Why Riding Lawn Mower Runs For 20 Minutes Then Dies? [Fixes]

A Riding Lawn Mower Runs For 20 Minutes Then Dies, usually has one of these three issues which is dirt in the fuel lining system, fault in the carburetor solenoid, or clogged carburetor. Also, there’s a 10% chance that you have a defective kill switch or Spark Plugs. 

To Fix it, you need to:

  • Clean the fuel cap and the fuel filter and change them if necessary.
  • Check the spark plug, carburetor solenoid, and the kill switch status.
  • If both are okay, you need to open up your engine and clean the inside of your carburetor manually.

Follow this post for a detailed walkthrough of each process and fix your lawn mower’s engine issue.

Key Takeaways

  • When your lawn mower runs for 20 to 30 minutes and then dies, the fuel cap, the fuel filter, or the carburetor choke usually has dirt.
  • Broken spark plugs and faulty kill switches may also cause this issue, but it’s uncommon.
  • If you want to clean the carburetor choke yourself, you should at least have an intermediate level of mechanical knowledge.

Troubleshooting Riding Lawn Mower Runs For 20 Minutes Then Dies problems

For any kind of engine, dirt is one of the greatest enemies. Additionally, they affect your riding mower more since it has closer contact with dirt and debris. 

Mainly, when there’s dirt in your Lawn Mower’s engine parts, it stops running after some time. However, cleaning those components can be a hassle if you don’t follow the proper process.

So here’s a simple process for cleaning each affected part thoroughly.

Reason 1. Fuel Cap Blockage

Every Lawn Mower Fuel cap has a tiny hole, which inserts Air into the Fuel tank as the engine burns the fuel. 

If there’s dirt on your fuel cap, it blocks the ventilation hole, creating a vapor lock. And when vapor lock happens in your mower, it won’t get enough fuel, so your engine stops after some time, in our case 20 minutes.

READ: Riding Lawn Mower Steering Problems – [4 Causes + What To Do?]

how to fix?

  • 1. Loosen The caps
Loosen The caps
Loosen The caps

As a quick fix, you can loosen the Fuel caps to insert additional air into your fuel tanks. You don’t have to take the fuel cap off; just go to the point where it’s slightly loose and wobbles. 

Those additional airs will help the gasoline flow into the carburetor, and your engine will run longer. But you shouldn’t use this fix permanently because it will mix additional smut in the fuel.

  • 2. Clan The Fuel Cap

Cleaning the fuel cap is the best solution for vapor lock. Though you can clean it using your hand, I recommend using an ultrasonic cleaner.  Here are the steps:

  • Detach the gas cap from the tank and take out the rubber insert.
Detach the gas cap
  • Put the cap and the rubber vent facing downwards in the tray.
Put the cap and the rubber vent
  • Put the cleaning tray in the ultrasonic cleaner and submerge the cap and piece of rubber.
Put the cleaning tray in the ultrasonic cleaner
  • Run the device for five or ten minutes, and it’s done.

But if you don’t have one, you can use your kitchen sink or a hot, soapy water bucket. Place the parts in it and let the fine debris inside the vent soften, then clean it with your hands.

Reason 2. Faulty Fuel Filter

There’s always some dirt and debris in the gasoline you use in your lawn mower– that’s why it has a fuel filter between the fuel lines. But in most cases, the factory fuel filter is shorter. So it easily becomes faulty after some time.

how to fix?

You should change the factory filter to a bigger Atlas Universal Lawn Mower Fuel Filter. Those filters have a screen inside and can filter out more dirt than these little red ones.

You will get them at $13.99 on their website.

Reason 3- Broken Spark Plugs

Though it’s very uncommon, sometimes a broken Spark Plug can make your riding lawn mower stop suddenly. When a Spark Plug goes bad, it can’t ignite the fuel when the engine asks, making the engine stop in the middle of the work.

how to fix?

You need to check the spark plug status using these steps:

  • Press and hold the ignition key and make the engine hot.
  • Pull out the spark plug and Plug the tester into the spark plug.
  • Insert the other lead into the spark plug boot.
  • Turn the engine over and check for the light to come on.

If you see light, then it’s ok. But if you don’t see any light, change the plug from any servicing center.

Reason 4. Defective Carburetor Solenoid

The solenoid in your carburetor works like a switch for an electrical impulse, causing a mechanical movement. It adjusts engine rpm when you turn on your engine. 

So when it becomes faulty, the engine loses the RPM and stops after a certain point.

how to fix?

  • Grab a partner and tell him to Turn the ignition key While your engine is hot.
  • Keep your ear close to the Solenoid
  • Listen for a clicking noise.

If you hear the clicking sound, the solenoid is working. Otherwise, you need to replace it. It may cost around $10 on Amazon.

Reason 5- Bad Kill Switch

Some riding mower models have a kill switch underneath the driving seat. And when your riding mower warms up, the kill switch stops making contact, which stops the engine.

READ: Craftsman 30-Inch Riding Mowers With Cutting Deck In (2023)

how to fix?

You can bypass the Kill Switch to get rid of this problem. But you will need a 12V Jumper Plug Connector for this process. Follow this method:

  • Go under the set and find the seat pressure/ Kill Switch.
  • Disconnect the two wires from the seat switch.
  • Secure the jumper in place with a zip tie.

However, you can also connect both wires, but doing so will void any warranty. So, jumper cable is a safer choice.

Reason 6. Clocked Carburetor Choke Plate

When the Carburetor choke plate gets dirty, it can’t properly flow the air and fuel, making the engine unresponsive. The Carburetor has many little holes. And if a tiny bit of dirt goes in those holes, the carburetor will stop working.

how to fix?

In order to resolve this issue, you will need to clean your carburetor. However, for this process, you have to open up your engine. So, if you are unsure of your mechanical skills, go to a service center; otherwise, follow the process below:

  • Turn off the fuel shutoff valve and remove the air filter cover by untwisting the fasteners.
  • Disconnect the breather hose and fuel line.
  • To remove the carburetor, take off the bolts and disconnect the solenoid wires.
  • Remove the bowl nut using a 14 mm socket.
  • Blow air through the needle valve hole to clear any dirt.
  • Clean the fuel inlet using Blow air.
  • Reassemble the carburetor, ensuring proper alignment.
  • Reinstall the carburetor on the mower and reconnect all hoses and wires.
  • Tighten all bolts securely.
  • Reinstall the air filter and cover.
  • Ensure proper alignment of all parts during reassembly.

After that, start your engine. Now, it will run without any issues.

in verdict: how To Maintain Your Lawn Mower For a Longer Run

Lawnmowers last a long time if you take care of them. While taking care of a lawn mower might be messy and take time, it’s important. Here are some pro-maintaining tips for your Lawn Mower:

  • Clean the mower after each use.
  • You should keep your mower blades sharp because dull blades tear the grass instead of cutting it, resulting in an uneven lawn and damaging your engine.
  • Check and change the oil according to your owner’s manual.
  • Inspect and replace the air filter every 6 to 12 months.
  • Store the mower with a full tank to stabilize fuel and prevent carburetor issues.

frequently asked questions [FAQs]

Usually, riding lawn mower owners have some common quarries about their equipment. I’ve collected some of those here with clear and understandable answers to assist you.

Is A Riding Mower The Same As A Tractor?

No, there’s a fundamental difference. Tractors have cutting blades at the center while riding mowers may differ in blade placement. And the mower blades are small and dense enough to cut the grass properly.

What Kinds Of Engines Do Lawn Mowers Use?

Depending on the model, lawn mowers generally use either two-stroke or four-stroke internal combustion engines.

Do Mowers Use Petrol Or Diesel?

Most lawnmowers use petrol, while diesel is mainly for commercial or heavy-duty machines like ride-on tractor lawnmowers.

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