How To Replace Fuel Pump on a Lawn Mower (12 Easy Steps)

If there is something wrong with your lawn mower’s fuel pump, then you’ll have to replace it. Thankfully, installing a new impulse fuel pump on your lawn mower is a quick and easy process. So, to get your lawn mower firing how it usually does, let’s go over how to replace a fuel pump on a lawn mower.

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How to Replace a Lawn Mower Fuel Pump (The Overview)

To replace a lawn mower fuel pump, you first need to remove the three connected lines: the fuel line from the fuel tank, the fuel line going to the carburetor, and the line coming from the OHV. Once these lines are disconnected, you can remove the old fuel pump. Finally, install the new pump and reconnect the three lines.

Symptoms of a Bad Fuel Pump on a Lawn Mower

One of the most common issues with a bad lawn mower fuel pump is a failing diaphragm. This is the small rubber internal diaphragm that pulls and pushes fuel from the fuel tank to the carburetor. The continuous movement and exposure to gasoline during operation and storage can cause the diaphragm to fail. As a result, you will notice several symptoms that, over time, become progressively worse until the lawn mower fuel pump completely fails. Here are some of the symptoms of a bad fuel pump to look out for.

Difficulty Starting Your Lawn Mower’s Engine
Lawn Mower Engine Stalls
Engine Sputtering
Loss of Engine Power
Engine Surging
Engine Struggles with High RPM

How Do I Know if My Fuel Pump is Broken

To confirm that your lawn mower fuel pump is bad, you’ll need to carry out several tests. These tests are designed to eliminate other components within the fuel system that present similar symptoms as a bad fuel pump. So, you might need to clean clogged lawn mower fuel lines or replace your mower fuel lines instead. But if your lawn mower fails the tests, then your lawn mower fuel pump will need to be replaced.

Here are the tests for how to test a lawn mower fuel pump.

Test the Fuel Flow from the Fuel Tank to the Fuel Filter
Test the Fuel Flow from the Fuel Tank to the Fuel Pump
Test the Pressure from the OHV
Test the Fuel Flow from the Fuel Tank to the Fuel Pump Outlet
Test the Fuel Flow from the Fuel Tank to the Carburetor

If you’re still in the stage of determining whether your fuel pump is the cause of your lawn mower problems, then read my article on how to test a lawn mower fuel pump for a thorough guide on each of the tests.

Can a Bad Fuel Pump Be Fixed?

Typically, a lawn mower fuel pump is a sealed unit, meaning you can’t repair it. So, you’ll more than likely need to replace it with a new unit. Thankfully, lawn mower fuel pumps are not expensive components. Fuel pumps for lawn mower engines such as Briggs & Stratton can cost as low as $15 to replace if you choose to install the pump yourself.

How To Replace Fuel Pump on a Lawn Mower (Step-by-Step)

If your lawn mower fuel pump is a non-electric type, then it is likely to be an impulse fuel pump. This type of fuel pump operates with positive and negative pressure from the overhead valve (OHV). You can easily figure out if this is the type of fuel pump on your mower. First, take a look at the pump. You should see three lines connected to the fuel pump. If one of the lines connects to the valve cover located on the side of your lawn mower’s engine, then you have an impulse fuel pump. This fuel pump is the typical design for most large lawn mowers such as riding, tractor, zero-turn, and some large walk-behind lawn mowers.

So, let’s go over how to install a new lawn mower impulse fuel pump.

12 Steps to Install a Ride-on Lawn Mower Fuel Pump

Remove the spark plug cable from the spark plug.
Switch off the fuel cut-off valve or clamp the fuel line.
Remove the three clamps from the fuel pump inlet/outlet/OHV lines.
Remove the three lines connected to the fuel pump inlet/outlet/OHV.
Remove the fuel pump mounting bolt.
Lift the faulty fuel pump off of your lawn mower.
Position the new fuel pump.
Install the fuel pump mounting bolts
Connect the three fuel pump lines inlet/outlet/OHV.
Reposition the three fuel line clamps.
Turn the fuel back on by opening the cut-off valve or by removing the fuel line clamp.
Reconnect the spark plug.