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17 Reasons a Briggs & Stratton Lawn Mower Won’t Start: FIX

You will find Briggs & Stratton small engines used on many different brand mowers including select Toro, Craftsman, Yards Machines, and Cub Cadet lawn mowers.

When your mower begins to act up and no longer starts, you’ll need to figure out why the engine is no longer getting sufficient air, fuel, and spark.

A Briggs & Stratton lawn mower engine won’t start due to a bad spark plug, plugged air filter, wrong choke setting, dirty carburetor, plugged fuel filter, clogged fuel line, bad safety switch, or old gas.

Briggs & Stratton riding mowers or push mowers with an electric start may have a weak battery, corroded or loosed cables, or a bad ignition switch.

Follow safety precautions including removing the spark plug boot(s) before completing any repairs.

Push mower won't start

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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.

Briggs & Stratton Lawn Mower Starting Problems

1. No Gas

Obviously, if you run out of gas your Briggs and Stratton mower will not start. I only mention it here just in case you skipped over checking the fuel level when you began troubleshooting your starting problem.

You may have a faulty fuel gauge or you may have developed a fuel leak and are going through more fuel than normal.

SOLUTION: Fill and empty the tank with fresh unleaded gasoline with a minimum of 87-octane. Choose a gas with an ethanol level no greater than 10%.

Briggs & Stratton lawn mowers sold today use 4-cycle engines that require straight gasoline.

If you are using older mowers with Briggs & Stratton engines, you may have a 2-cycle engine that requires a gas and oil mixture. A 2-cycle engine will only have one fill port for a gas and oil fuel mix.

2. Bad or Old Fuel

Gas begins to deteriorate, break down, and become less effective after about 30 days. The ethanol used in gasoline attracts moisture.

This moisture, once it evaporates, leaves a gummy residue behind that can clog your fuel system including your fuel lines, filter, and carburetor. 

It is necessary to purchase fuel from a busy gas station and use it within a 30-day time period.

If you are unable to consume the fuel within this time, you need to add a fuel additive to stabilize the fuel so it lasts a little longer without breaking down. Read more about the advantages of Sea Foam here.

SOLUTION: Remove the old fuel from the fuel tank using a fuel siphon pump. Add fresh fuel along with a fuel additive to clean and remove moisture from the fuel system.

I prefer to use the product Sea Foam Motor Treatment. STA-BIL is also a good product.

Once you are able to get the mower started, start and allow the engine to run for a while to allow the treated fuel mixture to work its way through the fuel system.

3. Bad Fuel Cap

Your fuel cap has a vent. When this vent gets plugged, your fuel tank will create a vacuum preventing your Briggs & Stratton mower from getting gas to the carburetor

To check whether your gas cap is the cause of your starting problem, remove the cap and start your mower. If the Briggs & Stratton that wouldn’t start now starts, go ahead and reinstall the cap with the lawn mower still running.

What you’re waiting for now is for the mower to sputter and die from a lack of fuel. If it does, remove the cap and see if the mower will start up again.

You have a problem with the fuel cap when you experience this kind of starting and dying from a fuel cap that is removed and installed on your Briggs & Stratton.

SOLUTION: Replace with a new fuel cap. You can find one on Amazon or visit your local Briggs & Stratton dealership. 

4. Bad Spark Plug or Loose Connection

Another reason your Briggs & Stratton won’t run may be due to a bad spark plug connection or a damaged spark plug. A plug that has carbon buildup or oil on the tip can foul out causing your engine to misfire and not start.

Check the spark plug wire to ensure it’s making a good connection. Your spark plug must be gapped to the engine manufacturer’s specification.

You can experience starting and running problems with a loose spark plug wire or an incorrectly gapped spark plug.  

SOLUTION: Remove your spark plug and inspect it for signs of carbon buildup, cracked porcelain, or burnt electrodes. Replace with a new spark plug(s). Make sure the spark plug is gapped correctly using a feeler gauge.

5. Bad Ignition Coil

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. Replace the ignition coil if you find a break in the continuity. 

6. Plugged Air Filter

The engine in your Briggs & Stratton requires air to run. If your air filter gets extremely dirty, it can starve the engine of air because air will no longer be able to pass through the filter. A Briggs & Stratton engine that doesn’t get sufficient air will not start.

When the airflow is blocked by your air filter the engine must find air to continue to run. It may begin to overheat and draw what air it can find from the crankcase which can cause extensive damage to the engine.

SOLUTION: Clean a dirty air filter. Replace a filter that is extremely dirty or damaged. Follow the instructions below to clean most types of Briggs & Stratton air filters.

If you are unsure of the type of filter you have and its cleaning procedures, refer to your operator’s manual.

Clean a Briggs & Stratton PAPER air filter:

  • Remove the air filter cover.
  • Remove the air filter.
  • Remove loose dirt in the air filter housing and from the air filter cover using a clean dry cloth. Be careful and don’t allow dirt to fall into the air intake.
  • Tap the air filter element against a solid surface to loosen dirt so it falls out of the filter.
  • Hold the filter up to a light source. If you can see good light through the paper, go ahead and continue to use the filter. If you can’t see good light or the filter is damaged, the filter needs to be replaced with a new one.
  • Install the new or clean air filter.
  • Reattach the air filter cover.

Clean a Briggs & Stratton FOAM air filter:

  • Remove the air filter cover.
  • Remove the air filter.
  • Remove loose dirt in the air filter housing and from the air filter cover using a clean dry cloth. Be careful and don’t allow dirt to fall into the air intake.
  • Inspect the air filter for damage. If it is very dark in color, brittle, or has tears in it, it’s time to replace it with a new one. If it is in good condition, continue cleaning the filter.
  • Wash the foam filter in water and mild detergent to remove oil and dirt.
  • Rinse the filter until it runs clear. Squeeze the filter to remove water. Don’t wring the filter as this can tear it.
  • Allow the filter to dry.
  • Apply clean engine oil to the filter so it is completely covered. Squeeze excess oil from the filter. (NEVER APPLY OIL to a foam pre-filter. A pre-filter is a filter that wraps around a paper filter element. This can damage the paper filter).
  • Install the filter.
  • Reattach the air filter cover.

7. Bad Fuel Pump

The fuel pump exists to get fuel to the carburetor. You’ll only find a fuel pump used with a Briggs and Stratton engine when the carburetor sits higher than the fuel tank. You most likely won’t find one on a small push mower.

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.

SOLUTIONTo 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 the pump, the pump will no longer be able to use the pressure off the crankcase to move fuel to the carburetor. 

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

If you are not getting good flow to the pump, check the fuel line or fuel filter for restrictions.

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.

Do this by stopping your fuel flow and removing the fuel line from the carburetor. Place the line in a container. Start your fuel flow and your mower.

Watch the flow of fuel into the container. If you have a good consistent or pulsating flow of fuel, your fuel pump is okay. If not, replace the fuel pump.

8. Clogged Fuel Filter

Your fuel filter is a line of defense to prevent dirt and debris into the engine by straining the fuel. Make sure the fuel that is running into the filter is also running out of the filter.

If it does not, you must replace it because it is most likely plugged preventing your Briggs & Stratton from starting.

Check these places for a fuel filter:

  • Inline filter is inserted between the fuel lines.
  • A small narrow filter is inserted at the bottom of the fuel tank.

SOLUTION: Replace the fuel filter if you have found your fuel flow stops at the fuel filter. Install a new fuel filter on your Briggs & Stratton if needed. The filter must be installed so the arrow on the filter is pointed in the direction of the fuel flow.

9. Clogged Fuel Line

Old fuel and dirt leave deposits that can clog your Briggs & Stratton mower’s fuel line.  

SOLUTION: Remove the fuel line, spray carburetor 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 it with a new fuel line. 

10. Clogged & Dirty Carburetor

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

When the carburetor is no longer able to regulate the amount of fuel and air your engine receives, your Briggs & Stratton 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 Briggs & Stratton carburetor in this article

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

11. Bad Safety Switch

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 on a riding mower.

On a push mower, the mower will fail to start when the safety bail control bar isn’t brought into the handle indicating the user is present.

A faulty switch may cause your Briggs & Stratton mower not to start. Another safety switch to check is the brake switch on a riding mower.

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. 

12. Loose or Corroded Cables, Wiring, and Terminals

On riding mowers and push mowers using an electric start, check the terminals and cables for corrosion. Then look for loose cables and wiring that may cause a break in continuity.

Follow the cable off the positive battery terminal to the solenoid and the cable from the solenoid to the starter. When these cables are not tight or have corrosion buildup, your mower may not start.

Continue to check all wiring and components on your Briggs & Stratton mower.

SOLUTION: Tighten the cables and make sure all wiring is securely attached to the mower components. Use a water and baking soda mixture to remove corrosion.

Make sure you remove the negative battery cable first followed by the positive cable.

13. Weak or Bad Battery

Your Briggs & Stratton lawn mower requires a charged battery to start. If the battery is weak, you must charge it to start.

SOLUTIONTest your battery with a multimeter. You need a reading of about 12.7 volts for a 12-volt lawn mower battery. Charge your battery if it is lower than this level. You can find more information on charging a Briggs & Stratton battery and why it keeps dying here.

If your battery does not hold a charge, you will need to replace it with a new battery. 

14. Bad Ignition Switch

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

SOLUTIONReplace the switch if bad.

15. Bad Starter Solenoid

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

SOLUTION: Test your Briggs & Stratton mower solenoid by following the steps here. Replace your solenoid if it is found to be bad.

16. Faulty Charging System

While the charging system isn’t the main reason a Briggs & Stratton mower won’t start, it can contribute to a weak battery on a riding Briggs & Stratton mower that prevents the mower from starting.

When the charging system fails to charge the battery, the battery may not be able to start the mower the next time you go to use it.

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 ohmmeter. 

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.

17. Incorrect Operating Procedure

Briggs & Stratton has safety features that won’t allow your mower to start unless you follow their starting procedures.

SOLUTION: Refer to your Briggs & Stratton operating manual to ensure you are operating your lawn mower correctly, so you don’t set off the safety features that shut off your lawn mower or don’t allow it to start.

For example, on a Briggs & Stratton riding mower, the brake must be engaged and the PTO switch must be off for the engine to start.