Toro Lawn Mower Won't Start

What We'll Cover

Toro Lawn Mower Won't Start

What We'll Cover

Causes

01. Fuel Valve Off

02. Choke Not On

03. Bad Gas

04. Plug Wet/Faulty

05. Plug Wire Off

06. Air Filter Blocked

07. Carburetor Fault

08. Coil Fault

09. Bail Lever/Ignition Fault

10. Flywheel Timing (Shear-key)

11. Sticking Valves

12. Low Compression

Most Common Cause

The most common reason a Toro mower won't start - Gummed up carburetor. 

 

This guide will help diagnose quickly, why your Toro lawn mower won't start, restart, or stops when hot. Toro use several different engine manufactures - Briggs & Stratton, Kawasaki, Honda and Toro engines. 

 

This guide won't cover each of these engine types, and so your engine may look different to the ones used here. The diagnostic and repair procedures will be very similar no matter which engine you have.

 

If you have a pull cord problem, Check out "Pull cord troubleshooting" 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 lets check all the basics. Sometimes the easy answer is the solution. 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 clean out"

Is the choke on and working? Check out "How to start a lawn mower"

Is the air filter clear 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.

 

Engine Must Have

Toro are a quality outfit, I have customers with 30 year old Toro mowers still giving great service, so I know they can go the distance. The Toro mower engine is simple, it needs 3 things to run.

 

Thing 1, Fresh Gas - You must have clean fresh gas. Old stale or dirty gas is by far the number one cause of all small engine issues. This doesn't gurantee that bad gas is your problem, but it's one of the first things to check.

 

Thing 2, Spark - A well gapped spark plug and fired at the right time, this is as important 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 3 systems will have many components, any of which could be the problem. Performing the following simple test will point us in the right direction.

 

 

 

 

Gas tank

Thing 1, Gas

Thing 2, Spark


Spark plug
Mower engine test

Thing 3, Compression

Thing 1, Gas


mower tank

Thing 2, Spark


mower carburetor

Thing 3, Compression


mower carburetor

Gas Shot Test

To quickly test if we have: (1) Fueling (2) Spark (3) Compression fault. We will by pass 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 3 systems have failed, it's an elimination round.

 

For this test to be successful, you'll need clean fresh gas. If your unsure of the quality, stop now and get fresh, and always in a clean empty can. Fuel older than 1 month is 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.

 

 

Remove


Mower air filter

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

Shot


Mower carburetor

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


Mower start

Now attempt to start the mower in the normal way.


Mower black smoke

Two possible outcomes -

(1) Mower attempted to start or started - tells us we have a fueling fault.  Check out "Choke system"

(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 "Spark system check"

Mower air filter

Remove

Remove air filter cover and air filter, some will be fixed on with screws or wing nuts, 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.


gas stabilizer
Mower starting

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.  Check out "Choke system"

(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 "Spark system check".


gas stabilizer

Choke Test

In this guide we will check that the choke systems 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. 

 

 

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 in the same way, 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.

 

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

 

 

mower throttle lever mower carburetor

Manual Choke On

If you have a manual choke control, move throttle lever to full choke position to start a cold engine. 

Remove the air filter, this allows you view the choke plate, seen here in the choke fully on position.

The plate should be fully closed, if not check cable adjustment.

Manual Choke Off

As the engine warms a little, move the choke to the fast/run position. The choke should be off at this point.

Check that it's moving to the off position.


mower throttle lever mower carburetor
mower auto choke mower choke plate

Auto Choke On

The auto choke system is controled by a lever connected to a thermostat which is positioned close to the muffler or on the cylinder head.

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.

Manual Choke On


Mower throttle lever Mower carburetor choke plate

If you have a manual choke control, move throttle lever to full choke position to start a cold engine. 

Remove the air filter, this allows you view the choke plate, seen here in the choke fully on position.

The plate should be fully closed, if not check cable adjustment.

Auto Choke On


Mower carburetor Mower choke plate

The auto choke system is controled by a lever connected to a thermostat which is positioned close to the muffler or on the cylinder head.

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.

 

So go ahead and identify which choke system is fitted to your Toro and check its working correctly. If all checks out ok go ahead, remove and clean gas bowl.

 

 

 

Primer


Mowerprimer bulb

It's a simple system, pressing the bulb injects extra fuel - check the bulb for damage, mice like to eat them. Replacement kits are available.

Carburetor primer

Primer

It's a simple system, pressing the bulb injects extra fuel - check the bulb for damage, mice like to eat them. Replacement kits are available.

Bowl Clean

Cleaning the carburetor and fresh fuel will solve the problem of bad gas or a dirty carburetor. But removing the carburetor can take time and effort. So, before we go down that road, we'er going to 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 minimum amount of effort and tools. This may well solve your problem. A can of carburetor cleaner will make this job a whole lot easier.

 

You can find your fuel bowl behind the air filter. I will show this process for the most common types of carburetor. 

 

Remember, if your gas is older than three months, its stale. So cleaning the bowl won't make it go. You need to drain the tank, carburetor bowl and fill with fresh gas.

 

If this works out for you great!  If not, check out  "Remove & clean carburetor".

 

 

 

Bowl Bolt


Mower plug wire Mower gas line

When working on your mower' remove the plug wire and turn off the gas.

If you don't have a fuel tap use a grips to gently squeeze the fuel line. This prevents a spill.

Pull

When working on your mower' remove the plug wire and turn off the gas.

If you don't have a fuel tap use a grips to gently squeeze the fuel line. This prevents a spill.


Mower plug wire Mower gas tap

Briggs Bowl Clean


mower engine mower carburetor mower carburetor mower carburetor bowl mower carburetor bowl mower bolt clean mower carburetor 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 carburetor, if not move on to 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, 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 dis-form and leak.

If after cleaning the bowl the mowers still running rough, Check out " Remove and clean carburetor"

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 carburetor, if not move on to 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, 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 dis-form and leak.

If after cleaning the bowl the mowers still running rough, Check out " Remove and clean carburetor"


Mower gas bowl Mower gas bowl Mower gas bowl Mower gas bowl Mower gas bowl feed bolt Mower gas bowl feed bolt

Briggs Bowl Clean


Mower Carburetor Mower Carburetor Mower Carburetor Mower Carburetor Mower Carburetor Mower Carburetor

This plastic carburetor is the latest generation from Briggs & Stratton.

I use a grips to gently squeeze the fuel line to prevent fuel spill.

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

With the bowl removed, remove grips from fuel line and check fuel flows from the carburetor, if not move on to fuel flow test. 

Use a flat screwdriver to prise off the bowl. Now prise out the fuel jets.

Use a fine wire to clean them. Do be careful with compressed air, as the little brass jets will fly and be lost forever.

If cleaning isn't successful, order a new jet pack. Few different types, so have your engine number handy.

mower carburetor mower carburetor

Briggs Gas Bowl

This plastic carburetor is the latest generation from Briggs & Stratton.

I use a grips to gently squeeze the fuel line to prevent fuel spill.

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

mower gas bowl bolt mower gas bowl bolt mower carburetor mower carburetor mower carburetor jet pack

With the bowl removed, remove grips from fuel line and check fuel flows from the carburetor, if not move on to fuel flow test.

Use a flat screwdriver to prise off the bowl. Now prise out the fuel jets.

Use a fine wire to clean them. Do be careful with compressed air, as the little brass jets will fly and be lost forever.

If cleaning isn't successful, order a new jet pack. Few different types, so have your engine number handy.

Honda Gas Bowl

This type bowl is fitted to the Toro and Honda engines.

Honda have fitted a drain bolt which allows you 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 fuel and check that you have fuel flow from the carburetor, if not move on to fuel flow test.

If after cleaning the bowl the mowers still running rough, Check out " Remove and clean carburetor"


mower carburetor mower carburetor mower carburetor

Honda Gas Bowl


Mower gas bowl Mower gas bowl Mower gas bowl

This type bowl is fitted to the Toro and Honda engines.

Honda have fitted a drain bolt which allows you 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 fuel and check that you have fuel flow from the carburetor, if not move on to fuel flow test.

If after cleaning the bowl the mowers still running rough, Check out " Remove and clean carburetor"

Tune-up

To get the best from yourToro, you should service at least once per season, ideally in the spring. Tune-up kit includes: oil; plug; air filter; fuel filter (if fitted); new blade (optional). Doing a tune-up is simple, check out this simple guide "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 have a tag and Honda have sticker on the engine.

 

After you find these numbers, buying the tune-up kit on line is easy. If you can't find the code - no problem. Remove the air filter and match it against a tune-up kit listed on-line, most mower engines are very common and so you won't have a problem getting a tune-up kit to match.​​ Or check out "Toro parts lookup".

 

 

 

Mower tune-up kit Mower tune-up kit

Tune-up

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.

Tune-up Kit


Mower tune-up kit Mower engine number

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.

Ethanol Gas

Most manufactures 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 manufacturers warranty.

 

What Toro Say

Toro advise using ethanol free gas with an 87 octane rating. The max ethanol blend advised is e10, and methanol is a no, no. They also advise the use of a fuel stabilizer. Check out "Toro fuel facts".

 

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 which blocks up the ports. This is what causes the poor running/no start.

 

 

Gumming


Mower carburetor gumming Mower gas stabilizer

Remove plug wire and turn off fuel as before. Loosen bolt on the fuel bowl. Remove the air filter clean or replace before refitting.

Gumming

It's a carburetor killer, using a gas stabilizer will prevent a lot of problems.


Mower carb Mower carb