15 Reasons a Zero Turn Won’t Start (Complete List)

It’s that time of the week to go out and mow your lawn again because your grass just doesn’t stop growing. The only problem is, this time, the mower doesn’t want to start.

A zero-turn lawn mower won’t start due to a lack of fuel, air, or spark. This is caused by old gas, a bad spark plug, plugged air filter, plugged fuel filter, a clogged fuel line, a dirty carburetor, a bad starter solenoid, a bad gas cap, and a bad battery.

It’s good practice to keep your zero-turn serviced to minimize problems and increase its life. Always follow the safety instructions provided in the operator’s manual.

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

15 Reasons Your Zero Turn Mower Has a Starting Problem

While the items listed will keep your mower from starting, if you’re not following the right steps to start your zero-turn, you’ll also have problems.

If you need help with the steps to start a zero-turn, check out this article.

Zero Turn Fuel Tank is Empty

I’m just going to quickly mention this fact as you already know your need fuel, but just in case you forget to check your fuel tank to ensure an adequate fuel supply.

Solution: Add fresh fuel to an empty fuel tank.

Using the Wrong Type of Gas or Old Gas in Your Zero Turn Mower

Correct Gas for a Zero-Turn Lawn Mower

When operating a gas-powered zero-turn mower, make sure you are using the right kind of gas in your mower. Ethanol, a corn-based product, is added to fuels today to make our fuels more environmentally friendly.

While ethanol may be okay to run in your car or truck, it is not good for the small engines used on zero-turn mowers. Zero-turns require unleaded gasoline with a minimum octane level of 87 and a maximum ethanol content of 10%.

Be careful when purchasing fuel at your local gas station. Fuels containing ethanol levels of 15% and 85% are appearing at more gas stations, known as E15 and E85 fuel respectively.

Using gasoline with this high ethanol level can cause significant engine damage. You can find more information about the correct gas to use in your zero-turn here.

Only Use Fresh Gasoline in Your Zero Turn

Because gasoline begins to break down and becomes less effective as soon as 30 days, it is important to buy gas from a busy gas station. Ethanol in gasoline attracts moisture which can cause run ability issues and gum the fuel system.

If you have more than a 30-day supply of fuel on hand, use a fuel additive to stabilize your fuel and reduce moisture buildup.

Solution: If you have purchased the wrong type of fuel and placed it in your zero-turn fuel tank, drain and flush the fuel tank. A manual siphon pump works well to drain the tank.

Add fresh gasoline that includes a fuel additive to stabilize and clean your fuel system like Sea Foam. Read more about the advantages of using Sea Foam Motor Treatment in your zero-turn.

Zero Turn Gas Cap Won’t Vent

Something as simple as a bad gas cap can cause your mower not to start. Your zero-turn gas cap is designed with a vent to allow air to pass through the cap.

When this vent is clogged, a vacuum is formed in your fuel tank. This vacuum restricts fuel from leaving the tank causing your mower not to start because the carburetor isn’t getting gas.

You may be able to identify a plugged cap by running your mower with and without the cap. Confirm the mower starts and runs without the cap and dies after a short period once the cap is installed to determine you may have a bad cap.

Solution: You can try to clean and remove the clog in your cap. If you are unsuccessful, replace your gas cap.

Bad Spark Plug or Loose Connection on Your Zero Turn

When your spark plug wires are loose or the gap is set incorrectly, you may have intermittent running or starting issues with your zero-turn. Dirty spark plugs can also foul out causing the same problem.

Check your spark plug to ensure your starting issue on your zero turn isn’t due to the spark plugs.

Solution: Remove your spark plug and inspect it for signs of carbon buildup or a cracked porcelain insulator. Replace with a new spark plug(s) if they are damaged.

Clean the tips if they are dirty. Make sure the spark plugs are correctly gapped and the wires are secure.

Air Filter Plugged in a Zero Turn Mower

Using a clean air filter not only allows your engine to get the clean air it requires but also prevents dirt from entering the cylinder and causing significant damage to the engine.

Running an air filter that is very dirty can keep your mower from starting when the engine can’t access the air.

Solution: Check and clean your air filter using these steps:

• Remove the air filter from the filter housing.
• Don’t let any dirt fall into the air intake. Wipe out any excess dirt that remains in the filter housing with a dry cloth.
• Tap your air filter against a solid surface to release as much dirt as you can remove.
• Hold the filter up to a light source and check for light shining through the paper element.
• Reuse the filter if you can see light. Replace your filter with a new filter if you cannot.

Zero Turn Fuel Pump is Bad

The fuel pump on your zero-turn may be the cause of your zero-turn not starting. The function of the fuel pump is to work against gravity and pump fuel up to your carburetor.

When it fails, the carburetor doesn’t receive the fuel it needs and the engine is unable to start. A carburetor can fail over time.

Most zero-turn mowers use a vacuum-style fuel pump. Over time, fuel can cause your fuel pump to degrade. A pump that is no longer able to hold the pressure required to pump fuel must be replaced.

If the fuel pump is leaking fuel, you must replace it. When you can’t see any visible signs of damage to your pump, perform a couple of tests to identify a pump problem:

• Shut off your fuel supply using the fuel shut-off valve under your fuel tank or use clamps to pinch the fuel line to stop the flow.
• Remove the hose from the inlet port on the pump. Place it in a container placed lower than the fuel tank so fuel can flow into the container using gravity. This step is to confirm your fuel pump is getting the fuel.
• Start your fuel flow. If you are getting flow into the container, you have confirmed you are getting fuel flow to the pump. If you are not, you have a fuel restriction you need to locate prior to the pump.
• Shut off the fuel flow. Replace the hose on the inlet port.
• Remove the hose from the carburetor and place it in a container so you can confirm the condition of your fuel pump.
• Start your fuel flow and start your engine. Watch for a steady or pulsating flow of fuel out of the fuel line.
• Once your test is done shut off your mower and reattach your fuel hose to the carburetor.

Solution: Replace your fuel pump on your zero-turn if you are not receiving a constant or pulsating flow out of the pump.

Plugged Fuel Filter in Your Zero Turn Mower

A fuel filter can get plugged with dirt and deposits from your fuel. Check your fuel filter for clogging. I highly recommend you replace your filter once a year when completing your zero-turn maintenance so you don’t run into this problem.

Solution: A clogged fuel filter must be replaced with a new one. Make sure you install it correctly with the arrow on the filter pointed in the direction of the fuel flow.

Blockage in Your Zero Turn Fuel Line  

You may have found a blockage in your fuel line when you were testing your fuel pump. Blockages in your line can be isolated by starting and stopping fuel flow while checking sections of your fuel line.

Solution: Once you find a clogged line, try to remove the blockage. To do this, remove the line from your zero-turn.

Spray carburetor cleaner into the line to try to loosen the blockage. Follow the carb cleaner with compressed air blown into the line to remove the clog.

If you are unable to dislodge the clog, Replace the fuel line making sure you purchase the right size diameter of the fuel line. I do recommend replacing your fuel lines, even if you don’t find a clog in them if your fuel lines are dry and beginning to crack.

Clogged & Dirty Carburetor on Your Zero Turn

A dirty carburetor can be the cause of your zero-turn will not start and run. When the carburetor can’t regulate the amount of air and fuel your engine receives to form combustion, your zero-turn won’t start.

Old fuel can cause gummy and crusty deposits to form in your carburetor that can cause the small components in your carburetor to stick not allowing it to function correctly.

When your carburetor does not work properly, you will have to clean the carburetor and replace any stuck or damaged parts that are unable to be cleaned.

Solution: I have listed steps for cleaning your carburetor here. Follow these if you have a little mechanical ability and are comfortable working with small parts.

If you do not what to attempt cleaning or rebuilding your carburetor, you can take your mower to your small engine repair shop to be cleaned or you can replace it with a new carburetor assembly.

Bad Zero Turn Mower Battery, Loose Cables, or Corroded Terminals

A bad battery, loose cables, or corroded terminals can all cause your zero-turn to not start. Make sure the battery terminals are securely in place and not corroded. Also, check your battery to confirm it is charged and can continue to hold a charge.

Solution: Test your zero-turn battery with a multimeter. If your reading is less than 12.7 volts, place your battery on a battery charger. Replace your battery if you find it will no longer hold a charge. Read more about the steps and items needed to charge your battery here.

If you find your battery terminals are corroded, clean them with a baking soda solution containing 2 cups of water and 3 rounded tablespoons of baking soda. Use a wire brush to scrub the terminals clean.

Bad Zero Turn Safety Switch  

Your zero turn has an operator presence control system installed to keep you safe. A safety switch can be defective and cause your zero-turn to fail to start.

Solution: Test your switch using a multimeter. You can also temporarily bypass the safety switch to identify a bad switch but only do this for troubleshooting purposes.

Never operate a mower without the safety switch. Never run a mower when a safety switch is bypassed. A safety switch can save you from serious injury and you never know when you’re going to need it.

Bad Zero Turn Ignition Switch or Ignition Coil 

The ignition switch or ignition coil could be the problem when you insert the key and find it fails to start.

Solution: You can use a multimeter to test the ignition switch. Replace the switch if bad.

Bad Starter Solenoid on Your Zero Turn

A lawn mower solenoid is an electromagnetic switch that is like an on-off switch that actuates the starter motor to turn over the engine. A click or hum when turning your ignition key is an indication to check your solenoid.

Another indication your solenoid may be bad is when a wire attached to your solenoid gets hot and begins to smoke or melt.

Solution: Test your solenoid by following the steps here. Replace your solenoid if it is found to be bad.

Faulty Charging System on Your Zero Turn Mower

While the charging system isn’t the main reason your zero-turn mower won’t start, it can contribute to a weak battery that prevents the mower from starting.

When the charging system fails to charge the battery, the battery may not be able to start the mower the next time you use it. A bad stator or alternator can be the problem along with several other electrical parts. Read this article to test your charging system here using an ohmmeter. 

Solution: Once you identify the problem that lies in your charging system, my advice to you is to bring it to your local zero-turn mower dealership for troubleshooting.

There are many components that make up the charging system. Without the experience, you will most likely be throwing parts at your mower hoping to find the problem.

Electric parts on your lawn mower can be expensive. Most likely, electric parts are non-returnable. So, if you find the expensive part you bought is not the problem, you are stuck with it.

Incorrect Zero Turn Operating Procedure  

Zero-turn mowers have safety procedures that require certain steps to be followed when starting and operating the lawn mower.

Solution: Refer to your mower’s operating manual to ensure you are operating your lawn mower correctly so you don’t set off the safety features that shut off your lawn mower.