You’re mowing the lawn as usual, but this time the engine doesn’t seem to give the power it once did. You know your mower best. When you notice this loss of power, it’s important to find the cause.
It could be something as simple as a maintenance problem or operator error. It could also be a more significant problem that can cause engine damage if it is not addressed.
A zero-turn lawn mower may experience a loss of power when an increased load is placed on the engine due to operating at a fast ground speed; cutting wet or tall grass, or having a plugged mower deck. An air or fuel restriction; low engine oil level; or poor air circulation can also cause a loss of power in your zero-turn.
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.
Reasons Your Zero Turn Mower Has No Power
Zero Turn Has Too Much Load Placed on the Engine
When too much load is put on your engine, you can lose power. This extra load requires the engine to work harder. These are items that can put your zero-turn under load:
Ground Speed is Too Fast for Mowing Conditions
Mowing your lawn at too fast a speed can put extra load on your zero-turn. Slow down the speed to match your mowing conditions. For example, your engine works harder to mow thick lawns over thinly covered lawns.
You need to operate your zero-turn at a slower speed when mowing thick lawns. Operate your mower slower when on inclines. Mowing inclines makes your engine work harder.
Mowing Wet or Tall Grass
When mowing wet or tall grass, you are making your engine work so much harder than mowing dry grass with a manageable length. Mow your grass when it is dry.
This puts less load on your engine and reduces the number of grass clippings clumping and collecting under your mower deck.
It is best to mow regularly to prevent your grass from getting excessively tall. When mowing tall grass, adjust your mower deck to its highest setting for the first cutting and then lower the deck for the next cutting.
Avoid mowing in these conditions if possible. If you do need to mow this type of grass, slow down your zero-turn speed to not overwork it.
Grass Buildup Under Your Zero Turn Mower Deck
Keep your mower deck clean so the blades can spin freely. When dirt and grass clippings plug the mower deck, the engine is required to work hard to turn the blades through the buildup with each revolution.
Regularly scrape your deck to remove debris. Avoid mowing in wet conditions as the grass is more likely to build up under your deck. Not only does this extra debris under the deck cause your engine to work hard and lose power, but it also causes your zero-turn to give you a bad cut.
Running Dull Zero Turn Mower Blades
What further magnifies the lack of power received when mowing with a clogged mower deck, is mowing with dull mower blades and a clogged mower deck.
Check your blades and sharpen or replace them if needed. You can find more information on inspecting your blades and the sharpening process here.
Plugged Zero Turn Air Filter
When you feel you are losing power when running your zero-turn, check your air filter. A plugged air filter can cause a power loss.
Your engine requires air to run. When it no longer gets the air it needs, the engine may run sluggish and possibly quit. Regularly check your air filter condition. Clean and replace as needed.
How to Clean Your Zero Turn Paper Air Filter Element
- Remove the air filter from the air filter housing.
- Wipe out any remaining dirt in the housing with a dry cloth. Be careful not to allow dirt to fall into the air intake.
- Tap your air filter against a solid surface to knock as much dirt loose as possible.
- Hold your filter up to a light source.
- Reuse your filter if you can see light through the paper element.
- Replace with a new filter if you can’t see light through the paper element.
Old Fuel in Your Zero Turn Mower
Fuel that has been sitting around for long periods can break down and become less effective. It can develop gummy substances and deposits that can cause blockages in your fuel system which can result in a power loss.
Most people don’t realize fuel can begin to become less effective and unstable as quickly as 30 days after purchase. It’s important to use the fuel in your zero-turn quickly. If you are unable to use your fuel timely, use a fuel additive to stabilize your fuel.
Drain your bad fuel into a container for recycling. Refill with fresh fuel. Most gasoline-powered zero-turn mowers use unleaded gasoline that has a minimum octane rating of 87 and a maximum ethanol content of 10%.
Do not use a fuel with a higher ethanol content because ethanol is not good for small engines. Learn more about the right fuel to use in your zero-turn and stabilizing your fuel with an additive in my other articles.
Clogged Fuel Filter or Fuel Lines on Your Zero Turn
Dirt and the substances left behind by running old fuel can cause your fuel filter to become plugged and your fuel lines to become clogged. This fuel restriction can cause your zero-turn to feel a loss of power and run sluggishly.
It is good practice to replace your fuel filter annually when performing your routine zero-turn maintenance. This filter is a rather inexpensive part that can prevent fuel supply issues and significant engine damage if it fails to strain dirt efficiently.
Check for clogs in the fuel lines by starting and stopping fuel flow using the fuel shut-off valve located on the bottom of your fuel tank or by crimping the fuel line. Stop your fuel flow.
Remove the end furthest from the fuel tank of one section of the fuel line and place it in a container. Start flow to check for blockages. Continue checking other sections of the fuel line.
When you find a clogged fuel line, remove the section of the line and spray carburetor cleaner into the line. This should help loosen up the clogs.
Follow this by blowing compressed air through the line to free the obstruction. If you cannot remove the blockage or you notice your line is dry and cracked, replace it with a new fuel line.
Dirty Carburetor on Your Zero Turn Mower
Your carburetor is an important component of your mower. It regulates the correct amount of fuel and air allowed in the cylinder for combustion.
The substances left behind by running old fuel can collect in your carburetor preventing it from providing the fuel needed to run. It may even keep your zero turn from starting.
When this happens, the dirty carburetor can cause your mower to experience a loss of power. Clean a carburetor that isn’t allowing fuel to get to the cylinder. Before you tear your carburetor apart, remove the air filter and spray carburetor cleaner into the air intake.
Start your engine to see if it will run. If it runs, but it won’t stay running, you need to clean your carburetor. Refer to the article to find step-by-step instructions to clean your zero-turn carburetor.
Bad Spark Plug Causes a Zero Turn Mower to Lose Power
A fouled spark plug in your zero-turn can cause an intermittent spark that can cause a loss of power. Inspect your spark plug for signs of carbon, dirt, and oil buildup on the tip.
If you find a dirty or damaged spark plug, I recommend replacing it with a new one to ensure you’re running a good plug in the mower.
If you choose to, you can attempt to clean it with a wire brush and reuse it if the spark plug is in good condition and not very dark in color.
Low Engine Oil Level on Your Zero Turn Lawn Mower
When your zero turn doesn’t have enough engine oil in the crankcase, the engine will experience a loss of power. The lack of lubrication from not having enough oil causes increased friction.
This friction builds heat and causes the engine to get extremely hot and suffer from power loss.
If a low engine level isn’t caught quickly, the increased heat will cause internal engine parts to melt. This can result in a significant engine repair bill or possibly an engine replacement.
Routinely check your engine oil level before each mowing. This doesn’t take too much time and can help you catch oil leaks or engine problems early. Always run the correct amount of oil in your engine. Not doing so can cause running and overheating problems.
When you find your engine doesn’t have enough oil, add oil to bring the level to the manufacturer’s recommended level.
If you continue to have engine problems, running your zero-turn mower with low engine oil could have caused internal damage that needs to be diagnosed by an experienced small engine mechanic.
Too Much Engine Oil Causes a Zero Turn Mower to Lose Power
Overfilling the crankcase with engine oil will cause your engine to smoke. Increased pressure builds as a result of too much engine oil and oil can be pushed into the cylinder through the valve train. When this happens, a bluish-white smoke is emitted when the oil burns in the cylinder.
This thick cloud of smoke can plug your air filter causing running issues because your engine isn’t able to get the clean air it needs. Check your air filter and your spark plug, and clean or replace them if needed.
Continuing to run your zero-turn with too much oil can cause seal damage, the engine to hydro lock, and a bent piston rod. Correct an engine with too much oil by removing a little oil. You can do this by using an oil evacuator, a drain plug, or even a turkey baster.
Zero Turn Engine Air Circulation is Blocked
Your engine needs to be kept cool to prevent it from overheating and losing power. Make sure your engine has good air circulation by removing any grass clippings, dirt, and debris that may be collecting around your engine.
Remove all the debris that has been collected under your engine shroud.
Engine Cooling Fins are Dirty on Your Zero Turn
The cooling fins are essential to circulating air around the engine to keep it cool. Just like you need to remove debris from collecting around your engine so your engine doesn’t overheat and experience a loss of power, the same is true of your cooling fins.
The fins can become plugged with mud and grass clippings inhibiting the amount of air is it able to push to the engine. Clean out debris around your cooling fins and replace any broken fins to make sure it is functioning properly.
Still Experiencing Loss of Power in Your Zero Turn?
While most reasons your zero turn has no power are due to a lack of air or fuel, there are a few other electrical and internal engine issues that can result in a loss of power.
If you are still experiencing problems after you have checked the items listed above, it’s time to take your mower to a knowledgeable lawn mower mechanic for further diagnosis.
Still Experience Problems with Your Zero Turn Mower?
Many different types of problems can develop in a mower. It doesn’t matter what brand you own.
While some mowers are built with stronger materials, bigger filters, better engines, and tougher spindle housings, they are all going to break down and cause issues at some time. Some may just not develop problems as quickly as others.
I put together a guide with common things that go wrong on zero-turns. In this guide, you will find a list of causes and solutions for a mower dying, smoking, vibrating, not starting, having cutting issues, and more.
Check out my guide at Common Zero Turn Mower Problems: How to Fix Them
If you still can’t find the solution to your problem or you don’t feel comfortable troubleshooting or repairing your mower, it is best to have an experienced mechanic check out your mower.
You can visit your local dealership that provides repair support for your brand mower. You may also find a lawn mower repair shop with experienced small engine mechanics.