.

Lawn Mower Electric Fuel Pump

Electric lawn mower fuel pumps are simple inline pumps that suck fuel into the inlet and pump fuel out of the outlet. These types of pumps are powered by the lawn mower’s battery when the ignition is set to run and start. Usually, an electric fuel pump is located close to the engine or inside the fuel tank. An easy way to tell if your lawn mower uses an electric fuel pump is to check if the pump has any electric wires attached. 

Lawn Mower Mechanical Fuel Pump

Mechanical fuel pumps are commonly called vacuum pumps or pulse pumps. Now this fuel pump type is powered by air from the overhead valves (OHV). As the valves move in and out of the engine, a pulse of air is sent into the pump to push and pull the pump’s diaphragm. This pulsing action within the pump first pulls fuel through the fuel system, then pushes the fuel to the carburetor. To check for this type of pump on your mower, see if your fuel pump has three connections. Mechanical fuel pumps have one connection from the fuel tank, one connection to the carburetor, and a final connection to the OHV. 

Can You Clean a Lawn Mower Fuel Pump?

Well, this really depends on the specific fuel pump and its design. So, how do you tell if you can service a fuel pump? First, you’ll need to take a closer look at the fuel pump. Let’s go over what to look for.

Checking an Electric Fuel Pump

An old John Deere x485 has a small filter screen at the bottom of the pump that can be removed for cleaning. However, most modern inline electric fuel pumps simply have an inlet, outlet, and that’s about it. So, if your sealed modern electric pump doesn’t have a filter, you won’t be able to clean it. So if the pump is clogged, you’ll more than likely have to install a replacement pump. As a result, this design relies on the fuel filter always doing its job. This is one good reason to make sure you always replace your lawn mower fuel filter on time.

Checking a Mechanical Fuel Pump

When it comes to mechanical lawn mower fuel pumps, you have a 50/50 chance of having a serviceable pump. First, check the pump’s face plate and see if it is screwed on or sealed in place. If it is sealed without screws, unfortunately, you’ll have to install a new pump. But if you are one of the lucky ones with a removable face plate, you can take the pump apart and clean it. But, in my experience, these are few and far between, and getting replacement parts is nearly impossible. I’m pretty sure the manufacturer just wants you to throw away the old pump and buy a new one. Thankfully a new mechanical fuel pump only costs around $10-$20.

How to Unclog a Lawn Mower Fuel Pump (The Steps)

Because the most common type of modern lawn mower fuel pump is mechanical, I’ll go over how to unclog this type of pump. In this example, I’m using a Mikuni-style fuel pump found on many Briggs and Stratton engines. 

Removal

  1. Remove the spark plug ignition cable.
  2. Switch off the lawn mowers ignition.
  3. Switch the fuel cut-off valve to OFF.
  4. Locate the mechanical fuel pump.
  5. Slide the three spring clips attached to the fuel pump down each attached hose.
  6. Remove the three attached hoses from the fuel pump.
  7. Remove the fuel pump’s mounting screws.
  8. Remove the fuel pump from your lawn mower.

Disassembly

  1. Remove the screws from the face of the fuel pump.
  2. Remove the fuel pump face plate.
  3. Remove the face plate gasket.
  4. Remove the fuel pump diaphragm.
  5. Remove both check valves.
  6. Remove the rear gasket.
  7. Inspect all parts for wear.
  8. Replace any damaged parts.

Cleaning

  1. Spray each part of the fuel pump with a carburetor cleaner.
  2. Clean out each of the three pipe connections using a small pipe cleaner.
  3. Using a cloth, clean the faceplate, rear plate, and main body of the fuel pump.
  4. Lightly clean the gaskets and check the valves.

Assembly

  1. Install the check valves into the main body of the fuel pump.
  2. Place the rear gasket onto the rear face plate.
  3. Place the main body on top of the rear gasket.
  4. Place the diaphragm into the main fuel pump body.
  5. Place the face plate gasket onto the main body of the fuel pump/
  6. Place the face plate onto the face plate gasket.
  7. Install the face plate screws.

Installation

  1. Position the fuel pump onto the lawn mower 
  2. Install the fuel pump mounting screws.
  3. Connect the three hoses to the fuel pump.
  4. Reposition the three spring clips.
  5. Turn the fuel back on.
  6. Attach the spark plug ignition cable.
  7. Start the lawn mower.
  8. Check for leaks.

What You’ll Need to Clean a Lawn Mower Fuel Pump

How to Prevent a Fuel Pump from Clogging

Most of the time, fuel pumps become clogged by either using bad fuel or debris entering the fuel system. So, make sure that you are only using fresh new fuel and avoid using old fuel. Secondly, stay on top of regularly replacing your fuel filter. I recommend changing the fuel filter at least once a year or any time you notice the fuel filter is causing fuel flow issues.

Could The Problem Be Something Other Than the Fuel Pump?

The fuel pump is just one of many components responsible for getting fuel from the fuel tank and into the cylinder. Because all of the components create the same issues when faulty, this means that any one of the components can be at fault. 

So if you tested your lawn mower fuel pump and found that it’s working fine, I recommend you look at the following items.

Now if everything is ok with all of the components in the fuel system, then it is time to look elsewhere for problems. There are a few other parts of your lawn mower that could be causing the stalling, sputtering, and general poor performance. Here are a few examples of what else you could try.

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