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Toro Lawn Mower Won’t Start: Why and How to Fix

Last weekend, I decided it was finally time to tame my wildly overgrown lawn. But as luck would have it, my trusty Toro lawn mower stubbornly refused to start. Ever been all set for a day of yard work, only to be thwarted by a silent mower?

A common reason for a Toro lawn mower not starting is a dirty or clogged carburetor. Over time, old fuel can leave behind residues that hinder the carburetor’s function. Cleaning the carburetor thoroughly can often solve this issue.

Another possible cause for a Toro lawn mower not starting is a faulty spark plug. A spark plug that’s dirty or has become disconnected can prevent the mower from starting. Remove the spark plug, clean it with a wire brush, and check the gap. Reconnect it securely, or replace it if it’s damaged or worn out. This simple fix can often bring your mower back to life.

In this article, we will go through all possible reasons for a Toro lawn mower’s engine not starting. We will also discuss the various ways through which these potential problems can be remedied. Now let’s dive in!

Check if the Carburetor Is Dirty

The first thing you need to check if your lawn mower won’t start is if the carburetor is dirty. This is because too much dirt can reduce the required amount of air and fuel, which is supposed to travel through the passage of the engine. 

Dirt and fuel residue can bog down a carburetor, so it is essential to maintain it from time to time. Apart from the mower refusing to start, some other common symptoms of a dirty carburetor are hard starting, stalling, hesitation, rough idle, and flooding. 

How to Fix

  1. You will first need to remove the outer paneling of the mower, where you will find the air filter and carburetor. 
  2. Unbolt the carburetor and disconnect it from the fuel line.
  3. Unbolt the bowl by removing the nut that holds it in place. After removing the nut, clean the hole and check for any debris inside the jet. 
  4. You can use a cleaning spray or liquid, which is meant for carburetors to clean the entire carburetor. 
  5. Once you’ve finished, assemble the device back together.

Check for a Faulty Carburetor

A carburetor helps supply fuel to the engine. Without this, it is impossible for an engine to function normally. The problems that occur when a carburetor is faulty include hesitation, stalling, rough idle, flooding, and a few similar problems. 

Before diagnosing your carburetor as being faulty, here are some of the main symptoms that reflect a bad carburetor:

  • Reduced engine performance
  • Black smoke coming from the exhaust
  • Backfiring
  • Overheating
  • Hard starting

If you notice any of these problems along with the mower refusing to start, you can be sure that the carburetor is the problem.

How to Fix

  1. Start by disconnecting the spark plug wire and then remove the air filter housing.
  2. Make sure to drain the fuel tank into a container before proceeding.
  3. Remove the blower housing, after which you’ll be able to access the carburetor.
  4. Once you’ve removed the carburetor, you can install a new one and then reassemble the mower.
  5. Be sure to check with a professional before proceeding with this process as the procedures might vary from model to model.

To help you understand the process better, here’s a video that demonstrates the process of changing a carburetor in a Toro Recycler Push Mower:

Check if the Fuel Valve Is On

The fuel valve prevents gas from leaving the tank and entering the lawn mower’s engine. If there is a blockage or leak in the valve, it can cause compression problems and prevent the engine from starting. 

Additionally, a fuel valve prevents the engine from flooding when it is being transported. So if the fuel valve is shut off, it cuts off fuel flow to the engine compartment.

How to Fix

  1. Find the fuel line switch, which is usually located at the base of the fuel tank where the fuel line and the tank connect. 
  2. If the valve is off, turn it on.

Check if the Choke Is On

The correct fuel-air mixture is important when starting an engine, and a choke valve is usually installed in the carburetor of lawn mowers to restrict the flow of air. Most chokes are automatic, but some are manual and will need to be turned on and off accordingly. 

How to Fix

  1. If your choke is manual, make sure it is turned on when you start the engine. 
  2. The choke is usually found on the carburetor beside the engine, but it might be found elsewhere in different models.
  3. The choke must usually be pushed down for it to be in the open position.
  4. Remember to turn the choke off after the engine has been running for several seconds.

Check for Bad Gas

If your lawn mower won’t start, bad gas can be one of the reasons for this problem. Old and empty gas tanks and cans sometimes may contain old gas deposits, which can contaminate and mix with new gas. These deposits can later clog the carburetor, fuel line, and fuel filter. 

The best way to check if the gas is bad is through a simple smell test. Bad gas generally has a sour and strong smell when compared to the smell of fresh gas. If this doesn’t work, you can drain your gas into a clear container and check the color of the gas. If it is very dark, it has most likely gone bad.

How to Fix

  1. It is vital that you remove all traces of the bad gas from your lawn mower before you refill it with good gas.
  2. After draining most of the gas from the fuel line, use rags to soak up the residue and the remaining gas from the bottom of the tank.
  3. Add a little fresh gas to the tank and slosh it all around before you drain this gas along with the bad gas.
  4. Allow the tank to dry completely.
  5. Refill the tank once this process has been completed.

Check for a Wet or Faulty Spark Plug

The spark plug is responsible for the ignition of the fuel, which causes combustion in the engine. So if it stops working, your lawn mower can experience a number of issues.

The most common symptom of a faulty plug is the engine refusing to start. 

An engine requires two things to start, gas and spark. So if your tank is filled with gas, it is most likely a fault in the spark plug.

To know if the spark plug is bad or faulty, inspect the plug for deposits and cracked electrodes or porcelain. Additionally, a damaged spark plug might also be wet, which can lead to long-term damage in the engine if not fixed immediately.

How to Fix

  1. You can try cleaning the plug if you only find deposits on its surface. This can be done by using a plug spray cleaner and a soft cloth to wipe away the dirt. 
  2. However, if you notice any other signs of damage, replace the spark plug immediately.
  3. Experts suggest replacing the spark plug after 25 hours of usage on a lawn mower. While this may not always be necessary, you should replace it at least once a year.

Check if the Plug Wire Is On

Sometimes, a spark plug wire can pop out of the spark plug due to becoming loose over time. This causes the combustion gasses to cause pressure, resulting in the plug wire coming off. 

When this happens, it is best to replace the plug wire before it becomes worse. Additionally, you must also replace the plug wire if you notice it is old and rusty.

How to Fix

  1. Consult with a professional, as some plug wires can be fixed and do not need to be replaced if the damage is minimal. This will save you some money in the long run.
  2. If the wire is beyond repair, then consider changing it immediately. The procedure can be a little complicated, so it is best to hire a professional.

Check if the Air Filter Is Blocked

An air filter is used to prevent dust and dirt from entering the carburetor. In the process, the air filter might get clogged with debris over time, which in turn will prevent the passage of air into the carburetor. This can prevent the engine of the lawn mower from starting. 

Some other symptoms of a clogged air filter are black sooty smoke from the exhaust, dirty appearance of the air filter, a smell of gasoline, and backfiring. If all these problems occur, you can be sure that the problem lies with the air filter being blocked or clogged.

How to Fix

  1. Disconnect the spark plug wire and remove the air filter cover.
  2. Clean the foam with compressed air or rinse it with water.
  3. Discard the old paper filter and replace it with a new filter.
  4. Replace the air filter cover.

Cleaning the air filter is a fairly simple job, so you needn’t necessarily hire a professional for it.

Check for a Faulty Coil

One of the main symptoms of a faulty ignition coil in a lawn mower is excessive heating of the mower and the inability of the machine to start. A faulty coil can cause a mower to refuse to start, or start and shut off once it has run for a few minutes.

If a coil fails completely, it results in a no-spark condition, which prevents the engine from starting. It is best to replace the coil once you realize it has become bad. 

Copyright article owner is for this article. This post was first published on August 26, 2020.

How to Fix

  1. Before replacing the coil, check if it is bad using an ohmmeter, as that will remove the possibility of the fault lying in some other part of the motor. 
  2. First, disconnect the spark plug wire.
  3. Next, remove the blower housing and then remove the ignition coil. 
  4. Replace it with a new ignition coil.
  5. Reinstall the blower housing.
  6. Reconnect the plug wire.

Check for a Malfunctioning Bail Lever 

Most lawn mowers have a bail or a lever on the handle, which allows them to start the engine. This is because the bail or lever is attached to a cable, which in turn is attached to the ignition switch. 

You need to know that an ignition switch is in the off position when an engine is running and is on when the mower is stopped. When the mower is running, it is the bail lever that holds the ignition switch in the off position. Sometimes, there can be a problem with the bail or with the switch, causing it to remain in a stuck position. This will then prevent the engine from getting turned on.

How to Fix

  1. Check the lever and the cable, which is attached to the ignition switch for any signs of damage or breakage.
  2. If you find that the cable has been damaged (which is most commonly the problem), simply reinstall a new cable. 
  3. Also, check for any signs of a loose connection in the lever and the ignition switch.

Check the Flywheel Key

If your mower refuses to start or fires weakly before it stops, the problem could be with the flywheel key. A flywheel key is used to protect the crankshaft from twisting, which could lead to more severe damages in the mower. A flywheel helps protect the crankshaft when the mower blades cut through hard objects like tree stumps and barks and such.

However, if the blade is loose, the flywheel key can get sheared too. This, in turn, will cause the engine timing to be incorrect and lead to other complications.

The only way to fix this problem is by replacing the flywheel key with a new one.

How to Fix

  1. Remove the gas tank and set it aside.
  2. Next, loosen the flywheel and remove it.
  3. Be sure to remove all the fragments of the old key.
  4. Then you can proceed to install the new key and flywheel.
  5. Be sure to reassemble the mower once again.

Check for Sticky Valves

Infrequent oil changing and heavily-leaded fuels can lead to the valve becoming sticky. Since valves are in control of the flow of fuel vapor into the combustion chamber and also helps exhaust gases leave the engine, dirty valves that are sticky can cause the engine to lose its power and fuel efficiency. In some cases, it can lead to the mower refusing to start as well.

How to Fix

  1. To know whether or not the valve is stuck, try rotating its head with a screwdriver. It should be able to move easily, so if you face resistance, you can be sure that your valve is stuck.
  2. Soak the sticky valve with penetrating oil for several minutes. 
  3. Once the valve has been loosened up because of the lube, push the valve down with your hand. This will free up the valve stem shaft and help it move properly. 
  4. Replace the valve covers once you have finished.

Check for Low Compression

Most lawn mowers require 90 PSI of compression when hot and 100 PSI when cold. If there is an air leak in the engine, it will lead to low compression. If there is no compression in all cylinders, this will result in the engine refusing to start.

How to Fix

  1. Check if the spark plug is loose, as that can cause the compression to leak. Tighten it with a ratchet and check if the engine works.
  2. If your valves or piston rings are worn, replace them.
  3. If the cylinders lack compression, you will have to fix this with the help of a professional, who will replace the chamber cylinder heads and gaskets if they are faulty.

Final Thoughts

This article gives a detailed list of all the possible causes for a Toro lawn mower refusing to start.

Be sure to check all symptoms of the possible problems mentioned above before implementing any of the solutions to fix the defective parts. Additionally, replace a part only when you’re absolutely sure that it is the cause of the problem. Good luck with fixing your lawn mower!

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ReadyToDIY is the owner of this article. This post was published on August 26, 2020.

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