After the investment you made into purchasing your SCAG mower, it’s frustrating when it just stops running. No matter what brand mower you purchase, there will be a time during the lifespan of the mower when it just quits.
A SCAG lawn mower will start and then die when the air filter is plugged; the fuel flow is restricted; the spark plug is dirty; the engine oil level is too high or too low; the engine is put under an increased load, or the engine overheats.
Keep reading for more causes of a SCAG mower shutting down and dying. Consult a professional mechanic when you are unsure of any steps required to diagnose and repair your mower safely.
If you narrow your problem down to an internal engine problem, it’s best to have a small engine mechanic diagnose and make the necessary repairs.
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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.
This is Why Your SCAG Lawn Mower Starts Then Dies
Bad or Old Fuel
Even if you choose the right gas for your SCAG mower, you must properly store and use that gas timely. Gas can begin to break down and become less effective as quickly as 30 days after you purchase it.
Running old gas through your mower can negatively impact its performance. It can cause components to fail and create fuel restrictions.
Most gas contains a product called ethanol to make gas more environmentally friendly. This is an alternative fuel made of corn or other high-starch plants.
While ethanol is better for the environment, it is not friendly to the small engine in your SCAG lawn mower. Ethanol attracts moisture from the air and introduces it to the fuel system.
This ethanol and moisture mixture can corrode fuel components and leave behind a gummy substance that results in fuel restrictions.
In addition to these negative effects, the ethanol and water mixture will separate from gasoline over time and sink to the bottom of the tank. The engine can be damaged when this mixture runs through the engine as it burns very hot.
Always choose a gas with a minimum octane rating of 87 and a maximum ethanol content of 10%. Stay away from fuels with higher ethanol contents than this like those sold as E15, E30, or E85. Check out “This is the Type of Gas SCAG Lawn Mowers Use” for more information
Because gasoline begins to break down rather quickly, always purchase fresh gas and use it within 30 days.
If you purchased more gas than you are able to use within this timeframe, add a fuel additive to stabilize the gas so it lasts a little longer. A product like Sea Foam Motor Treatment can be added while the fuel is still fresh.
Solution: If you find the fuel in your SCAG mower is old, drain the fuel tank using a fuel siphon pump. Refill the tank with fresh fuel and a fuel additive like Sea Foam Motor Treatment to stabilize the fuel, clean the fuel system and reduce moisture.
Read more about why I choose to use Sea Foam in “Use Sea Foam Fuel Additive in a Lawn Mower to Stabilize Your Fuel“.
Plugged Air Filter
An air filter is used on a SCAG mower to protect the engine from wear and damage. When using your mower, dirt, and debris are tossed into the air causing dirty air conditions.
The filter prevents this dirt from entering the air intake and getting to the engine.
The air filter must be checked and cleaned regularly or it may become so plugged that sufficient air isn’t able to pass through the filter. This starves the engine of air and can cause it to quit running.
To avoid this, I recommend starting each mowing season off with a new air filter. Your air filter maintenance doesn’t stop there. You must check its condition and clean it several times throughout the season.
Never attempt running your SCAG mower without an air filter. Removing the filter may get your mower to start and run, however, you are taking the risk of getting small particles of dirt and debris in the engine. This can cause significant engine damage resulting in a large repair expense.
Solution: Remove and check the air filter’s condition by following these steps:
Clean a SCAG Lawn Mower Paper Air Filter Element:
- Remove the air filter cover.
- Remove the air filter. Be careful to keep dirt from falling into the air intake.
- Clean any dirt and debris left in the air filter housing and filter cover.
- Tap the filter against a solid surface to loosen and remove as much dirt as possible.
- Hold the filter up to a light source to check if you can see light shine through the filter. If you can, go ahead and reuse your air filter. If you cannot, you must purchase a new filter.
- Install the air filter and reinstall the cap on the filter housing.
Plugged Fuel Filter
The fuel filter is used to strain fuel as it comes out of the fuel tank to keep dirt out of the fuel system.
Dirt and deposits left behind by running old or dirty fuel can clog the filter resulting in an inadequate amount of fuel flowing through the filter and into the fuel lines.
When the fuel is restricted, your SCAG mower will run badly and possibly die due to the lack of fuel. I recommend replacing your fuel filter annually to reduce the likelihood the filter becomes plugged.
You may have to change it more often if you are running very dirty fuel.
Solution: If you find your SCAG fuel filter is plugged, remove the filter and install a new filter. Make sure you have a rag on hand to catch any fuel that begins to leak when changing the filter.
Take a look at the new filter and locate the arrow on the side of the housing. Make sure this arrow is pointed in the direction of the mower’s fuel flow.
Clogged Fuel Lines
The gummy deposits left behind from running old gas can cause the fuel lines to become clogged. Your SCAG will stop running when these clogs prevent sufficient gas to the engine.
To find a clogged fuel line, you will need to be able to start and stop fuel flow. Do this using the fuel shut-off valve. You can also use pinch-off pliers to crimp the fuel line to stop the flow.
Stop the fuel flow. Isolate a section of the fuel line you need to check. Remove the end of the line that is furthest from the fuel tank and place it in a container.
Make sure the container is placed lower than the fuel tank because fuel cannot run uphill without the help of the fuel pump. Start your fuel flow and watch the flow from the fuel line into the container.
If you find you have sufficient flow, shut off the fuel flow and reattach the fuel line. Continue checking additional sections of the fuel line. If you don’t find a problem in the fuel lines, keep checking the other fuel components for a restriction or failure.
Solution: When you find a section of the fuel line that isn’t allowing good fuel flow due to a clog, shut off the fuel flow and remove the fuel line from the mower.
Spray carburetor cleaner into the line to help loosen the blockage. Follow this by blowing compressed air through the line to remove it. Repeat as necessary. If you are unable to clear the blockage, replace the line with a new fuel line.
Varnish and deposits left behind by old gas can interfere with the carburetor’s function. The carburetor regulates the amount of fuel that gets mixed with air so combustion can form in the cylinder.
When the carburetor doesn’t function correctly, it can cause your SCAG mower to run sluggishly and stall.
Solution: Before you tear your carburetor apart, make sure you have confirmed you are getting fuel to the carburetor. Once that is confirmed, remove your air filter and spray carburetor cleaner into the air intake. Start your SCAG.
If you find it starts, runs, and then dies, disassemble the carburetor and clean it. Follow the steps in this guide to clean your carburetor. Read why you should avoid using starter fluid to start a mower here.
Plugged or Broken Cooling Fins
A reason why your SCAG engine will shut down is when it gets too hot. Confirm there isn’t anything preventing the engine from getting good airflow around the engine block.
This includes checking for plugged or broken cooling fins. The cooling fins push air to keep the engine block and cylinder cool.
Solution: Take caution working around your hot engine. Remove any debris stuck in the cooling fins and replace any broken fins. Remove any debris around your engine and engine shroud. Ensure your heat shield is attached securely.
Insufficient Engine Oil Level
Your mower requires a specific amount of engine oil in the crankcase for the engine to run at its best.
Most people know problems can develop when your engine oil becomes too low, but don’t know you can also have problems if there is too much oil in the crankcase.
Too Much Engine Oil
Too much engine oil in your SCAG lawn mower can cause it to shut down. Excessive oil will cause increased pressure to build in the crankcase.
When the crankshaft and rod have to push through this extra oil, the engine can overheat and die.
Remove a little engine oil through the drain plug or oil filter. You can also use an oil evacuator or turkey baster to suck oil through the engine oil fill area.
You can also remove a little oil from the oil filter or drain plug. Check the engine oil level on the dipstick. Continue to add or remove oil until the oil level is at the full line on your dipstick.
Too Little Engine Oil
You may have developed an engine oil leak or have a problem in your engine where it is using or burning oil. When you don’t have enough oil to keep the internal engine parts sufficiently lubricated, friction starts to build creating heat.
This heat can overheat your engine and cause it to die. The heat can be so hot, your internal engine parts will start to melt.
Here’s the bad news: If your engine shuts down because of a lack of engine oil, chances are significant damage was done.
Your best solution here is to take your mower to an experienced small engine mechanic to tear down your engine and perform tests to determine how much damage was done.
Solution: If correcting the engine oil levels above does not correct your engine problem, consult a small engine mechanic.
Running with an insufficient engine oil level may have resulted in engine damage like a blown gasket, burnt valve, or damaged internal parts.
Bad Spark Plug
A fouled spark plug on your SCAG can cause the plug to fire intermittently causing it to run sluggishly or die.
In addition to a fouled plug, a spark plug can cause running problems when it is not properly gapped, it is damaged, or the spark plug wire isn’t securely connected.
Solution: Clean your spark plug tip. If you find the tip of your spark plug is very dark, has a burnt electrode, or is damaged, replace your spark plug. Make sure the plug is gapped following the engine manufacturer’s specifications.
Securely attach your spark plug wires. I recommend replacing the spark plugs annually to minimize starting and running problems due to dirty or worn plugs.
Bad Ignition Coil
The winding on the ignition coil can separate and short out when your mower is hot. When this happens, the spark plugs are unable to get the voltage they need to create spark.
This can cause your mower to die after it’s been running for a while.
Solution: Identify a bad ignition coil using an ohmmeter to check for a break in continuity. Replace the ignition coil if you find there is a break.
Incorrect Choke Position
The choke reduces the amount of air the engine receives. This is used when starting a cold engine to allow more fuel and less air to form combustion in the cylinder.
Solution: The choke lever must be placed in the off position after the engine is warm to allow additional airflow or the mower will sputter and die.
Bad Gas Cap or Tank Vent
A fuel tank vent that no longer vents can restrict fuel flow and cause your SCAG mower to shut down. When the vent is plugged, the fuel tank forms a vacuum not allowing gas to flow to the engine.
Run your mower with and without the cap for periods of time to see if a clogged vent is the cause of your SCAG mower dying. First, remove or loosen the fuel cap and allow your mower starts and run.
If it runs well, reinstall the cap and allow your mower to continue to run.
When you find the mower starts to sputter and shut off after a while, you may have a clogged fuel tank vent.
Determine whether your mower has a tank vent located on the fuel tank or if the vent is located in the fuel cap. Replace the clogged vent.
Solution: Replace a plugged fuel tank vent.
Plugged Mower Deck
A mower deck that is plugged full of debris can cause your SCAG lawn mower to shut down. This is because the engine must work harder to turn the blades through a deck full of debris.
This can cause your engine to overheat and shut down.
Solution: Prevent this from happening by regularly scraping your deck to keep it clean. Avoid mowing in wet conditions as wet grass clumps and sticks to your mower deck. You can try using a deck spray to minimize grass buildup.
Deck sprays are not a miracle product that prevents all buildup, but it can minimize the amount of debris collecting under the deck.
Why is My SCAG Mower Battery Not Charging?
Make sure you are running your SCAG at a high engine speed. Don’t allow your mower to idle for long periods of time. It requires the power of the engine to charge your battery.
If you continually have to charge your battery and have confirmed the battery and wiring is in good condition and securely attached, you may have a problem with the charging system.
Solution: There are some steps you can take to check the condition of your battery and charging system which I explain in this article. If after performing these tests, you find you have a bad battery, replace your battery.
When you find the charging system isn’t working right, I highly recommend having an experienced mechanic diagnose and repair the problem.
There are so many components that can cause the charging system to fail that, unless you know the charging system, parts can be thrown at it hoping it repairs the issue.
Electrical components can get expensive and they most likely can’t be returned because they are electrical parts.
Still Experiencing Problems with Your SCAG Lawn Mower?
Own a lawn mower long enough, you’ll start running into problems with it starting, not continuing to run, smoking, leaking gas, giving a bad cut, vibrating, or another issue.
To help you save time and money, I have put together a guide to help you troubleshoot the next problem that develops on your mower.
You can find this guide at Common SCAG Lawn Mower Problems & Solutions.
If you are unsure how to perform diagnostics and repairs on your lawn mower safely, it’s best to have a professional complete the repairs.
This will help you avoid personal injury or additional damage to the mower. Your local SCAG lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.