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Lawn Mower Won't Start

The lawn mower small engine often has a separate model number. Use the small engine model number for a complete list of symptoms and parts. Watch our model # lookup video for help finding the model number.

The 18 most common part(s) or condition(s) which cause the symptom Lawn mower won't start are listed below starting with the most likely. Check or test each item and watch any available videos.


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To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Spark Plug

If the lawn mower engine does not start the spark plug might be defective. All small engines have an ignition coil. The coil is the device that provides spark for the spark plug(s). If the coil is bad power won't get to the spark plug(s). The coil is essentially a small, induction generator. It is mounted next to the flywheel. The flywheel has one or more strong, embedded magnets. As the flywheel spins, the magnet(s) zip past the induction coil, this action of a magnet passing past a coil induces a voltage. Depending on the design of the coil and the strength of the magnets, a stronger or weaker spark can be created and delivered to the spark plug(s). Each time the flywheel spins around a spark is generated. The best way to test a spark plug is to use a spark plug tester. The spark plug should have a strong, visible spark between the electrodes when the engine is cranking. If it doesn't, replace it.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Carburetor

If the lawn mower does not start, the carburetor might be clogged or have bad fuel in the float bowl. If old fuel was left in the lawn mower for a long time some of the volatile ingredients may have evaporated, leaving a thicker, stickier product that is more like varnish or shellac. This sticky fuel can clog up the small jets and ports in the carburetor and it can be difficult to burn making it hard to start the engine. The only solution is to drain the old fuel from the float bowl and thoroughly clean the carburetor with carburetor cleaner. If that isn't effective, the entire carburetor may need to be replaced.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Carburetor Kit

If the lawn mower engine does not start it may not be getting fuel. Every engine needs air, fuel and spark. The carburetor has two inputs, fuel from the gas tank and air through the air filter. The carburetor is designed to mix the air and fuel in a consistent ratio so that the engine can run continuously. If the carburetor is not getting enough air or fuel, or if the fuel is blocked inside the carburetor the engine does not start. It can be rebuilt with this carburetor kit.

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What is a model number, and where do I find it?

Other Causes and Conditions

Old or Bad Gasoline

If the lawn mower does not start, the carburetor might be clogged or have old or bad fuel in the float bowl. If old or bad fuel was left in the lawn mower for a long time some of the volatile ingredients may have evaporated, leaving a thicker, stickier product that is more like varnish or shellac. This sticky fuel can clog up the small jets and ports in the carburetor and it can be difficult to burn making it hard to start the engine. The only solution is to drain the old fuel from the float bowl and thoroughly clean the carburetor with carburetor cleaner. If that isn't effective, replace the entire carburetor.

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Start Switch

If the lawn mower engine won't start the start switch might be defective. Test the switch for continuity with an Ohm meter. If the switch is difficult to turn or works intermittently it should be replaced.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Fuel Pump Kit

If the lawn mower does not start the fuel pump might not be working properly. The fuel pump has three ports, gas in, gas out, and the pulse port. The pulse port is connected to the engine crankcase by a small rubber tube, as the engine runs air inside the crankcase alternately pressurizes and depressurizes the air in the tube which moves a diaphragm inside the pump and pumps the gas. The fuel pump also has two small check valves on the input and output ports to prevent fuel from going back to the gas tank. If the engine oil is overfilled, oil can get into the pulse port line, preventing it from working properly. Also, either of the check valves and the mechanical diaphragm inside the pump can fail. If the pump is not working properly it will have to be replaced, it's not possible to repair it. Be certain to replace all parts in this fuel pump kit.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Fuel Pump

If the lawn mower engine does not start the fuel pump might not be working properly. The fuel pump has three ports, gas in, gas out, and the pulse port. The pulse port is connected to the engine crankcase by a small rubber tube, as the engine runs air inside the crankcase alternately pressurizes and depressurizes the air in the tube which moves a diaphragm inside the pump and pumps the gas. The fuel pump also has two small check valves on the input and output ports to prevent fuel from going back to the gas tank. If the engine oil is overfilled, oil can get into the pulse port line, preventing it from working properly. Also, either of the check valves and the mechanical diaphragm inside the pump can fail. If the pump is not working properly it will have to be replaced, it's not possible to repair it.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Flywheel Key

If the lawn mower does not start the flywheel key might have sheared in half. The flywheel key is a small metal shim which fits into a slot in the crankshaft and engages with the flywheel. If the lawn mower blade hits a rock or other solid object the sudden stoppage of the blade can cause the flywheel key to shear. The only way to know for sure if this is the problem is to remove the flywheel and inspect the flywheel key.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Ignition Coil

If the lawn mower engine does not start the ignition coil might be defective. All small engines have an ignition coil. The coil is the device that provides spark for the spark plug(s). If the coil is bad, power won't get spark to the plug(s). The coil is essentially a small, induction generator. It is mounted next to the flywheel. The flywheel has one or more strong, embedded magnets. As the flywheel spins, the magnet(s) zip past the induction coil, this action of a magnet passing past a coil induces a voltage. Depending on the design of the coil and the strength of the magnets, a stronger or weaker spark can be created and delivered to the spark plug(s). Each time the flywheel spins around a spark is generated. The best way to test the ignition coil is to use a spark plug tester to see if the spark plug is getting a spark. If it is, the ignition coil is working properly.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Fuel Filter

If the lawn mower does not start the fuel filter might be clogged. The fuel filter is usually inline with the fuel line coming from the gas tank. Its purpose is to trap sediment and contaminants from the fuel. Over time it can become clogged and not let enough fuel through. It can't be cleaned but must be replaced if needed.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

On - Off Switch

If the lawn mower engine does not start the on/off switch might be turned off or defective. Test the switch with an Ohm meter or continuity checker.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Safety Switch

If the lawn mower does not start the safety switch might be defective or it might be sensing a problem with the lawn mower, preventing the engine from starting. Normally the safety switches can be checked for continuity with an Ohm meter or continuity checker. If it has continuity it's OK. If not, replace it.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

On-Off Switch

If the lawn mower engine does not start the on-off switch might be turned off or defective. Test the switch with an Ohm meter or continuity checker.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Rewind Spring

After pulling the starter rope and letting it go the rewind spring is supposed to recoil the rope onto a pulley. If the rewind spring is broken the rope can't be recoiled onto the pulley which will prevent it from turning over the engine, and then it does not start. Many rewind springs can be replaced but it's sometimes easier to replace the whole recoil starter assembly.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Rewind Pulley and Spring

When the starter rope is pulled and let go, the rewind pulley and spring is supposed to recoil the rope onto the pulley. If the recoil spring is broken the rope can't be recoiled onto the pulley which will prevent it from turning over the engine, and then it does not start. Many recoil springs can be replaced but it's sometimes easier to replace the whole rewind pulley and spring assembly.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Recoil Spring

When the starter rope is pulled and let go the recoil spring is supposed to recoil the rope onto a pulley. If the recoil spring is broken the rope can't be recoiled onto the pulley which will prevent it from turning over the engine, and then it does not start. Many recoil springs can be replaced but it's sometimes easier to replace the whole recoil starter assembly.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Recoil Starter

When the starter rope is pulled and let go the recoil starter assembly is supposed to recoil the rope onto a pulley. If the recoil starter assembly is broken the rope can't be recoiled onto the pulley which will prevent it from turning over the engine, and then it does not start. Many recoil starter assemblies can be repaired but it's sometimes easier to replace the whole recoil starter assembly.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

To see parts for your lawn mower, you need to enter your model number on the right. The system will then display parts that are associated with your lawn mower.

Recoil Starter Pulley

When the starter rope is pulled and let go the recoil spring is supposed to recoil the rope onto the recoil starter pulley. If the recoil spring is broken the rope can't be recoiled onto the pulley which will prevent it from turning over the engine, and then it does not start. Many recoil springs can be replaced but it's sometimes easier to replace the whole recoil starter assembly.

Enter your model number for the best repair help results:


What is a model number, and where do I find it?

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