Constant stopping and starting is annoying when you are doing any household task. But it’s super irritating when you are lawn mowing.

On a nice sunny day the last thing you want is a rough time or a start then immediate stop with your lawn mower.

Want to avoid this frustration in the future? You’ve come to the right place! Have a read on to learn all about lawn mower fuel pumps and a ‘how to’ on testing or swapping them.

Does a lawn mower have a fuel pump?

Almost every lawn mower will have a fuel pump. Whether the lawn mower you are using is gas or electric, the fuel pump allows the machine to run by converting fuel to power via the carburetor. By shifting the power through the machine, the fuel pump acts as an important link in lawn mowers and makes sure that your mower keeps going and doesn’t cut out. Because of the role they play in the make-up of your mower’s engine, fuel pumps are pivotal and without one you can face constant stoppages or backfiring before your lawn mower will plainly just stop running.

This article will look at what a fuel pump is and how they work in relation to your machine. It will then cover how to know if your pump is bad and how to replace it accordingly. We will then compare common problems across different brands of mower before having a look at the increasingly popular electric mowers and how fuel pumps fit in with them. We aim to tell you everything you need to know about your lawn mower fuel pump, so you can keep on mowing with ease!

Push mowers

You will find that it is most likely your push mower will have a fuel pump installed in it. It will be found mounted in between the engine’s carburetor and the fuel tank and acts as an important link between the two. It can be found without too much trouble upon lifting the lid of the outer casing. It is easily identifiable and tends to be round with lines coming in and out of it. Because of their important nature, it is important that nothing obstructs the fuel pump. This does become problematic as without close and constant maintenance these pumps do tend to face issues such as clogging or damage.

Riding mowers

In much the same vein as push mowers, riding mowers also have fuel pumps. They act in exactly the same manner in riding mowers (they are actually used on all types of motor vehicle). In riding mowers, they tend to need more power and can themselves be powered electrically. This means when dealing with any repairs or maintenance you want to take extra precaution to avoid frazzling yourself. Just like push mowers these fuel pumps are found linking the fuel tank and the carburetor and are usually round with pipes attached. In riding mowers they are found under the seat and are usually really accessible. This makes for easy access for maintenance and repairs.

How do fuel pumps work on lawn mowers?

Fuel pumps provide a vital function in lawn mowers. Simply they link the fuel tank to the engine and make sure the motor keeps running to avoid stoppages to grass cutting. They are usually used when the fuel tank is built lower than the engine and act as a pump to send enough constant fuel to the engine to allow the machine to run.

How do I know if the fuel pump on my lawn mower is bad?

The main way you can identify that your fuel pump isn’t functioning how it should be is plain and simply if the engine doesn’t work or starts to cut out on you. When the fuel pump is broken it will lead to the engine not receiving enough fuel and so the mower will fail to run. Perhaps the most obvious case of this happening is when you turn the ignition key or pull the string and the mower doesn’t turn on. But even after starting up your pump you can still face issues showing it is broken, most obviously going up and down hills cutting out your mower or cutting through tall thick grass because it is simply not receiving enough fuel from the tank. The good news is, this problem has an easy fix meaning it’s not going to cost you much or take you too long to repair.

Also read: How Long Does A Lawn Mower Spark Plug Last

How to test a lawn mower fuel pump?

Importantly, move your mower to a flat surface. In order to test your fuel pump you need to know where it is. So, first things first, locate the pump. This is easily done following opening up the casing of your mower and following the line/pipe from the fuel tank to the black connector further down the line, which will have other pipes coming out of it at different angles as well. To test your pump you will want to disconnect the fuel pump pipe from the side that connects to the carburetor (check out the link for another guide).

Which can either be done using a wrench or a hose clamp depending on your model of mower. You will need a set of pliers/clamp to use here to curb the fuel from flowing out whilst doing this. Making sure the fuel tank has fuel in it, you should then aim the pipe into a pan or container. You then want to turn the engine on and you should see how much fuel is running through the fuel pump. If it is a nice flow your pump should be working fine, if it is a mere trickle then you need to be looking at replacing your fuel pump!

How to prime a lawn mower fuel pump

By priming your mower, you avoid the cranking and needless pressure on your engine that would be present without the adequate oil pressure. Priming your lawn mower is a useful old school skill to have and many will already know their way about priming. Infact, if the fuel pump is working well it should be able to prime itself by running the primer through it. However if it has faced some damages you may need to manually prime your mechanical pump. To prime you want to find the same hose/pipe you disconnect to test your fuel pump.

Once disconnected you want to stick a rag over the end of the pipe. After this you will need to spray a 3 second burst into the carburetor then pull or turn the ignition. It should last about 3-5 seconds before cutting out – you can check the rag to see if this is working. If you repeat this process for a few times, you will eventually prime the engine for it to start easily. Be warned of backfire with some engines which can be problematic around oily rags and fuel pipes.

What causes a fuel pump not to prime?

Following extended periods of disuse, an engine may need to be primed before it is started up again. This is common in lawn mowers coming out of their winter hibernation. Despite normally being able to prime themselves after sticking in some oil some lawn mowers will not prime. This can also happen when you manually try to prime the machine. The reason for this is more often than not a dodgy fuel filter which is damaged or clogged. When the fuel filter isn’t functioning as it should be, the pressure for the injectors is not high enough and the fuel pump can’t work effectively.

How to clean a lawn mower fuel pump

Whether it be a clog from fuel left over in the tank over winter or else just an unfortunate clogging of the fuel pump through general wear and tear, you will probably face issues with your fuel pump. The best way to clean a fuel pump is simply to use fuel system cleaner. Firstly you want to turn the fuel valve to the ‘OFF’ position so as to avoid any dangerous issues. You then want to check with a flashlight to see if there are any blockages, cracks or debris. If you notice any structural damage to your lawn mower you are best to have an expert have a look at it cause it can lead to serious damage.

Once you have finished all these checks you can then freely whack the fuel system cleaner along with the correct ratio of fuel into your tank, which should run through the pipes and give them a lovely clean allowing for a much more smooth and easy ride next time out. Remember, always check the manual of your specific motor just to make sure it doesn’t have any obscure irregularities, and also it would be useful to implement regular maintenance of your lawn mower to make sure it will always function correctly.

Also read: What Kind of Gas to Use for your Lawnmower

Common Fuel pump problems

Fuel pump problems can be hard to diagnose sometimes. This means without adequate mechanic knowledge you may struggle to identify all the issues. However, there are a number of obvious fuel pump failing indicators. Noisy fuel pumps, engines that are slow or do not start and mowers that lack power for distance, cutting or landscape are all obvious indicators you could be facing a fuel pump issue.

John Deere lawn mowers

Despite being rightfully well known for their sturdy nature, these solid machines do tend to have a common small fuel pump issue. John Deere famously uses Kawasaki motors on their mowers. Users of Deeres have commonly reported that following 30mins of use, the mowers sometimes shut off completely for 5-10mins. Now this could be due to a number of issues, but it has been commonly found that these issues are related to vent holes in the fuel cap are plugged or alternatively, there is a hole in the pipe somewhere between the fuel tank and pump which is leaking all the fuel lowering the level of the fuel pump much quicker than normally. Once identified these can be easily repaired within a couple of hours but its the issue of sussing out the problem which could take time.

Husqvarna

The biggest issue people face with Husqvarna lawn mower fuel pump problems is related to the gas that is being fed into the tank. If you don’t use premium gas, you are likely to face an issue with regards to the fuel pump and its efficiency alongside the engine of your mower. People also tend to face issues with their fuel pumps when the Husqvarna engine has had direct impact with the wet. Many people are claiming that they are particularly susceptible to water damage. It’s a case of using premium gas and only mowing when it’s very dry, which could be a tad restricting.

Craftsman

In Craftsman mowers the fuel pump has 3 ports. (the gas in port, the gas out port and the pulse port). If the engine oil is overfilled the oil can enter the pulse port line and damage it, preventing it from functioning properly. Alternatively, Craftsmen usually have small check valves on the gas ports, which normally prevent gas from reentering the fuel tank. These can easily fail and cause issues. You want to make sure these are all checked on a Craftsman mower as they are common issues regarding fuel pumps in this design. If there are any issues surrounding your fuel pump, it is advised that you completely replace it for a new one. It’s a case of regular maintenance with Craftsman mowers, because if you do face a problem you are usually looking at a complete overhaul.

Kawasaki

Known for their longevity and being a great solid piece of machinery these motors are fantastic pieces of kit but do have their faults. The most common problem you may face with a kawasaki fuel pump is in the diaphragm which is used within the mechanical pump. The diaphragm through damage or else just general use may puncture leading to the need for a replacement. Luckily due to the nature of these machines, if someone who knows what they are doing is repairing it, it can be done in as little as 15 minutes.

Converting to Electric fuel pump for lawn mower

Newer lawn mowers will probably already have an electrical pump built in as they have been widely regarded as superior to mechanical pumps in recent years. They can provide a much more precise, high-pressure flow rate which allows for optimum power in your mower whilst also being nice and friendly for the environment.

Is it possible?

If you have an older mower you may be battling with a mechanical pump and all the woes that are attached to it. But, in a few easy steps you can easily install a brand new electric pump to replace your mechanical pump. When replacing it you have two choices. You can install the electrical pump alongside the existing mechanical pump for them both to use. But this seems needless when the design of electrical pumps is meant for a long time. Instead, the better option would be to replace the mechanical pump completely. This requires you to dismantle the whole existing fuel pump system, including the lines and install a whole need electric connecting fuel pump system between the fuel tank and engine.

Benefits

This new electric pump will be more long-lasting, tend to suffer less problems than mechanical pumps and are more efficient both environmentally and economically. Electric pumps are more accurate and adjustable and can provide a more precise flow of oil and fuel into the engine to allow it to function much better.

How to do it

In much the same way you use to service or repair your fuel pump, installing an electric fuel pump first requires you to stop the flow of fuel from both engine and fuel tank end through clamps. You then want to uninstall the mechanical pump via screws, normally. It’s then a case of a simple, straight swap where the electric pump is subbed in. Connect it to the existing lines but install a new fuel filter. Then you need to wire the electric pump to the ignition and you should be sweet to go. If you know what you are doing it can be done easily. If not, here is a good video to help you.

What to be aware of

Despite the reliability of the electric fuel pumps, which now dominate the market, there are a few things that can and do go wrong. The problems tend to occur when they are installed poorly. Electric pumps push fuel instead of pulling it, so you want to install the pump close enough to the gas tank to allow optimum pressure. Additionally, the positioning of your electric pump is important. The electric pumps don’t mix well with heat sources such as exhausts, and also to keep them out of really enclosed areas. Both of which can lead to fires and a struggle of a fight against insurance companies. The final point of concern when installing electric fuel pumps which is worthy to include is to have a fail safe in place which automatically shuts off the electric pump if something goes wrong. For this it would be sensible to consider installing an oil pressure switch or something similar.

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