A John Deere mower turns over but won’t start when it isn’t getting the air, fuel, and spark required for combustion.
A plugged air filter, stuck choke, clogged fuel line, plugged air filter, dirty carburetor, bad fuel pump, clogged fuel tank vent, or dirty spark plug may be the cause of a John Deere mower not starting after turning over.
Always follow the safety precautions outlined in the operator’s manual. This includes removing the spark plug wire prior to making repairs.
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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.
9 Reasons a John Deere Mower Turns Over But Won’t Start
Stuck Choke or Incorrect Choke Setting
The first thing to check is the choke setting. The choke is used to restrict airflow. This is needed to start a cold engine. If you are starting a warm engine, the choke is not used and is placed in the off position.
When the choke lever is in the wrong position, your mower will have a hard time starting and may not start at all.
SOLUTION: Ensure the choke is in the on/closed position to start a cold engine and in the off / open position for a warm engine.
After starting a cold engine with the choke on, the choke lever must be adjusted to the off position once the engine warms up. Failure to make this adjustment will cause the mower to shut down.
If the choke is set correctly and you are still having airflow issues, check to make sure the choke plate is not stuck and the choke cable is moving freely. Use carburetor cleaner to help free a stuck choke plate and linkages.
A stretched or worn cable must be replaced with a new choke cable.
Plugged Air Filter
Next, check the air filter. This is another item that can keep the mower from getting sufficient air.
The air filter is required to keep dirt and debris from passing through the air intake and causing engine wear and tear.
When the filter isn’t cleaned or changed regularly, it can become plugged with so much dirt that it’s keeping sufficient air from passing through the filter.
I recommend starting each mowing season out with a new air filter and then cleaning it several times throughout the season. You may have to replace it more often if you are using the mower in very dusty conditions.
SOLUTION: Follow the instructions below to clean a paper air filter and foam pre-cleaner if your engine uses a pre-cleaner.
If you are unsure what type of filter is installed on your mower and its cleaning instructions, check out the operator’s manual.
You can find more information on air filters in Guide to Lawn Mower Air Filters: Differences & How to Clean Them.
Clean a John Deere Mower Paper Air Filter
- Remove the filter for the air filter housing. Be careful not to allow dirt to fall into the air intake.
- Use a clean dry rag to wipe out any dirt or debris left in the air filter housing.
- Tap your paper air filter against a solid surface to knock as much dirt out of the air filter as you can remove.
- Hold your paper filter up to a light source and look to see if you can see light shine through the element.
- Reuse a filter when you can see light.
- Replace the filter with a new one when you can’t see any light, the filter is extremely dirty or is damaged.
- Install and reattach the air filter cover. (If your push mower uses a foam pre-filter, clean it using the instructions below and install it before attaching the filter cover).
Clean a John Deere Mower Foam Pre-Filter (If used on your mower. Some engines will use a different type of pre-filter).
Do not confuse this with a primary foam filter. A foam pre-filter is an extra filter used with a paper air filter to trap dirt. NEVER add oil to a pre-filter or you will damage the paper filter.
- Inspect the pre-filter. Replace it if you find any tears or if it has become brittle.
- Wash the foam filter with water and mild dish soap to remove dirt and oil.
- Rinse with water until the soap is removed and the water runs clear.
- Lay flat and allow to dry. Placing the filter outdoors in the sun will speed up the drying process.
- Once dry install the foam pre-filter with the paper primary filter and reattach the filter cover.
Dirty Spark Plug
If you are getting sufficient air, check for adequate spark. Remove the spark plug using a 3/4″ or 5/8″ socket wrench. The size you need will depend on your engine model.
A dirty or damaged spark plug can cause an intermittent spark that may prevent your mower from starting and continuing to run.
SOLUTION: Check the spark plug using a spark plug tester. If you find the spark plug is very dirty or damaged, you should just replace it with a new spark plug.
If the spark plug is in good condition and a little dirty, you can attempt to clean a spark plug that is in good condition and just a little dirty. Use a small wire brush to remove the carbon buildup.
Reinstall the spark plug after you ensure the electrode gap is correct. Then securely attach the spark plug wire.
Because a good spark plug is essential to a good performing lawn mower, I recommend starting each season with a new spark plug.
You don’t want to let fuel sit in your mower for long periods of time. Old gas leaves behind varnish and sticky deposits that cause fuel restrictions and component failures.
To ensure you are running the right gas through your John Deere mower, always purchase fresh gasoline and consume it within 30 days. Stay away from gas with high ethanol levels.
Use gasoline with a minimum 87-octane rating and a maximum 10% ethanol content in all mowers with a 4-cycle engine. Older push mowers may use a 2-cycle engine.
Read more about choosing the right type of gas for a 2-cycle or 4-cycle engine in This is the Gas to Use in a John Deere Lawn Mowers.
SOLUTION: If you find old gas in the fuel tank, drain the fuel tank using a fuel siphon pump.
Fill the tank with fresh fuel in addition to a fuel stabilizer like Sea Foam to help clean the fuel system and reduce moisture. Read more about the benefits of Sea Foam here.
If you are able to get the mower to start after refilling it with fresh fuel, allow it to run for 10-15 minutes to allow the treated fuel to work its way through the fuel system. If you are not able to start it yet, keep proceeding through the list to find the root cause.
Plugged Fuel Filter
The fuel filter strains fuel coming out of the fuel tank to keep dirt from flowing through the fuel system. This prevents wear on the fuel components and engine.
The filter can become plugged when it isn’t replaced regularly. This will prevent a good flow of fuel from passing through the filter. A lack of fuel can cause the mower to turn over and not start.
SOLUTION: Replace an old or dirty fuel filter with a new fuel filter.
Clogged Fuel Line
Inspect the fuel line to make sure there are no kinks that may restrict flow. Then check for a fuel restriction that may have developed in the line.
As I mentioned earlier, old gas can leave behind gummy deposits that can get stuck in the fuel line. This will narrow the passageway so a good flow of fuel isn’t able to get to the carburetor.
Check for a fuel restriction in the fuel line by stopping the fuel flow using the fuel shut-off valve or fuel pinch-off pliers. Remove the line from the inlet port on the fuel pump if your mower uses a fuel pump) or the carburetor if it does not.
Place the hose end in a container and turn back on the fuel flow. The container must be placed lower than the fuel tank because fuel can’t run uphill without the assistance of a pump. Watch the flow coming out of the line into the container.
SOLUTION: When you aren’t getting sufficient fuel flowing through a fuel line, shut off the fuel supply and remove the fuel line from the mower.
Spray carburetor cleaner into the line to loosen the clog. Then, blow compressed air through the line to dislodge and remove the clog. Repeat using the carburetor cleaner and compressed air until the clog is removed.
Reinstall the fuel line once the clog is removed. Replace it with a new fuel line if the restriction is not removed or you find the fuel line is aged and beginning to crack.
Bad Fuel Pump
A John Deere uses a fuel pump when the carburetor is positioned higher than the fuel tank. The pump is required to work against gravity to move fuel uphill to the carburetor.
Most mowers use a vacuum fuel pump. This style of pump uses the vacuum of the crankcase to get fuel to the carburetor.
When the fuel pump cracks or fails to work correctly you will have to replace it. If you don’t see physical cracks or fuel leaking, you can take some steps to check the condition of the fuel pump.
Before you test the pump, ensure you are getting fuel to the inlet port on the pump. (If you are not, check for a blockage in the fuel line or fuel filter)
SOLUTION: Once you have confirmed fuel flow to the pump, remove the fuel line from the carburetor and place it in a container. Check your pump is working correctly by starting your fuel flow and starting your mower.
You should have a steady or pulsating flow of fuel coming out of the fuel line. If you do not, you need to replace the fuel pump.
If your John Deere uses an electronic fuel injection pump, obtain a pressure reading using a fuel pressure gauge. Refer to your operator’s manual for fuel pressure specifications.
Replace the fuel pump if the pressures are lower than the specification required by the engine manufacturer.
The carburetor’s function is to mix gas with air to form combustion in the engine. When the carburetor fails to work, your John Deere will not start because it isn’t getting enough gas.
Too often, the main culprit of a carburetor not functioning properly is old gas. Old gas leaves behind a varnish that may plug the fuel jet or cause the internal components to stick.
SOLUTION: When you find the carburetor isn’t working, you’ll need to attempt to clean it, replace any faulty parts, or replace it with a new one.
Before you tear apart your carburetor, do this first:
- Confirm you are getting good fuel flow to the carburetor.
- Remove the air filter.
- Spray carburetor cleaner into the air intake and start the mower. If it turns over and starts using the carburetor cleaner, chances are your carburetor is dirty. *Don’t use starter fluid*
- Proceed with disassembling the carburetor and cleaning it or replace it with a new one. You can find more detailed information in How to Clean a John Deere Carburetor: Step-By-Step.
Plugged Fuel Vent
The fuel tank must vent to equalize the air pressure inside that tank to the atmospheric air pressure. On a John Deere lawn mower, the vent is located in the gas cap.
When the vent becomes plugged and no longer allows air to pass through the cap, the fuel tank forms a vacuum. This vacuum keeps gas from getting to the carburetor. The lawn mower will turn over, but not start because of the lack of gas.
To determine whether or not your gas cap is the problem, loosen the cap and attempt to start the mower. If it starts, the gas cap may be the cause.
To further confirm the cap as being the problem, continue to let the mower run while tightening the cap. If it begins to sputter, shuts down, and won’t start again until you loosen the cap.
SOLUTION: Replace a bad gas cap that is no longer allowing the fuel tank to vent.
Still Having Problems with Your John Deere Lawn Mower?
As a John Deere owner, you will encounter a variety of problems over the life of the equipment. These can include problems with starting, dying while mowing, vibrating, cutting unevenly, and not moving.
To help you identify the reasons your mower is having problems, I put together a handy guide to help you troubleshoot your mower. Check out Common John Deere Lawn Mower Problems and Solutions.