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17 Reason Your MTD Lawn Mower Won’t Start

Nothing is more frustrating than a lawn mower that won’t start when you’re trying to get your mowing tasks done. You finally find time in your busy schedule to tackle the lawn, but now you’re going to end up spending the day trying to fix it. Here’s a guide with the most common starting issues to help you locate the cause of your MTD starting problem.

An MTD lawn mower won’t start when there is bad fuel; a plugged air or fuel filter; a clogged fuel line; dirty carburetor; a bad spark plug, ignition coil, starter solenoid, ignition switch or safety switch; or a bad battery or charging system.

Follow all safety precautions listed in the owner’s manual for your MTD lawn mower to avoid injury.

Lawn mower engine

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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing or operating. Consult a professional if you don’t have the skills, knowledge or are not in the condition to perform the repair safely.

This is Why Your MTD Lawn Mower Won’t Start

No Gas in Your MTD Gas Tank 

I’m sure you know gas is required for a gas-powered lawn mower to start and run. I mention it only to serve as a reminder in case you skip this obvious item out of frustration.

Solution: Fill your gas-powered MTD mower with fresh gasoline with an octane rating of 87 or higher. Choose the right kind of gas with an ethanol level no greater than 10%.  

Bad or Old Fuel in Your MTD Lawn Mower

Gas that has been sitting in the fuel tank over the off-season or for long periods of time can cause fuel restrictions, fuel component degradation and corrosion of the fuel system. Gasoline can begin to become less effective and breakdown as soon as 30 days after purchase.

Most gasolines include ethanol, an environmentally-friendly alternative fuel. While ethanol is okay to run in most vehicles, it can be harmful to the small engine ran in an MTD mower. Ethanol attracts moisture to the fuel that leave behind gummy deposits and is corrosive to the the fuel system.

This ethanol and water mixture will also separate from the gasoline over time which can potentially damage the engine. This is why you must not run any fuels through your lawn mower that include more than a 10% ethanol content. The less ethanol in your fuel, the better for the engine.

MTD lawn mowers require an unleaded gasoline with a minimum octane rating of 87 and a maximum ethanol content of 10%. Straight gas is used in a 4-stage engine, while a gas and oil mix is used in a 2-cycle engine. If you are unsure of the type of engine your MTD uses, refer to your operator’s manual.

  • 4-stage (4-cycle) MTD engine:
    A 4-stage engine will have a separate fill ports, one for engine oil and one for gasoline. Fill the fuel tank with fresh unleaded gasoline.
  • 2-cycle MTD engine:
    Some MTD lawn mowers will use a 2-cycle engine. This type of engine will have one fill port for a gas and oil mix. MTD lawn mowers with 2-cycle engines require a gas to oil mix of 40:1 for mowers manufactured after 2002. Prior to this year, use a gas to oil mix of 32:1.

    Never use straight gas through a 2-cycle engine as this will damage the engine and certainly ruin your engine. Use a good 2-cycle engine oil mixed with gasoline. 2-cycle engine oil is different than engine oil.

Solution: Remove the old fuel using a fuel siphon and add fresh fuel. Add a fuel additive like Sea Foam Motor Treatment to stabilize the gas, clean the fuel system and reduce moisture. Read more about why I use Sea Foam in my lawn mower here.

Faulty MTD Mower Gas Cap 

Your gas cap is design with a vent to allow air to pass through the cap. When this vent gets plugged, a vacuum will form in the fuel tank preventing fuel from leaving the tank and getting to the engine. 

You can identify a fuel tank cap problem by running your mower with and without the cap. If it starts and runs without the fuel cap, but dies after you let your mower run with the fuel cap on for a while, you most likely have a cap problem. Be careful to not allow dirt or debris to enter the fuel tank.

Solution: Replace with a new fuel cap. You can find one on Amazon or visit your local MTD dealership. 

Bad Spark Plug or Loose Connection in Your MTD Lawn Mower

Your MTD will not run with a bad spark plug, loose wire or insufficient gap. A spark plug that is dirty with carbon buildup, has become damaged or has a burnt electrode must be replaced. Any of these items can cause the spark plug to fail and cause your engine to not start.

Solution: Remove the spark plug and inspect it for signs of carbon buildup or damage. You can attempt to clean a dirty spark plug with a wire brush. I prefer to replace the inexpensive part because a spark plug is maintenance item required to start and run your MTD mower well. A bad plug can cause the mower to misfire and run sluggish.

Make sure the spark plug is gapped according to the engine manufacturer’s specification. Install the spark plug and securely attach the spark plug wire.

Plugged Air Filter on Your MTD Lawn Mower

A plugged air filter can keep the engine from getting clean air. It can starve the engine causing the mower not to start. Keeping the air filter clean and free of dirt and debris collecting on the filter can prevent significant engine issues including overheating.

Replacing your air filter annually and cleaning it several times during the lawn mowing season will help protect your engine and allow it to run at its best.

Solution: Remove your air filter and inspect it. Clean the filter or replace it if necessary using the following steps:

Clean an MTD paper air filter:

  • Remove the air filter housing cover.
  • Remove the air filter being careful not to allow dirt to fall into the air intake.
  • Wipe out any dirt that remains in the housing.
  • Tap the plastic or rubber part of the filter against a hard surface to loosen the dirt so it falls out of the filter.
  • Once you have removed as much dirt as possible, hold the filter up to a light source. If you can see light through the paper filter, reuse the filter. If you can’t see light or if it is covered in oil, replace the air filter.
  • Install either a clean reusable filter or a new filter.
  • Reattach the air filter cover.

Clean an MTD foam air filter:

  • Remove the air filter housing cover.
  • Remove the air filter being careful not to allow dirt to fall into the air intake.
  • Wipe out any dirt that remains in the housing.
  • Reuse the filter if it is in good condition and not brittle, forming dark spots or have tears in the filter. Purchase a new foam air filter if you find any of these conditions.
  • Wash a filter that is able to be reused. Use a mild dish soap and water to remove dirt. Rinse until clear.
  • Lay flat to dry.
  • Once completely dry, coat with a foam filter oil and replace in the filter housing.
  • Reattach the cover.

Bad Fuel Pump on Your MTD Lawn Mower

The fuel pump exists to pump fuel to the carburetor. Your MTD mower will have a fuel pump when the fuel tank sits below the carburetor and a pump is require to move the fuel uphill through the fuel line. A fuel pump, just like any other mechanical part, can fail over time. A likely cause is due to old fuel deteriorating the pump components.

Solution: To identify a failing fuel pump, first, inspect your vacuum fuel pump for cracks. If you see fuel outside of the fuel pump or cracks in pump, the pump will no longer being able to create the pressure needed to pump fuel. 

Using the fuel shut-off valve, if your mower has a valve, or pinch pliers to stop and start fuel flow will help you control fuel flow. Stop and start flow to make sure you are getting fuel to the pump.

Once you verify your pump is getting fuel, check to make sure that fuel is being pumped out of the pump in a steady or pulsating flow to identify whether or not your fuel pump is bad.

Plugged Fuel Filter on Your MTD Lawn Mower

Your fuel filter is a line of defense to prevent dirt and debris into the engine by straining the fuel. The filter is designed to strain the fuel keep dirt out of the fuel system. When the filter isn’t changed regularly or the fuel is extremely dirty, the filter will become plugged keeping fuel from passing through the filter.

Solution: If you are not getting fuel flowing through the fuel filter, replace the filter. You will find an arrow on the new filter that must be installed with the arrow pointing in the direction of the fuel flow.

Clogged Fuel Line on Your MTD Lawn Mower

Old fuel and dirt leave deposits that can clog your MTD mower’s fuel line.  

Solution: Remove the fuel line, spray carb cleaner into the tube and use compressed air to blow air through the tube until the line is free of dirt and gummy residue. You can also replace with new fuel line

Clogged & Dirty Carburetor on Your MTD Lawn Mower

The function of the carburetor is to regulate the right amount of gas with the right amount of air so your engine can create a combustion allowing the mower to start and run. Carburetors can get crusty buildup and gummy deposits from using old fuel containing ethanol.

When the carburetor is no longer to regulate the fuel your engine receives, your MTD engine will run rough or it may not even start at all.

Solution: If you are somewhat mechanical, you can try to clean the carburetor yourself, otherwise bring it to your lawn mower repair shop. You can find steps for cleaning your carburetor in this article

You may choose to replace the carburetor if it appears to be in very bad condition. 

Bad Battery or Loose Terminals on Your MTD Lawn Mower

Your MTD lawn mower requires a charged battery in order to start. If your cables happen to be loose or your battery terminals show signs of corrosion, they can cause your mower staring problems.

Solution: Test your battery with a multimeter. You will want a reading at about 12.7 volts. Charge your battery if it is lower than this level. You can find more information on charging your battery here. If your battery does not hold a charge, you will need to replace it with a new battery. 

Bad Safety Switch on Your MTD Lawn Mower

Your lawn mower may use several safety switches in its operator’s presence control system. The switches are designed to kill the engine when the operator leaves the seat. A faulty switch may not recognize when the operator is in or out of the seat causing your mower not to start. 

Solution: You can temporarily bypass the safety switch to identify a bad switch. Do not operate a mower without the safety switch installed for your safety. Always have safety switches installed and working on your equipment. Replace a bad switch. 

Bad Ignition Switch on Your MTD Lawn Mower

You insert the key into your ignition switch and turn it only to find nothing happens. Your MTD mower does not start. The ignition switch can be the culprit. You can use a multimeter to test the ignition switch 

Solution: Replace the switch if bad 

Faulty Ignition Coil on Your MTD Lawn Mower

The ignition coil provides voltage to the spark plug so it can fire and start the engine. The engine will not start if the spark plug isn’t able to fire.  

Solution: After you verified your spark plug is in good condition, check the continuity of your ignition coil using an ohm meter. Replace the ignition coil if you find a break in the continuity. 

Bad Starter Solenoid on Your MTD Lawn Mower

A lawn mower 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 MTD mower solenoid may be bad is when a wire attached to your solenoid gets hot and begins to smoke or melt.

Solution: Test your MTD mower solenoid by following the steps here. Replace your solenoid if it is found to be bad.

Faulty Charging System on Your MTD Lawn Mower

If your mower runs with a battery, the charging system can drain the battery and not keep it charged causing your MTD to not start. 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 ohm meter. 

Solution: If you believe the problem to be in your charging system, I suggest you allow a small engine mechanic to identify which part of the charging system is your problem. Taking a guess at the problem and throwing parts at your mower can get pretty expensive.

Bad Starter Recoil on an MTD Mower 

If you own an MTD push mower without electric start, you will have a recoil to start the engine. The recoil can fail so you are unable to start your mower. A bad pulley; loose or missing spring; or broken clips can keep your recoil from working.

Solution: You can attempt to replace the spring and restring the recoil. If it does not work because other components in your recoil are damaged, such as the clips or the pulley, you are better off just replacing the recoil assembly.

Incorrect Operating Procedure to Start Your MTD Lawn Mower

A MTD mower has safety features that won’t allow your mower to start unless you follow their starting procedures which includes setting your parking brake.

Make sure the choke setting is correct. The choke restricts airflow allowing more fuel into the cylinder to start a cold engine. You must adjust the choke so it doesn’t continue to restrict airflow once the engine is warm or it will shut down.

Solution: Refer to your MTD operating manual to ensure you are operating your lawn mower correctly so you don’t set off the safety features that won’t allow it to start.