Going out to your storage shed to find the lawn tractor will not start can be frustrating. Getting your tractor started to get your mowing completed is a top priority.
A lawn tractor will not start when it can’t get sufficient air, fuel, or spark for combustion in the cylinder.
This is due to a clogged air filter, old fuel, bad fuel cap, bad fuel pump, clogged fuel lines, dirty carburetor, bad spark plugs, faulty ignition coil, bad battery, or a blown fuse.
I will address these issues along with a few other items that can cause your lawn tractor to not start. Take all safety precautions as outlined in your owner’s manual before working on your equipment.
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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.
15 Reasons Your Lawn Tractor Won’t Start
Fuel Tank is Empty
You know your lawn tractor requires fuel to run, but you may have overlooked the simple steps when frustrated. Check your fuel supply. If you believe you are going through fuel more quickly than normal, look for a fuel leak on your tractor.
FIX: Add fresh fuel to an empty fuel tank
Bad or Old Fuel
Right type of Fuel for your lawn tractor
There are both gas-powered and diesel-powered lawn tractors. If you have a gas-powered lawn tractor, make sure you are using the right type of gasoline. With so many different gasoline mixes offered at the fuel station today, it can be easy to purchase the wrong fuel.
A gas-powered lawn tractor uses unleaded gasoline with a minimum 87-octane rating and a maximum ethanol content of 10%. Do not use gasoline with a higher ethanol content like E15 or E85 (15% ethanol and 85% ethanol respectively).
Ethanol is being added to gasoline to make fuels a little more environmentally friendly. While ethanol is okay to be used in most vehicles, it is not good for the engine in a lawn tractor.
Read more about the right unleaded gasoline to use along with the effects of ethanol in this article.
Fresh fuel for your lawn tractor
Fresh fuel is required for your lawn tractor whether your tractor is diesel or gas-powered. Fuel can begin to break down as quickly as 30 days after purchase.
Not only is it important to purchase and use the fuel timely, but it is also important to purchase gasoline from busy gas stations where fuel isn’t sitting in storage tanks for long periods of time.
Sediment and a gummy solution can form in diesel fuel from oxidation and microbial growth over time. Moisture can cause gummy solutions to form in gasoline as well.
Because fuel can degrade and become damaging to the fuel system, you must not let fuel sit around for a long time.
If you are unable to use it within a month, stabilize your fuel with a fuel additive like Sea Foam motor treatment. Read more about the advantages of Sea Foam here.
FIX: Drain the fuel tank using a siphon to remove old fuel. Add fresh fuel that includes a fuel additive to stabilize and clean your fuel system.
Bad Fuel Cap
Your lawn tractor fuel cap is designed to vent and allow air to pass through the cap. Without a vent, the fuel tank will act like a vacuum preventing fuel from leaving the fuel tank. Without fuel, your lawn tractor will not start.
To troubleshoot this problem, remove your gas cap, start your tractor, and let it run. Be careful and don’t let any contaminants enter the fuel system with the cap off. If it starts and runs fine without the cap, replace the cap and continue to allow your lawn tractor to run.
If your tractor dies after running for a while, it is likely your fuel cap vent is plugged.
FIX: You can try to clean your cap and remove the clog in your fuel cap. You must replace the cap if you are unable to unclog the cap so it sufficiently vents.
Bad Spark Plug
Gas Engine: Bad or dirty spark plugs can prevent your lawn tractor from starting. Inspect the spark plugs for cracked porcelain, burnt electrode, or excessive dirt caused by carbon and oil buildup.
You can try to clean dirty spark plugs. If the plugs are very dark in color or damaged, they must be replaced.
Make sure your spark plugs are gapped according to the engine manufacturer’s specifications. Also, check that the wires are securely attached.
FIX: Replace any damaged or faulty spark plugs on your lawn tractor with new plugs. Secure all leads.
Plugged Air Filter
Your lawn tractor’s engine requires clean air to run. When using your tractor, debris, and dirt will collect around the air filter. If you don’t regularly check and clean your filter, it can become so plugged, your tractor isn’t able to get air and won’t start.
Something as simple as a plugged filter can create many problems in your lawn tractor. It isn’t something that should be overlooked. A plugged air filter can cause the engine to overheat resulting in a significant repair bill.
FIX: Take time to clean your air filter by following these steps:
Clean a paper air filter element in a lawn tractor
- Remove your filter from the air filter housing
- Wipe out any dirt remaining in the filter housing. Use a dry clean cloth. Don’t allow any dirt or debris to fall into the air intake.
- Tap your filter against a solid surface to loosen and remove as much dirt as you can get out of the filter.
- Hold the filter up to a light source to check to see if it can be reused or needs to be replaced. If you can see light shine through the paper element, go ahead and reuse it otherwise install a new one.
- Reinstall the air filter housing cover.
Bad Fuel Pump
Most lawn tractors use a vacuum fuel pump. This pump can go bad over time and will not be able to draw fuel out of the fuel tank using the vacuum off the engine to move fuel to your carburetor. Fuel running through your fuel pump can degrade the plastic and internal components.
Check for signs of fuel leakage on your pump. You will need to replace the pump if you find leaking as this is a sign your pump is no longer sealed and able to work correctly.
If you don’t see signs of leaking, you’ll have to test fuel flow to check for a pump failure that caused your lawn tractor not to start.
Using your fuel shut-off valve or clamps on your fuel lines to stop and start fuel flow, you need to check for fuel flow to the pump.
Once you verified you are getting fuel to the pump, check your pump to make sure a steady or pulsating flow of fuel is coming out of the outlet port on your pump.
FIX: Replace your lawn tractor’s fuel pump if you are not receiving a constant or pulsating flow out of the pump.
Plugged Fuel Filter
A lawn tractor’s fuel filter screens the fuel to prevent dirt and other contaminants from entering the fuel system and engine. Gummy deposits and dirt can clog the fuel filter keeping fuel from flowing through the filter.
It is good practice to replace the fuel filter annually to minimize the likelihood of your fuel filter becoming plugged during the mowing season.
FIX: A clogged fuel filter must be replaced with a new one. A fuel filter has an arrow on the side of the plastic inline filter. This arrow indicates which direction to install your filter.
A fuel filter must be installed with the arrow pointing in the direction of your fuel flow. The arrow should be pointing toward the carburetor and away from the fuel tank.
Clogged Fuel Line
Gummy deposits created by running old fuel can clog the fuel lines. Because you can’t see through your fuel lines, you will have to start and stop the fuel flow while removing an end of a section of the fuel hose to check the fuel flow.
Use the fuel shut-off valve located at the bottom of your fuel tank to start and stop the flow. You can also use fuel hose crimp pliers to crimp the line and stop the flow.
With your fuel flow stopped, remove one end from a section of the fuel line (the end furthest from the fuel tank) and place it in a container.
The container must be placed lower than the fuel tank. Fuel can’t run uphill without the assistance of a fuel pump. Turn on your fuel flow and check for sufficient fuel flow into the container.
FIX: Once you find a clogged line, try to remove the blockage by spraying carburetor cleaner into the line to help loosen the blockage. Follow this by blowing compressed air through the line until the fuel line is no longer clogged.
If you notice the fuel line is dry and brittle or you are unable to remove the clog, you must replace your fuel line with new fuel line.
Clogged & Dirty Carburetor
Old fuel can also clog your carburetor on a gas-powered lawn tractor so it no longer regulates the amount of fuel mixed with air to form a combustion in the cylinder.
When fuel can no longer be regulated because the carburetor components have become plugged or stuck from running old fuel, your lawn tractor will run rough and possibly not start.
FIX: If you are a little mechanical and comfortable with working with small parts, you should be able to handle cleaning your carburetor. You can also have your local small engine mechanic clean your carburetor if you choose not to tackle the project.
You can find steps to clean your carburetor on your lawn tractor here. If your carburetor is too dirty to clean adequately or internal components have failed, you have the option to rebuild the carburetor or replace it.
Bad Battery, Loose Cables, or Corroded Terminals
Your lawn tractor will not start with a bad battery, loose cables, or corroded terminals. Confirm your battery terminals are not corroded and are attached securely to the battery.
FIX: Clean corroded terminals in a baking soda solution containing 2 cups of water and 3 rounded tablespoons of baking soda. Use a wire brush to scrub the terminals clean.
Test your battery with a multimeter. You need a reading of about 12.7 volts. Place on a charger to charge your battery if your reading is less than this.
Read more about the steps and items needed to charge your battery here. If your riding lawn tractor battery does not hold a charge, you will need to replace it with a new battery.
Bad Safety Switch
Your lawn tractor uses safety switches to assist with its safe operation. You will have a safety switch that disengages the deck when it does not sense the operator is in the seat.
It also has a safety switch that will prevent your lawn tractor from starting when you don’t have the parking brake engaged. Your tractor may have additional safety switches. When a switch fails, your tractor may no longer start.
FIX: Test the switch using a multimeter or you can temporarily bypass the safety switch to identify a bad switch. Never operate a lawn tractor without a working safety switch.
Never run a lawn tractor when a safety switch is bypassed. You never know when you will encounter a situation where the safety switch can save you from serious injury.
Bad Ignition Switch or Ignition Coil
When you insert your key into the ignition switch and nothing happens or it just doesn’t feel the same when you turn your key, you have a bad ignition switch preventing your lawn tractor from starting. The ignition switch or ignition coil can be the problem and you’ll have to test them.
FIX: You can use a multimeter to test the ignition switch. Replace the switch if bad. After you have checked your spark plug is working, check the continuity of your ignition coil using a multimeter. Replace the ignition coil if you find a break in the continuity.
Blown Fuse
A fuse is installed to protect your lawn tractor’s electrical system. Check your tractor to make sure you don’t have a blown fuse.
The location of the fuse block can vary depending on the manufacturer of your lawn tractor. A good place to start is looking around your battery. It may be placed under or next to this area. You may also find the fuse behind your dash.
FIX: Replace your blown fuse. Use a fuse with the same amperage as the fuse you are replacing. If you continue to blow fuses, you should bring your lawn tractor to your local repair shop or your local lawn tractor dealership to troubleshoot the root cause of the electrical failure.
Faulty Charging System
While the charging system isn’t the main reason your lawn tractor won’t start, it can contribute to a weak battery 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.
FIX: Have your local repair shop check your charging system to isolate the problem. If you don’t have experience with charging systems, you will most likely just be replacing electrical items until you find one that works.
This can get very expensive because most parts stores won’t let you return electrical parts if you find a part you purchased doesn’t resolve your starting problem.
Incorrect Starting & Operating Procedure
There are special operating procedures that must be followed to start and operate your lawn tractor. Some of these are safety procedures while others are controlling the throttle and choke to start the tractor.
FIX: Refer to your operator’s manual to ensure you are operating your lawn tractor correctly, so you don’t set off the safety features that prevent your tractor from starting.
Still Having Problems with Your Lawn Tractor?
You can encounter many different types of problems with your tractor as it ages. I have put together a guide to help you quickly identify the causes and solutions for the type of problem you are encountering.
I cover common problems like a lawn tractor not starting, smoking, cutting unevenly, vibrating, dying after running, and more.
Check out my guide: Common Lawn Tractor Problems & Solutions.
If you encounter a problem you don’t feel comfortable troubleshooting or repairing, contact your local lawn tractor dealership or repair shop for assistance.