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John Deere Lawn Mower Won’t Stay Running: Troubleshoot Guide


John Deere mower starts but dies.

It’s Saturday morning, birds are chirping, and you have decided to finally get your lawn in shape. But there’s a problem: your reliable John Deere lawnmower is starting and then stalling every few minutes. Grrr!

If your John Deere lawn mower won’t stay running, there are several potential causes:

  • Stale or old gas
  • Carburetor issues
  • Gas line and filter
  • Dirty spark plug
  • Dirty air filter

Thanks to the sturdy yet straightforward engine your lawnmower runs on, you can fix most of these issues with only a few tools and little DIY knowledge. Read on to learn how to recognize each issue and solve it quickly and painlessly!

This is the exact troubleshooting process I went through recently with my John Deere mower when it wouldn’t stay running. I know it is frustrating but we can troubleshoot this! Let’s get to work.

Note: if your mower won’t even start, watch this short troubleshooting video from Jeff’s Little Engine Service. But if it’s starting but won’t stay running, keep reading.

Stale Or Old Gas Issues

Whether your lawnmower runs on a two or four-stroke engine, old, obsolete, or oxidized gas can result in a loss of power. If not resolved promptly, this issue can eventually lead to engine failure. Here is what can cause gas issues and how to solve them depending on the kind of engine your lawnmower boasts:

2-Stroke Engines

John Deere makes some 2-stroke push mowers. If this is your equipment, let’s make sure you understand the difference. These engines do not possess an oil injection system, so they run on a premix of gas and oil, which is inserted directly in the engine.

Note: These push mowers usually use a Briggs & Stratton engine although sold under the John Deere brand.

If the gasoline used for the mix is old, it could have attracted water, which, in turn, can oxidize the fuel. Always use a gas that has 10% or less ethanol. I prefer to use ethanol-free gas which stores longer.

Read Does Ethanol-Free Gas Go Bad? Fuel Shelf Life Comparisons.

If you notice your lawnmower overheating and the suddenly losing power, one of the possible causes is that the premix has gone bad. Since this prevents the engine from working correctly, empty the gas tank, fuel line, and proceed to flush the old gas out. Try again with a newly blended premix.

4-Stroke Engines

John Deere’s riding mowers usually have a four-stroke engine. The oil enters separately. As long as there is enough oil in reserve, the issue almost always lies in the gasoline.

If you have used ethanol-based gas in your lawnmower that was sitting in your garden closet for over six months, it might have absorbed water. Ethanol can cause significant issues to a mower including malfunctioning in the engine and, if you left the old gas in the machine, even ruined the parts of the engine.

Carburetor Issues

Due to the bustling activity that takes place in it, this component is also the most likely to show signs of damage. Luckily, carburetors are also among the most accessible parts to repair and replace, if needed.

Carburetors have the crucial task of creating the perfect mix between fuel and air. Such elements, when sparked, give life to combustion, the process that is at the core of your lawnmower.

The most common issues with a carburetor are impurities and cracks in the integrity of the casing.

Impurities

If your lawnmower starts and stays in idling but then stops abruptly as soon as you increase the throttle, the carburetor might be dirty or clogged. In this case, you will need to clean the carburetor throughout with appropriate carb cleaning spray.

  1. Start by draining the carburetor. 
  2. Then proceed toward taking apart the filter, fuel line, and spark plug. 
  3. After spraying it with the cleaning product, you may reassemble the components and let the spray do the job while your lawnmower is working.

If you are a little lost, watch this short how-to guide from YouTube. Sometimes seeing someone go through the process makes it a little easier to follow.

Cracked Carburetor

This is less common but if, while cleaning the carburetor, you notice cracks and ruptures, the only thing to do is swap it for a new one. Carburetors are particularly inexpensive and easy to find in your closest John Deere service center or online.

Amazon sells aftermarket carburetors that are compatible with John Deere (link to Amazon) – just check your mower’s model number to make sure you get the right one.

And by the way, another sign that the carburetor might have cracks is leakage from the lawnmower while working. If you notice this, stop the engine immediately.

Carburetor Adjustment 

You may need to adjust the carburetor to regulate the amount of air and fuel entering the engine. Often, carburetors have two levers, “high” and “low.”

Here’s a helpful video on adjusting the carbs:

Gas Line And Filter Issues

Gasoline produces residues that, over time, can stagnate at the bottom of the gas tank. However, these residues are filtered by the fuel filter, which prevents them from entering the engine. It is very common for the filter to become dirty and clogged, which prevents enough fuel from reaching the engine. 

A symptom of this issue is your lawnmower working correctly on idle and then dying as soon as you increase the power. This is because the clogged filter can allow some gas through but not enough when the demand is increased.

A clogged fuel filter can prevent the mower from starting or cause it to die when increasing power from an idle.

Ethanol can play a role in this too. The ethanol in gasoline can break down the sediments in the tank, which are now small enough to pass through the filter. In this case, they might end up in the carburetor or in the engine itself.

Dirty Spark Plug

Now that you have made sure that the carburetor is supplying enough air and the fuel filter allows enough gas through the line, the next thing to check is the spark plug.

A dirty spark plug will cause your lawnmower to stop suddenly after a few minutes of work as there is no spark happening in the engine and, therefore, no combustion.

Most manufacturers recommend changing the spark plug once a year. I wish I could say that I do that, but I don’t. Honestly, I don’t change it until it stops getting fire.

The point though is that you may need to change it and it’s a super-simple thing to do. This YouTube video walks through the process step-by-step if you need some guidance.

Dirty Air Filter

Similarly to what happens because of a dirty fuel filter, if the air filter is unclean, your lawnmower will suddenly die as soon as you increase the throttle.

The engine needs air to start the combustion process, which enters the machine through this filter. However, no dust or other outside damaging particles must be allowed in the engine. The air filter is responsible for delivering only fresh, clean air.

But in the process of filtering all of that air, they can get clogged up pretty easily. The filter will build up with captured dust and particles and won’t be able to deliver enough air to the engine, which will choke when on a higher throttle.

The air filter in a lawnmower can become clogged with dust and debris, preventing the engine from getting enough air to run effectively.

To solve any issue related to the air filter, you have two options: clean it or replace it. They are pretty inexpensive so I tend to just replace them but if you want to clean it, here is the process:

  1. Remove the housing that covers the air filter. My mower has two hand screws that hold it secure.
  2. Pull the filter out and wash it thoroughly with dish soap and lukewarm water.
  3. Once you have removed all the debris that was blocking the passage of air, ensure that the filter is entirely dry before mounting it back on.

Manufacturers suggest cleaning the filter once a year for better maintenance. Considering how much dust you can kick up during the year while mowing, this is probably a solid guideline.

Conclusion

While a John Deere lawnmower is one of the sturdiest pieces of outdoor equipment you could invest in, it still needs a little attention now and then. If the mower starts but won’t stay running, you can probably trace the issue to one of the areas I’ve outlined.

Check for a faulty spark plug, carburetor, air filter or fuel line. Each of these issues has a simple solution that you can try out before calling in the pros.

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Paul Brown

Paul has a two-acre yard on red clay soil in Southeast Texas. He knows exactly what the challenges are to nurturing a thriving yard in difficult soil. He takes a practical approach to yard improvement and enjoys putting best practices and “golden rules of lawn care” to the test. Click here for Paul’s author page

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