Fixed - Toro Lawn Mower Won't Start

By: Author John Cunningham. Published: 2019/02/02 at 7:17 am

Toro builds excellent machines; I know because I inherited an old Toro push mower that still runs like you wouldn’t believe.

So, your Toro lawn mower won’t start? A dirty carburetor is the most common cause of a Toro lawn mower won’t start. Other possible reasons include the following:

Fuel Valve Off
Choke Not On
Bad Gas
Plug Wet/Faulty
Plug Wire Off
Air Filter Blocked Carburetor Fault
Coil Fault
Bail Lever/Ignition Fault
Flywheel Timing (Shear-key)
Sticking Valves
Low Compression

This guide will help you quickly diagnose why your Toro lawn mower won’t start, restart, or stops when hot. Toro uses several different engine manufacturers – Briggs & Stratton, Kawasaki, Honda, and Toro engines.

This guide won’t cover each of these engine types, so your engine may look different from the ones used here. The diagnostic and repair procedures will be very similar regardless of your machine.

If you have a pull cord problem, I wrote a complete guide to repair all the most common issues – “Pull cord troubleshooting.”

Diagnosing a no-start Toro is pretty straightforward: carry out a few basic tests to eliminate ignition, fueling, and mechanical faults. Tests are not complex, but you must execute them correctly to avoid burning time or replacing parts needlessly.

This guide covers all the common causes of a no-start Toro pretty well. However, if you need more help, check out “Mower won’t start video.” It walks you through all the tests you’ll meet here in this post and includes a step-by-step guide to nailing your repair successfully.

There may be many other reasons why your Toro lawn mower won’t start. In this guide, we will cover all the most common faults.

Check the Basics

Before we go any further, let’s check all the basics. Sometimes, the easy answer is the solution or check out the “Common causes of no start video.”

The basics include:

Check for low oil; some mowers have a disabling system. Check out “How to check lawn mower oil”
Is the gas turned on? Check out “Where is my lawn mower gas tap”
Is the gas fresh? Gas older than one month is stale. Check out “Gas bowl drain video”
Is the choke on and working? Check out “How to start a lawn mower”
If the air filter is clean and dry, a gas-soaked filter will prevent starting. Check out “Mower tune-up guide”
Is the plug wire on securely?
Is the bail lever on and working OK? Check out “Hard to Start when hot”

That’s all the easy stuff checked; now we’ll dig a bit deeper.

3 Things Your Engine Must Have

Toro is a quality outfit. I have customers with 30-year-old Toro mowers still giving excellent service, so I know they can go the distance. The Toro mower engine is simple. It needs three things to run.

Thing 1

Fresh Gas – You must have clean, new gas. Old stale, or dirty gas, is by far the number one cause of all minor engine issues. This doesn’t guarantee that bad gas is your problem, but it’s one of the first things to check.

Thing 2

Spark – A well-gapped spark plug fired at the right time is as essential as good gas.

Thing 3

Compression – Piston rings, valves, and cylinder head gaskets help create compression; any problem here and the engine won’t run.

Each of these three systems will have many components, any of which could be the problem. Performing the following simple test will point us in the right direction.

You might find this page useful, “Small engine tools.” These are the tools I use; some of these will make your life a ton easier.

Try The Gas Shot Test

To quickly test if we have (1) Fueling, (2) Spark, or (3) Compression fault, we will bypass the fuel system, and we do this by pouring some fresh gas directly into the carburetor. This is the fastest way to diagnose which of the three systems has failed; it’s an elimination round.

For this test to be successful, you’ll need clean, fresh gas. If you are unsure of the quality, stop now, get fresh, and always in a clean, empty can. Fuel older than one month is likely stale.

In my workshop, fueling causes the most issues – stale or dirty gas, dirty carburetors, blocked filters, and the list goes on. When you identify which system has failed, you will be directed to the relevant repair guide, he said confidently.

Gas shot is covered here in the “Mower won’t start video.”

Remove – Remove the air filter cover and air filter; some will be fixed on with screws or wing nuts, and others will just pull off.

Shot – Pour some fresh fuel into the carburetor, about a cap full.

You’ll have to tilt your mower on its side to get the gas to flow in.

Pull – Now, attempt to start the mower in the normal way.

Two possible outcomes –

(1) Mower attempted to start or started – tells us we have a fueling fault, go ahead and test the choke system. (see below)

(2) Mower made no attempt to start – then we’ve likely eliminated a fueling fault, and the fault will probably be a lack of spark. Check out the “Spark test video” here or check out this post, “Mower won’t start no spark.”

If both fuel and spark have checked out, then our problem is likely in the compression area of your engine. Compression issues are usually related to wear and tear of the engine piston and rings; while replacing the rings is possible, it rarely makes economic sense to do so; more often, at this point, it makes more sense to go shopping for a new mower.

Try The Choke Test

In this guide, we will check that the choke systems are working correctly. As you know, the correct starting procedure for a cold engine will require giving it extra gas to enrich the fuel/air mixture, which a cold engine needs for a smooth start. Toro mowers are fitted with Briggs & Stratton, Honda, and Kawasaki engines. They use two different choke system types to achieve the enriched cold start mix.

If your Toro is pretty new, you’ll have an auto choke, and so you won’t have a lever to control choke. The choke test is covered in the “Mower won’t start video.”

Three types of choke are common: manual, auto, and primer bulb. Go ahead and identify which choke system is fitted to your Toro and check it’s working correctly. If all checks out ok, remove and clean the gas bowl.

To view the choke plate (if fitted), remove the air filter. When the choke is on, the choke plate should be fully closed. If not, check for cable adjustment.

Choke Plate – The first is the choke plate type – The manual version will have a lever to control the choke. There’s an auto choke version, and it won’t have a choke lever, but it operates similarly.

As the engine heats, the choke plate should be open (Choke off). Some auto choke carburetors give hot start flooding issues. Both versions of the choke plate type create a fuel-rich condition by reducing the amount of air and increasing the amount of fuel supplied to the engine.

Manual Choke On – If you have a manual choke control, move the throttle lever to the full choke position to start a cold engine. All current models are auto choke, and so won’t have a choke lever.

Manual Choke Off – Move the choke to the fast/run position as the engine warms a little. The choke should be off at this point. Check that it’s moving to the off position.

Auto Choke On – The auto choke system is controlled by a lever connected to a thermostat which is positioned close to the muffler or on the cylinder head. Check that it’s moving to the off position.

As the muffler warms up, the choke plate should open. Check its function. On some auto choke models, customers complain about hot start flooding issues.

The Fix – Drill a hole in the choke plate. Check for binding of the control links also.

Primer Bulb – The second type is the primer bulb – This is very simple and easy to use. It creates a fuel-rich condition by squirting extra fuel into the engine. You do this by pressing a rubber primer bulb mounted at the carburetor.

Check the bulb for damage; mice like to eat them. Replacement kits are available.

If all checks out OK, go ahead and remove and clean the gas bowl.

Clean The Carburetor Bowl

Cleaning the carburetor and fresh fuel will solve the problem of bad gas or a dirty carburetor. However, removing the carburetor can take time and effort. So, before we go down that road, we will try a quick fix. Removing and cleaning the fuel bowl & fuel feed bolt (Not all mowers have the fuel feed bolt) is something we can do with a minimum amount of effort and tools.

This may well solve your problem. I covered it below in pictures, or check out the “Mower won’t start” video for additional help. You won’t need any special tools for this job, but a carburetor cleaner can make life a lot easier. I use Gumout carb cleaner in the workshop; you can check it out here on the “Small engine tools page.”

I’ve listed a few other tools on this page, “Carburetor cleaning tools.” Cleaning the carb thoroughly is important. Nobody wants to visit the same job twice. These tools will help you nail it the first time out.

You can find your fuel bowl behind the air filter. I’ll show this process for the most common types of carburetors. Remember, if your gas is older than three months, it’s stale. So cleaning the bowl won’t make it go. You need to drain the tank and carburetor bowl and fill them with fresh gas.

Suppose this works out for you. Great! If not, I wrote this guide. It’ll walk you through the whole process – “Remove & clean carburetor.” Alternatively, it’s all covered in the “Mower won’t start video.”

If you’re not into cleaning the carburetor, I understand. Why not just change it? Carburetors aren’t expensive or difficult to replace. I’ve listed the most popular carburetors on the page, where you can check the price and availability of “New mower carburetors” or check out the Amazon link below.

Amazon Lawnmower Carburetors

Pull – When working on your mower’ remove the plug wire and turn off the gas. If you don’t have a fuel tap, use grips to gently squeeze the fuel line. This prevents a spill.

Briggs Gas Bowl – This is an older model Briggs and Stratton engine. The fuel bowl lives behind the air filter.

Your carburetor may look different; other examples are shown below. Remove the bowl using a 1/2″ socket and ratchet. Turn on the fuel to check that fuel flows from the carburetor. If not, move on to the fuel flow test.

Clean the gas bowl. This model has a fuel feed bolt; it’s a hollowed-out bolt that feeds gas to the carburetor jet. Be careful with the bolt gasket. The bolt must be clean; use a wire brush strand to clean it. Spray some carb cleaner up into the jet.

Check the large o-ring seal, which usually stays on the carburetor, and if so, that’s OK. Leave it there. If, however, it came off with the bowl, apply a small amount of oil to help it seat on the carburetor side.

When refitting, don’t over-tighten the bowl; this will cause the feed bolt gasket or the large o-ring to deform and leak.

If, after cleaning the bowl, the mower is still running rough, Check out “Remove and clean carburetor”

Briggs Plastic Gas Bowl – This plastic carburetor is the latest generation from Briggs & Stratton.
I use grips to gently squeeze the fuel line to prevent fuel spills.

The bowl drain plug is in the bottom of the fuel bowl. Remove it; some can be tricky as clearance is poor. If you are struggling to gain access to the drain plug (Black hex head), go ahead and remove the two bowl retaining bolts.

Use a flat screwdriver to pry off the bowl.

Now, pry out the fuel jets. Use a fine wire to clean them. Be careful with compressed air, as the little brass jets will fly and be lost forever. With the bowl removed, remove the grips from the fuel line and check fuel flows from the carburetor; if not, move on to the fuel flow test.

Rebuild in reverse order after cleaning.

If cleaning isn’t successful, order a new jet pack. There are a few different types, so have your engine number handy.

Honda Gas Bowl – This type of bowl is fitted to the Toro and Honda engines. Honda has fitted a drain bolt that allows you to drain the fuel from the bowl. Nice! This is great if the bowl has some bad gas in it.

However, if the bowl has some grit, it won’t drain out completely. So best to remove the bowl and clean it thoroughly. Turn on the fuel and check that you have fuel flow from the carburetor; if not, move on to the fuel flow test.

If the mowers are still running rough after cleaning the bowl, Check out “Remove and clean carburetor” or check out the “Carburetor cleaning video” here.

If none of this helped, go to the “Mower won’t start video” page and start at the beginning; the solution is there.

Tune-up Your Toro

To get the best from your Toro, you should service at least once per season, ideally in the spring. The tune-up kit includes oil; plug; air filter; fuel filter (if fitted); new blade (optional). Doing a tune-up is simple. This guide will have your mower tuned up in under an hour – “How to Tune-up your mower.”

You will need your engine model code. It’s stamped on the body of the mower or on the engine. Briggs and Stratton stamp their codes into the metal valve cover at the front of the engine. Kohler has a tag, and Honda has a sticker on the engine.

After you find these numbers, buying the tune-up kit online is easy. Suppose you can’t find the code – no problem. Remove the air filter and match it against a tune-up kit listed online. Most mower engines are very common, so you won’t have a problem getting a tune-up kit to match.

A full tune-up, including blade balancing and sharpening, is covered in the “Mower tune-up video.” Tune up once per season at the start of the season. If your mower is new, change the oil after the first 5 hours of use.

The Problem With Gas

Most manufacturers are OK with e10. This has a 10% ethanol blend. E15, on the other hand, is not OK. Ethanol is an alcohol fuel made from sugar, corn, and other plant materials. The alcohol is then blended with gas to make ethanol.

What Manufacturers Say

Some manufacturers claim that the alcohol content of the ethanol will damage the carburetor’s plastic and rubber components. E15 and E85 burn hotter than regular gas. Your mower is not designed to run at these temperatures. Using these types of fuels will damage your engine and void your manufacturer’s warranty.

What Toro Say

Toro advises using ethanol-free gas with an 87-octane rating. The max ethanol blend advised is E10, and methanol is a no. They also advise the use of a fuel stabilizer.

A stabilizer will keep your gas fresh for up to 2 years. You can mix it with your gas and use it all the time, but I only use it towards the end of the season and when winterizing all my gas-powered kit, including two-stroke. A few drops in the gas tank are all it takes.

I use a product called Sta-bil gas,1 ounce treats up to 2.5 gallons; it prevents gumming and cleans the fuel system. Using a gas stabilizer is covered in the gas stabilizing video here, and you’ll find a link to the stabilizer I use here.

The Problem With Ethanol

It absorbs moisture from the atmosphere. If the fuel is left in the mower over the winter, the moisture collects in the carburetor. The water will often corrode and leave a varnish-type deposit that blocks up the ports. This is what causes the poor running/no start.