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15 Reasons a Toro Zero Turn Won’t Start (Troubleshoot)

If only the grass would stop growing when your mower quits running. Because it doesn’t, you need to get your mower repaired soon or your yard will begin to look like a jungle.

A Toro zero-turn lawn mower won’t start when it isn’t getting sufficient 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, or a bad battery.

To minimize problems developing in your zero-turn, make sure you perform routine maintenance and use fresh gasoline. Prior to performing repairs, remove the ignition key and unplug the spark plug wires.

Toro zero turn won't start

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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 Toro Zero Turn Has a Starting Problem

1. Empty Gas Tank

I’m just mentioning this well-known fact that a gas-powered engine requires gas to run because you may have skipped over checking the tank.

SOLUTION: Add fresh fuel to an empty fuel tank.

2. Using Wrong or Old Gas

Correct Gas

Make sure you are not only using the right kind of gas for your mower but also make sure the gas is fresh.

Toro zero-turns require unleaded gasoline with a minimum octane rating of 87 and a maximum ethanol content of 10%. It’s important that you don’t use ethanol contents greater than this.

Ethanol, an alternative fuel that may be fine to run in most vehicles, is not good for small engines. Ethanol naturally attracts moisture from the air.

When the ethanol and moisture mixture evaporates, it leaves behind deposits that can damage fuel components and cause fuel restrictions.

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

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 Toro here.

Only Use Fresh Gasoline

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. This will help extend its shelf life.

Note: Fuel stabilizers only work when added to fresh gas. They cannot reverse the effects of old gas.

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.

3. Bad Spark Plug or Loose Connection

A dirty or bad spark plug can cause an intermittent spark. This can cause starting and running issues.

In addition, the spark plug must be gapped correctly and the spark plug wires must be securely attached. These items can also prevent your mower from starting.

SOLUTION: Remove the spark plug and inspect it. Replace the plug with a new one if you find it is very dark in color or it has a broken porcelain or burnt electrode.

If it is just a little dirty, but in overall good condition, you can clean it using a small wire brush.

Ensure the spark plug has a correct electrode gap. The gap specifications are set by the engine manufacturer. You can find these specs in the Toro operator’s manual.

Securely attach the spark plug wires once you have completed your repairs and are ready to start the mower.

4. Plugged Air Filter

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.

An air filter that isn’t regularly cleaned or replaced to keep it in good condition can cause a zero-turn to not start because sufficient air is not able to pass through a plugged air filter.

SOLUTION: Check and clean your paper air filter using these steps:

  • Remove the air filter cover,
  • Carefully remove the paper 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 see the light or you find the filter is extremely dirty or damaged.

5. Bad Fuel Pump

The fuel pump on your zero-turn may be the cause of your mower’s starting problem. The function of the fuel pump is to work against gravity and move 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. These types of pumps use the vacuum off the engine to draw fuel from the fuel tank.

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.

6. Plugged Fuel Filter

A fuel filter is installed between the fuel lines to strain the fuel as it comes out of the fuel tank and enters the fuel system.

The filter can become plugged with dirt over time keeping a good flow of fuel from passing through the fuel line.

I recommend replacing the fuel filter annually to ensure it stays in good condition.

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.

7. Clogged 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 Toro 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.

8. Clogged & Dirty Carburetor

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 an explosion, 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.

9. Bad Battery, Loose Cables, or Corroded Terminals

The starting system on a zero-turn requires the use of a battery to provide power to turn over the starter motor. Check the battery, cables, and connections when the mower clicks, hums or doesn’t make any noise when you go to start it.

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.

SOLUTIONTest your Toro 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.

Make sure all cables and components are secure and make good connections.

If you find any corroded components, safely remove the battery cables first. Then remove and clean any corrosion 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.

10. Bad 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 switchNever 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.

11. Faulty Ignition Switch

When you insert the key, turn it, and nothing happens, check the ignition switch.

SOLUTIONYou can use a multimeter to test the ignition switch. Replace the switch if bad.

12. Bad Starter Solenoid

A starter 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 the solenoid if it is found to be bad.

13. Bad Gas Cap

The gas cap’s purpose isn’t only to seal the fuel tank, it also provides a vent so air can pass in and out of the fuel tank.

When this vent no longer works, the air will form a vacuum when air isn’t able to pass through the cap into the fuel tank to equalize the air pressure in the tank and outside of the tank.

This vacuum will keep fuel from flowing out of the tank and to the carburetor. The engine will not be able to get gas to start the engine.

You may be able to identify a bad fuel cap by loosening the cap and then starting your Toro. If it starts, runs, and then begins to run sluggishly after you run it with the fuel cap tightened for a while, the problem may be with the fuel cap.

SOLUTION: Replace a bad fuel cap.

14. Faulty Charging System

While the charging system isn’t the main reason your Toro zero turn 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 go to 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 Toro dealership for troubleshooting and repair.

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.

15. Incorrect Starting & 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. 

This includes setting the parking brake and placing the speed levers in neutral before starting your Toro’s engine.

Still Having Problems with Your Toro Lawn Mower?

It would be great to own a problem-free lawn mower, but it’s never the case. No matter what brand mower you own, you’re going to run into problems the longer you own it.

To help you troubleshoot your mower problems, I have put together a list of common problems along with causes and solutions to fix them. Check out Common Toro Lawn Mower Problems and Solutions to learn more.