Troubleshooting a Riding Lawn Mower That Won't Start

June 5, 2017

If your riding mower will not start (most of these tips are applicable to push mowers also):

  1. Make sure you have fresh fuel; dirty or old fuel will not burn. Consider an octane boosting additive.
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  3. Make sure the oil level is correct; too much or too little oil will prevent the mower from starting.
  4. Most riding mowers start only when in neutral and when the blades are not engaged; make sure the trans is in neutral and the blades are not engaged. Engage the brake and/or clutch.
  5. Ensure it's getting fuel to the carburetor by pulling the line at the closest inlet near the carburetor, then cranking; it should spurt fuel. Make sure if you put new fuel in the tank, that you purge the old fuel from the lines by this method.
  6. If you are getting fuel, the carburetor may be dirty from fuel setting in the bowl for a long time; take the carburetor apart by removing the brass bolt from the bottom of the bowl, and cleaning the bottom parts with carburetor cleaner.
  7. Make sure the seat switch engages when you sit squarely in the seat.
  8. Wear safety glasses when you use pressurized air to clean dirt off of the entire engine; leaves, dirt, and other foreign particles may prevent the engine from breathing. Keep the top of the flywheel and the fins on the flywheel clean.
  9. If the magneto(s) or the flywheel are rusty, you won't get spark; use emery cloth to sand the rust off of the flywheel and the magneto(s). You have to remove the magneto to clean the rust off. Get all the rust off; the flywheel needs to shine where it makes contact with the magneto(s).
  10. Dead batteries are usually bad batteries. If the battery is dead, and does not charge, you probably have a bad alternator, or a bad battery.
  11. Make sure you 'choke' the carburetor the first time you crank it. After some cranking, you may need to adjust the choke. Make sure the throttle is adjusted to the 'Start' position.
  12. The air filter must be clean: If your carburetor is starving for air, the mower will not start. Clean the filter with soapy water and a soft brush. Hold the filter to a light, or the sun; you should be able to see light through the filter. Try starting without the filter, but do not operate the mower without the filter.
  13. Grass build-up in the mower deck may prevent the mower from starting. Make sure to pull the spark plug when you tip the mower to bust the clogged grass away from the deck. Be aware that tipping the mower can cause oil to leak from the engine block into the cylinder, which will result in smoke from the muffler due to oil burning; it should just last a minute or less.

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170 Questions

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February 23, 2014

My mower just clicks when you turn the switch on. It has a new battery and belts. It only stated for a few seconds and died. Now all it does is click when you try to crank it.

By Preston


February 27, 20141 found this helpful
Best Answer

The fact that it just "clicks" when you try to turn it over may mean that the engine has seized up. Lack of oil mixed in the gas could lead to this. Also, you may want to try to replace the carburetor.


Plenty of "How-to" sites on Utube and choose a reputable online business for mower parts and they should allow you to return carburetor if that is not the problem.

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October 5, 2020

My riding mower will not start unless I charge the battery. Parts store says battery is good.


Bronze Post Medal for All Time! 105 Posts
October 5, 20200 found this helpful
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If the battery needs charging to start the mower normally this means that one solenoid inside the battery is bad or is going bad. If this is the case when the store tests the battery it can test fine on the battery tester. Considering the solenoid is going out in the battery and it takes a full charge to start a mower it is better to get a new battery or just keep charging the battery each time you want to use the mower until the battery finally dies and buy a new one.

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October 6, 20200 found this helpful
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Most likely your battery is in the final stages and does need to be replaced.
I feel sure the parts store did a fast check on your battery and they needed to do a slow check (takes longer of course) to find your problem.


Be sure to buy your battery at a store that has a good warranty on their batteries. I have usually found that Walmart carries most size batteries and their stock seems to be fresher than many other stores - even the parts stores.
Most of their batteries have a 2 year replacement - not a partial payment like most others.

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May 22, 2020

My rider won't start. I replaced the filter, plugs, and fuel pump. It's not getting gas. Any ideas? If I put gas directly into the carb it starts for a few seconds. The gas lines are clear.


Bronze Post Medal for All Time! 105 Posts
May 22, 20200 found this helpful
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Have you tried to clean out the injectors yet? When you pump the gas is it going into the gas lines. What I mean by this if you try and pump the gas and remove the gas line from the carburetor do you see gas coming out of the lines?


If not then there is an issue with the lines being plugged or you are having an issue with the new fuel pump not pumping the files through the lines. Have you tried to prime the fuel pump to get it pumping the fuel?

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Gold Feedback Medal for All Time! 949 Feedbacks
May 23, 20200 found this helpful
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That's a bummer!
Why did you decide to replace all those 'parts'?
Your mower would not start or would not run?
Have you been able to use it this season or had trouble from the beginning?
Did you put mower to bed last year with gas in the tank? If so, did you add any kind of gas storing additive?

If old gas you need to remove gas and use only new gas. You will need a Siphon Kit for removing gas. These are sold at Walmart or any auto parts store.


If you go to an auto parts store then you may need to also purchase a can of starting fluid. This is to spray into your carburetor to get it started and maybe clean out the fuel jets.
Also - if you did not replace the air filter (you just said 'filters' so gas? or?) this would be a good move.

You can discuss your problem with someone at the auto parts store and they may have some additional solutions to try.

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May 9, 2018

The ignition switch won't start the engine for my 12 hp Ranch King riding mower.


Bronze Post Medal for All Time! 107 Posts
May 10, 20180 found this helpful
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I was going to say, cleaning battery terminals and even making sure that the batteries are regularly maintained - some need water levels checked and added - can cure most of these sorts of problems

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June 3, 2021

Hi, I had checked the fluids before starting and I did a couple rounds. I had pause for a moment and had foot on the clutch and was idling on rabbit, I slow it down to middle and then let go of the clutch and then it stalled and it won't start again.

Just "rearing" but won't catch. What can I do about this simple problem?


Silver Answer Medal for All Time! 425 Answers
June 3, 20210 found this helpful
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Did you hold in the clutch AND also set the engine speed back to start position? It probably won't start with the speed set on rabbit. If you need to, read through your owner's manual for a little refresher on your mower operations.


Also, did your fluid check include the fuel? I know it seems like a no-brainer, but we all forget the simple things sometimes. Good luck.

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June 14, 2021

When I turn the key the B+G 12.5hp engine (lawn tractor) turns and then sticks. The starter is new. Is the next potential suspect battery or solenoid?


Silver Answer Medal for All Time! 440 Answers
July 1, 20210 found this helpful
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If your lawn mower starts, runs briefly, then dies these are the four most common reasons that's happening:

1. Loose carburetor
A loose carburetor will not let your engine function well because there will be an insufficient flow and atomization of gas due to unstable attachment of the carburetor. Check the carburetor first if it is fixed firmly before determining other problems.

2. Dirty carburetor or clogged carburetor bowl
Your engine needs a steady flow of gasoline to run correctly. The carburetor is responsible for mixing gas with just the right amount of oxygen to create combustion. This combustion supplies a continuous rotation of the crankshaft that is necessary to run the mower's engine. If your carburetor is dirty or the carburetor bowl is clogged, the process above is compromised, and your engine may start up, but it will not run properly - turns and then sticks.
Unscrew the carburetor bowl and give it a once over with the cleaner - blowout your dirty carburetor with an aerosol of carburetor cleaner. Be sure to clean the screw and hole with the carburetor cleaner as well. When reattaching the bowl, don't over-tighten the screw. This could strip the threads enough to distort the seal.

3. Old gasoline in your mower
If the gas in your mower has been sitting inactive for a while, evaporation has most likely created a damaging residue. This residue leaves particles that clog your mower's internal parts and the end result is restricted gas flow - your mower can start and die shortly thereafter. Sometimes, your mower won't start at all.
If your mower tank is less than half full of old gas, you might try adding new gas to dilute the impurities. If the old gas is more than half of a tank, it would be best to siphon it out and fill the tank with fresh gasoline.
Adding a stabilizer prevent the clogging residue for up to two years. Always read the directions to know the proper fuel to stabilizer ratio for your mower.

4. Dirty or defective spark plugs
Spark plugs supply the "spark" that ignites the air / fuel mixture in your engine. If they are dirty or faulty, they will not spark, and your mower will not start, or may start and then quickly die.
If your spark plugs are not too heavily coated with build-up, you can try cleaning them. You should never clean a spark plug with a shot-blasting cleaner. A wire brush and appropriate cleaner will do the trick if the plug is just dirty. However, if your mower's spark plug looks filthy or appears to have a dark carbon residue, you might be better off replacing.
Spark plugs should be replaced every year or two.
Replacing a spark plug can be a bit more challenging for a first-timer, but it is an easy job. If you have never done this before, there are several videos online that can be of great assistance

5. Blocked gasoline cap
If this hole gets blocked, this can create a vacuum inside the tank and there will be a disruption of the gas moving downward into the carburetor.
Clean the hole in the cap with a thin wire or if the cap is already beaten up, replace it with a new one.

6. Too much oil in your resevoir
If your carburetor is clean and the spark plugs are firing, the problem might be too much oil. If a lot of smoke is coming out, your mower might be running, but not for long. In this case, the excess oil will eventually drown out the engine and cause it to die.
You just need to drain some. Use a dipstick to measure the amount of oil in the reservoir before removing it, and then again after to make sure you get the right level. Not enough oil is another (and more serious) problem.

7. Worn-out carburetor
If your lawnmower has served you for years and undergone many repairs, the carburetor will be the first one that must be replaced followed by other replaceable parts.

8. Clogged air filter.
Replace the filter.

If your problem still is not fixed, then call a professional.

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April 30, 2017

My brother has an old riding mower (90s I think) that won't start. He put in fresh gas, a new battery, and fresh oil, but the engine won't start. He says it's just making a click, the motor shakes, but nothing happens.

He is tight on money and can't afford major repairs or parts. Any suggestions on what's wrong with it and how to fix it?


Gold Post Medal for All Time! 677 Posts
April 30, 20171 found this helpful

The switch is under the seat. Disconnect it and reconnect it.

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April 30, 20170 found this helpful

new spark plugs? Does the carb have old fuel in it?

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Diamond Post Medal for All Time! 1,246 Posts
April 30, 20170 found this helpful

Clean out the carburetor and it should do the trick

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Bronze Feedback Medal for All Time! 141 Feedbacks
May 5, 20170 found this helpful

I have had pretty good luck cleaning the carburetor. Then if it still doesn't start up, add some fuel cleaner to the tank. Follow the directions for the amount. Even with new gas, there still can be some bad gas or moisture in the system.

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July 18, 2021

Scot S16/42 Riding Mower (Kohler engine) won't turn over. I have a good battery, new starter motor, new ignition switch, new starter solenoid, good gas, good spark plug, clean air filter, all safety switches work properly - all the normal stuff that prevents a riding mower gas engine from starting checked.

When I turn the key, (yes gas valve is turned on: throttle lever in start/chock position), nothing happens, no click...nothing.

If I use a jumper cable from the positive battery post and touch it to the positive electric starter motor (key in run position), the starter motor will turn over and start the engine.

Sometimes, when turning the key normally to start the engine, nothing happens until I start moving the throttle lever back and forth from the start/fast to normal run rpm's position simultaneously whilst holding the key in the start position - then starter motor turns over, and starts the engine. This is weird!

I have a walk behind mower that wouldn't start and I finally figured out that the safety kill lever cable was stretched and kept the engine grounded. Once I changed out the stretched cable with a new one, the mower started on the first pull every time.

So my question is - does this throttle cable on my SCOT's riding mower also work as a cut-off the electricity ground like the walk behind mower has? if so, the problem might be the same - stretched cable? Or something else going on?

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July 15, 2019

I have a Yard Machine riding lawnmower that won't start. It has good gas and the oil is good. So id the battery. It turns over strong. The only way to get it to fire off is to either pour gas in the intake or cover the intake to restrict the air from intake, but it will die as soon it it fires off.

Fuel is in carb bowl and it's been cleaned.

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May 21, 2017

I was cutting the grass. I got off my Snapper rider to pick up trash. The mower died and won't start back up. It is like a dead battery, but the battery is good. Could it be the solenoid?

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May 10, 2017

I have a Scott's riding mower with a 17Hp Briggs and Stratton motor. It won't turn over after mowing the grass last week. It needed a new battery and air filter.

There is gas or oil in the air filter and it back fires out of the air filter, with fames an all. Any help? I changed the plugs and oil before storing it this winter.

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