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Briggs & Stratton Lawnmower Starting Problems: Troubleshooting with Fixes

Briggs & Stratton engines are used in multiple power-tool applications such as pressure washers, lawnmowers, and more. Briggs and Stratton engines are not only used in their own brand but also in Craftsman, Husqvarna, and Poulan lawnmowers. Despite their reliability, there is always the chance that your machine will not start.

Briggs & Stratton lawnmower starting problems:

If a Briggs & Stratton lawnmower doesn’t start, the problem mainly lies with the fuel system components, such as choked filters, clogged carburetors, and blocked fuel tank vents. Also, issues with the ignition coil and a bad spark plug with damaged electrodes can affect the spark quality, resulting in the engine starting/stalling. If you notice the engine misfiring while running, you should check for a missing flywheel key and a faulty ignition coil.

In this article, I will give a detailed step-by-step approach to troubleshooting and fixing multiple engine/starting problems.

Briggs & Stratton Riding lawnmowers

Riding lawnmowers are designed for operation on rough terrains and fields with large acres to provide ruggedness and improve productivity.

Briggs & Stratton uses its E, EX, EXI, and PXI series four-stroke engines for riding lawnmowers. Let’s troubleshoot some of the common problems in riding lawnmowers:

1. Briggs & Stratton Lawnmower does not start?

If the lawnmower doesn’t start, start by checking the fuel level and the fuel tank vents for clogging. Examine and clean the air filter and the carburetor. Also, replace the spark plug if needed.

Here are the steps that you can follow to troubleshoot this issue:

1. Fuel Tank:

The first thing you should check is the fuel level in the tank. If the fuel quality has degraded after a prolonged storage period, I recommend that you drain this fuel in a separate tank and add fresh fuel instead to improve the engine’s performance. If the fuel level is adequate, check the tank cap.

Fuel tank caps have vents to allow vapors to escape. If these vents are blocked, vapor pressure builds up, which reduces the fuel flow rate to the carburetor, thus reducing the power output from the engine. If the vents are blocked, use a metal wire to clean them from dust and avoid vapor locks.

If the problem is not solved, move to step 2.

2. Filters and Carburetors:

The air filter separates dust and foreign particles from the air and often needs to be cleaned to allow uninterrupted airflow to the carburetor. You should ensure that the air filter is checked and cleaned after every 25 hours of operation. When the filters are clogged with dust, the engine may not start or stall.

The carburetor is where the fuel and air mix optimally to initiate combustion in the engine. These carburetor jets could get blocked over time due to residual fuel that decomposes into sticky white deposits. As a result, the engine could undergo starting problems.

To clean the carburetor, you can follow the steps below:

  • Remove the carburetor: Locate and access the carburetor on your engine by first removing the air filter assembly. Remove the mounting screws and the governor link of the carburetor. Detach the fuel lines from the tank and to the engine, and the carburetor is removed entirely from the engine.
  • Disassemble and clean: After removing, detach the bowl nut and the bowl itself from the carburetor and drain any leftover fuel. Using a carburetor cleaner liquid or WD-40, spray the fuel jets inside the carburetor to remove any solid deposits. Make sure all the jets are clean and free of debris. After cleaning, reassemble the carburetor and attach it back to the mower.

I recommend buying a carburetor repair kit that contains all the necessary supplies for the maintenance and repair of carburetors.

If the issue remains, examine the spark plugs.

3. Spark Plugs:

The spark plug ignites the fuel-air mixture in the engine. Over time, the electrodes of a spark plug accumulate carbon and soot that diminishes spark quality and degrades the electrodes. Inspect the electrodes by removing the spark plug using a socket wrench.

If they are dirty, clean them with a metal brush. Check that the gap with a feeler gauge, and adjust if needed. If the spark plug is damaged or difficult to clean, I recommend replacing it.

2. Briggs & Stratton Lawnmower starts but then dies?

If a lawnmower stalls repeatedly, it’s usually due to a gummed-up carburetor or damaged air and fuel filters.

The lawnmower engine receives an air-fuel mixture to produce power. The engine usually runs at an optimal air-fuel proportion (usually 12). When the mixture becomes lean (>12) or rich (<12), the engine’s power drops, and it tends to stall. Let’s troubleshoot the possible reasons:

  • Bad filters: When the air and fuel filters are clogged or damaged, the air-fuel mixture gets affected, and the engine slows down. Hence, inspect the filters on your lawnmower. A foam air filter can be cleaned. A damaged foam or paper air filter should be replaced. If the fuel filter is dirty, try to clean it. Else replace it.
  • Clogged Carburetor: Cleaning the carburetor from stale fuel deposits usually resolves stalling problems in small engines. Ensure you clean the carburetor as per the instructions in the above section.
  • Vapor Lock: A vapor lock due to clogged fuel tank vents could also be causing this problem. Turn your engine off and open the fuel cap to release the vapors. Now, the engine would restart and run without stalling. If this is the case, ensure the fuel tank cap vents are clean.

3. Briggs & Stratton Lawnmower is smoking?

A lawnmower usually smokes if the oil and fuel in the engine are burning. In some cases, a clogged air filter could also produce this problem.

Notice the color of the smoke produced by the exhaust.

– White Smoke:

If the smoke color is white or bluish-white, it is due to engine oil getting burnt with fuel. It is probably because you overfilled the crankcase with oil, and now it seeps into the combustion chamber. A low-grade oil (with too low viscosity) may also cause this problem.

Also, whenever you tilt the mower, tilt it with the carburetor facing upwards so that the crankcase oil doesn’t enter the combustion chamber.

– Black Smoke:

If the smoke is of dark color, it is due to unburnt fuel leaving the exhaust. The black color is due to hydrocarbons that aren’t burnt in the fuel. This is because your engine isn’t receiving enough air to burn the fuel completely. Check the air filter. Clean or replace if needed. I recommend checking the air filter regularly.

4. Briggs & Stratton Lawnmower Runs Rough/misfires?

A lawnmower engine could be misfiring due to a broken or missing flywheel key. A worn-out spark plug could also be the cause of the problem.

The flywheel is a metal part that minimizes the crankshaft’s jerks and provides a smooth rotational motion to the transmission pulley. The flywheel aligns itself with the crankshaft via a flywheel key in the slot.

When the mower blades hit a hard object, the key gets sheared off, and the lawnmower may run jerky. In some cases, it may not run at all. To fix this, the flywheel key needs to be changed.

  • Step 1. Disassembly: Make sure you remove the spark plug wire before this repair. Remove the blower housing and access the flywheel.
  • Step 2. Remove the flywheel nut: Using a socket wrench, loosen the flywheel nut and remove the flywheel cup on top. You could also use a puller tool to remove the nut completely. While loosening the nut, keep a metal block between the blades to prevent the crankshaft from rotating.
  • Step 3. Change the key: After the nut is detached, remove the remnants of the broken key and install a new key in the slot. Reattach and tighten the flywheel nut while keeping the blades fixed. After replacing the key, check your lawnmower and see how it performs.

Sometimes, a damaged spark plug with faulty electrodes also causes engine misfiring. Check the spark plug, clean it if needed, and replace it when damaged. Sometimes, the spark plug may look fine but is still faulty.

You can use a spark plug tester to check if it is ok. If you are not entirely convinced, replace it and check if it makes a difference.

5. Briggs & Stratton Lawnmower has a dead battery.

If your lawnmower battery is dead, you can jumpstart it by connecting it to your car’s battery. Check if the cables are correctly attached to the battery. Clean if needed.

If the lawnmower doesn’t start, one of the reasons is a dead battery. To fix this problem, you can connect the terminals of your car battery via a jumper cable to the lawnmower battery. Connect the red (+) and black (-) wires with their respective signs at the other battery.

Restart the mower again and run the engine idle for a few minutes. This will slowly recharge the battery and won’t cause problems again.

To prevent this from happening repeatedly, follow the steps below:

  • Bad Battery: If your lawnmower starts after jumpstarting, the battery may be in bad condition. You can use a battery tester for this. If your battery is dead quickly after completely recharging, it is also a sign that it needs replacing.
  • Clean the terminals: Ensure the battery terminals are clean and do not have white silt deposits. You can use a metal brush to clean the terminals.
  • Check electrolyte level: Regularly check the water level if your mower uses an older battery type. Ensure it stays at the recommended level. If the battery continues to die, get its pH value tested by a professional. If the pH has increased, it must be refilled with an acid solution.

Briggs & Stratton Self-Propelled lawnmowers

Self-propelled lawnmowers are relatively cheaper, are easier to maneuver and maintain, and are suitable for regular-sized lawns. In self-propelled lawnmowers, Briggs & Stratton uses the E, EX, EXI, and PXI engine series.

Troubleshooting these lawnmowers involves almost the same methods as discussed for riding lawnmowers. The problems encountered in these machines are the same, except that they come with a pull cord.

1. Briggs & Stratton Lawnmower engine doesn’t start?

You should check for insufficient fuel in the tank, worn-out spark plug, clogged air filter, and carburetor plugged with deposits, as that could prevent the engine from starting.

Please ensure that all the filters (air and fuel) are clean and in working condition. Check for clogged fuel jets in the carburetor and use a WD-40 spray to clean them properly. Apart from the servicing, refill the tank with fresh fuel and add a fuel stabilizer to prevent it from decomposing if you expect the gas to stay in the tank for more than a month or two.

2. Briggs & Stratton Lawnmower pull cord doesn’t work?

If the pull cord gets stuck or becomes free, it is due to damaged components in the recoil assembly.

To fix this problem, the recoil assembly needs to be examined. You can follow the step-by-step procedure to perform this repair.

  • Step 1. Disassembly: First, disconnect the spark plug wire of your mower to prevent the engine from accidentally starting up. Remove the blower housing and access the recoil assembly.
  • Step 2. Inspect the components: The recoil assembly uses a torsion spring to wind and unwind the starter pulley and the pull cord. If the spring gets damaged, the pulley won’t unwind, and the rope gets either stuck or loose. Apart from the spring, check the bearing of the pulley and make sure the pulley rotates freely.
  • Step 3. Perform replacements: After identifying the faulty components, replace them with identical parts. If necessary, you could also ask a professional to help replace these parts after you’ve performed the initial inspection yourself.

Lawnmower Starting Problems

1. Gas-Powered Lawnmower Starting Problems

S#
Problem
Causes
Fixes
1
Lawnmower doesn’t start
a. Empty fuel tank
b. Clogged carburetor
c. Air filter blocked with dirt.
d. Spark plug with worn-out electrodes
a. Before adding fresh, drain old fuel residues from the tank.
b. Inspect and clean the air and fuel filters from debris. Replace if necessary.
c. Disassemble and clean the carburetor using a carb. cleaner liquid.
d. Replace the spark plug if electrodes are worn out.
2
Lawnmower starts but then dies
a. Blocked air filter
b. Clogged carburetor jets
c. Vapor lock in the fuel tank
a. Clean the air filter using soap and water. Replace if needed.
b. Clean the carburetor jets from residues using a carb cleaner spray.
c. Clean the fuel tank vents to prevent a vapor lock.
3
Lawnmower is smoking
a. Oil leaking into the combustion chamber
b. Blocked air filter  
a. Avoid overfilling the oil tank.
b. Always tilt the mower with the air filter pointing upwards.
c. Check and replace worn-out gaskets.
d. Clean the air filter.
4
The lawnmower runs rough/misfires
a. Stale fuel deposits in the fuel system.
b. Broken flywheel key
a. Perform a complete tune-up involving cleaning the filters, carburetor, and fuel lines.
b. Replace the flywheel key.

2. Corded Electric Lawnmower Starting Problems

S#
Problem
Causes
Fixes
1
Lawnmower doesn’t start
a. Loose connection
b. Defective extension cord
c. Faulty start switch
d. Tripped circuit breaker
a. Ensure the connections aren’t loose and the socket is working.
b. Try plugging in directly without an extension cord.
c. Test the start switch using a multimeter and replace it if needed.
d. Reset the tripped circuit breaker.
2
The lawnmower shuts down during operation.
a. Loose plug at the socket
b. Tripped circuit breaker
c. Motor winding damage
a. Ensure the connection isn’t loose and the socket works.
b. Reset the circuit breaker or replace the blown switches.
c. Contact customer support to seek a replacement in case of motor damage.

3. Cordless Battery Powered Lawnmower Starting Problems

S#
Problem
Causes
Fixes
1
Lawnmower doesn’t start
a. Low battery
b. Faulty start switch  
a. Ensure the battery is fully charged.
b. Test the start switch for continuity using a multimeter.  
2
The lawnmower shuts down during operation.
a. Low battery
b. Overheating
c. Debris obstructing the blades  
a. Ensure the battery is fully charged.
b. Let the lawnmower cool down for 10-15 minutes and restart.
c. Clean the mower’s underside and remove any debris/grass clippings.

4. Robotic Lawnmower Starting Problems

S#
Problem
Causes
Fixes
1
Lawnmower doesn’t start
a. Disconnected boundary wire
b. Faulty power supply
c. Software update
d. Debris stuck in blades
a. Ensure the boundary wire is connected to the charging station.
b. The battery connections should be correct and the charging should be sufficient.
c. Keep the software up to date.
d. Remove any debris stuck between blades.
2
The lawnmower keeps shutting down mid-operation
a. Ensure the boundary wire is connected to the charging station.
b. The battery connections should be correct, and the charging should be sufficient.
c. Keep the software up to date.
d. Remove any debris stuck between blades.
a. Avoid mowing when the conditions are damp.
b. Resolve error messages on the display.
    ..