Why a Cub Cadet String Trimmer Won’t Start (SOLVED)

You should make an effort to fix your string trimmer following the advice that is provided below before you conclude that it has reached the end of its useful life.

When the engine of a Cub Cadet string trimmer is deprived of the appropriate amounts of air, gasoline, and spark, the machine will not start.

It’s possible that this is the result of a clogged air filter, a broken spark plug, a blocked fuel filter, a clogged fuel line, a filthy carburetor, a malfunctioning recoil starter, a clogged spark arrestor, a clogged fuel tank vent, or old gasoline.

It’s possible that the inability to start your Cub Cadet is due to nothing more than a flooded engine.

Remove the spark plug wire from your string trimmer and wait for all of the moving components to become still before attempting any repairs. In the operator’s handbook that came with your Cub Cadet product, you’ll find instructions on how to properly use safety measures for your string trimmer.

outdoorstip Cub Cadet String Trimmer

Causes of the Beginning Issues You’ve Been Experiencing with Your Cub Cadet String Trimmer

If it has been some time since you last serviced the vehicle and it has been a while since you did so, you should think about changing the fuel filter, the air filter, and the spark plug. Doing so would allow you to rule out the possibility that these preventative maintenance items are the cause of the difficulty you are having starting the vehicle.

It is highly suggested that you replace these components as part of the routine maintenance that you do on your Cub Cadet. You can find more information about this recommendation here.

1. I attached an Air Filter to a Cub Cadet String Trimmer and Wired It In

The engine receives protection from the air filter, which prevents foreign particles such as dirt and trash from entering the air intake. It is essential to ensure that your Cub Cadet string trimmer has a functioning air filter at all times.

In spite of the fact that it serves to protect the engine, the air filter should be cleaned regularly to avoid any potential complications. When the air filter accumulates so much dirt that it gets clogged, it may prevent an adequate amount of air from flowing through it.

The lack of oxygen in the cylinders prevents the engine from starting. If you discover that this is the cause of your issue, you should make it a habit to always use your string trimmer in conjunction with an air filter.

This might turn out to be a very expensive error. It is possible for dirt to get into the air intake and cause damage and wear to the engine. It is possible that the string trimmer may get so damaged that it will need to be replaced.

SOLUTION: Take off the air filter and clean the housing of the air filter, being sure to remove any leftover dirt. If the air filter is unclean, you should replace it with a new one.

2. A String Trimmer from Cub Cadet with a Defective Spark Plug

Due to the accumulation of carbon over time, the spark plug will eventually get tarnished. It’s possible that this may cause the plug to misfire, leading to starting issues that come and go.

Additional things to watch out for include broken porcelain or a scorched electrode, a spark plug wire that is too slack, and an improper spark plug gap. Your Cub Cadet can also have trouble starting if any of these things are present.


A wire brush may be used to make an effort at cleaning a filthy spark plug so that it can be reused. It is better for me to replace it. It is a relatively affordable component, and it is one of the major components that ensures the smooth operation of your string trimmer.

You need to check that the gap on your spark plug is set according to the manufacturer’s specifications and that the spark plug wire’s boot is fastened firmly.

3. Plugged Fuel Filter in a Cub Cadet String Trimmer

The gasoline tank houses a relatively modest component known as the fuel filter. It is hooked to the gasoline line and may be found there. It is responsible for preventing debris and other potentially harmful substances from entering the fuel system.

If the filter is not replaced on a regular basis, it will eventually get clogged. This will restrict the quantity of gasoline that is delivered to the carburetor, which may result in starting problems.

SOLUTION: Within the gasoline tank, you will find the fuel filter that has to be replaced.

  • Clean the area surrounding the fuel cap by wiping it down to remove any loose debris and ensure that it does not enter the fuel tank.
  • Take off the cap of the gasoline tank.
  • Get permission to use the filter. Hooking the gasoline line with a clean wire that has been bent works nicely in order to remove the filter from the tank.
  • It is necessary to remove the old filter from the fuel line.
  • Replace the fuel filter with the new one and make sure the gasoline line is attached to the filter securely.
  • After that, replace the gasoline tank cap and make sure the filter is properly positioned within the tank.

4. An improper mixture of fuel in a Cub Cadet string trimmer (2-Cycle Engine)

String trimmers manufactured by Cub Cadet and powered by two-cycle engines need a fuel combination consisting of oil and gas. If you put undiluted gasoline through your trimmer, you will cause the engine to seize. Your string trimmer will be severely damaged if you use it in this manner.

There is an incredibly low level of gas. Without the additional oil, the engine will not get the lubrication that is necessary for the moving components on the inside to be able to do their jobs.

The fuel combination for a two-cycle Cub Cadet string trimmer is 40 parts gas to one part oil. A 40:1 ratio equals 40 parts gasoline to 1 component oil.

Use unleaded gasoline with a minimum 89 octane rating (mid-grade) and a maximum 10% ethanol content when you are making the oil and gas combination for your Cub Cadet string trimmer. This will ensure that the engine runs smoothly.

Add a 2-cycle premium oil that is approved to operate with air-cooled engines by both ISO-L-EGD and JASO M345 FD. This oil should be intended to function with air-cooled engines. Avoid using ordinary motor oil as well as 2-cycle oil for outboard motors.

Before adding it to your string trimmer, you should first mix it in a gas can that has been certified.


First, the fuel tank should be drained, and then it should be refilled with the appropriate ratio of gas to oil. If the issue persists, have a technician that specializes in repairs for small engines analyze the problem and decide whether or not it can be fixed in a way that is economical.

Here you will be able to discover further information on the correct kind of gas to use in your Cub Cadet string trimmer.

2-Cycle Premixed Fuel

Using a gasoline blend that does not include ethanol is a fantastic choice that may cut down on fuel-related issues and increase the life of an engine. This oil and gasoline mixture does not include any ethanol and is already prepared to be poured into the fuel tank of your string trimmer.

You won’t have to worry about the negative consequences of ethanol, which were addressed in the section about gasoline earlier. When you need it, having gasoline already on hand on your shelf is not only helpful but also handy.

TruFuel also offers a decent 40:1 premixed fuel.

Gas and oil mixture for the Cub Cadet 2-Cycle Engine

Mixture1 Gallon Gas2 Gallon Gas2.5 Gallon Gas
40:13.2 oz Oil6.4 oz Oil8.0 oz Oil
Cub Cadet 2-Cycle String Trimmer Gas to Oil Mix

5. Using the Incorrect Fuel Type in a Cub Cadet String Trimmer (4-Cycle Engine)

Straight gas is required for use with Cub Cadet string trimmers that have a 4-cycle engine. Choose a kind of unleaded gas that has an octane value of at least 89 and contains no more than 10% ethanol.

Steer clear of fuels that contain a high percentage of ethanol, such as E15 and E85 fuels. It is preferable to use a gasoline that does not include ethanol.

SOLUTION: First, the gasoline tank should be emptied, and then it should be filled with the appropriate fuel.

6. An insufficient amount of engine oil or the wrong kind in a Cub Cadet string trimmer (4-Cycle Engine)

If you own a Cub Cadet string trimmer that has a 4-cycle engine, the engine oil and gasoline ports will be located at separate fill ports on the machine.

While working with this particular sort of engine, you will not combine the gasoline and the oil. It is essential to use the appropriate quantity of engine oil as well as the suitable kind of engine oil.

Never put 2-cycle engine oil in a Cub Cadet string trimmer designed for a 4-cycle engine. While using the string trimmer, Cub Cadet suggests using motor oil with an SAE 30 rating. This engine oil manufactured by Kawasaki performs well.

To properly lubricate the moving parts of the engine, you need to use oil. If you use the incorrect kind of oil or not enough of it, friction will build up in the engine, which will cause it to overheat, which will prevent the string trimmer from starting and may permanently damage the engine.

SOLUTION: Remove the old oil from the engine, then replace it with the appropriate quality of oil. While using your trimmer in very cold or extremely hot conditions, you may need to change the viscosity so that it corresponds to the temperature of the surrounding environment.

If the issue persists, have a technician that specializes in repairs for small engines analyze the problem and decide whether or not it can be fixed in a way that is economical.

Oil for the Engine of a Cub Cadet 4-Cycle String Trimmer

Cub CadetSAE 30
Oil for the Engine of a Cub Cadet 4-Cycle String Trimmer

7. Using Outdated Gasoline in a Cub Cadet String Trimmer

If you leave stale gasoline in a Cub Cadet string trimmer, it will not only reduce the amount of fuel available, but it will also cause the carburetor and the engine to get damaged. As soon as thirty days after purchasing, gasoline may start to deteriorate and lose its quality.

Most gasoline contains ethanol, which is a component that draws moisture from the surrounding air. This moisture and ethanol combination causes corrosion in the components of the fuel system and causes the system to get gummed up.

Since gasoline may start to get stale as soon as 30 days after it has been purchased, the fuel has to be used up within this window of time. If you are unable to utilize it within this period of time, you should add a fuel additive to stabilize the fuel in order to increase the length of time it may be stored.

Always be sure you use unleaded gasoline that has a minimum octane rating of 89 (which is considered to be mid-grade) and a maximum ethanol level of 10% (E10). Never put E15 or E85 in the engine since doing so may cause damage to the engine and will likely invalidate any warranties provided by the manufacturer.

SOLUTION: When you have used all of the gasoline that is currently in your string trimmer, you should refill it with new fuel. A mixture of gas and fuel with a ratio of 40:1 is necessary for a two-cycle engine. A 4-cycle engine needs straight gas.

To stabilize the gasoline and minimize the amount of moisture that is present in the fuel, use a fuel stabilizer such as Sea Foam Motor Treatment or STA-BIL.

8. A String Trimmer from Cub Cadet Suffering from a Defective Primer Bulb

If the priming bulb on your Cub Cadet string trimmer is broken and won’t allow gasoline to fill it, it won’t work properly to provide fuel to the carburetor, which prevents the string trimmer from starting.

SOLUTION: Check to see that the gasoline line is hooked to the priming bulb in a safe and secure manner. In the event that the gasoline bulb is damaged, replace it with a new priming bulb.

9. A Cub Cadet String Trimmer Suffering from a Blocked Fuel Line

As fuel becomes old and stays in your string trimmer for a while, it might leave behind sticky deposits that block fuel flow. This may cause the gasoline line to get clogged, which will prevent the engine from starting.

SOLUTION: If the fuel line on your Cub Cadet string trimmer has broken, kinked, or become blocked, you will need to replace it.

10. The Cub Cadet String Trimmer’s Fuel Tank Vent Was Blocked With A Plug

It is possible that the fuel tank vent may be integrated into the gasoline cap or will be coupled to a line that extends from the fuel tank. It is impossible for air to enter the gasoline tank through the tank vent if this component gets clogged and stops functioning properly, which prevents air from entering the fuel tank.

When the gasoline tank loses its ability to vent, a vacuum will create within the tank, which will prevent fuel from leaving the tank and going to the carburetor. If there isn’t enough gasoline getting into the carburetor, the trimmer won’t start.

If you are unable to start your string trimmer unless you remove or loosen the fuel cap in order to let air into the fuel tank, this is a solid sign that you may have a problem with the vent on the fuel tank.

If it does start, you may verify that the problem is with the gasoline tank vent by putting the trimmer through its paces with the fuel lid well closed. Watch to see if the engine turns off and refuses to start again until the fuel cap is loosened.

SOLUTION: It is necessary to replace the fuel tank vent in order to allow air to enter the fuel tank.

11. The carburetor of a Cub Cadet string trimmer was covered with dirt and debris

Prior to the beginning of the combustion process, the carburetor is in charge of regulating the amount of gasoline that is mixed in with the air that is contained inside the cylinder. If the gas in your trimmer has been sitting for a long without being used, it is not unusual for the carburetor to get clogged with old gasoline and for fuel routes to become blocked.

In the event that this happens to your Cub Cadet, in order to get the machine started once again, you will need to either clean the carburetor or replace it with a new one.

SOLUTION: If you have any mechanical ability, you should have no problem taking care of the cleaning of your carburetor. Carburetor cleanser should be used after the device has been disassembled and reassembled in order to be cleaned.

If, after being cleaned, the carburetor still does not perform properly, you will either need to repair it or buy a new carburetor to replace it.

It may be more cost effective for you to purchase a brand new string trimmer from Cub Cadet, depending on the kind of string trimmer you use and the cost of a carburetor, as opposed to spending money to replace the carburetor on an older trimmer.

You should compare the cost, age, and model of your present Cub Cadet to a new string trimmer before making a purchase.

12. A String Trimmer from Cub Cadet Suffering from a Defective Recoil Starter

The engine of your Cub Cadet string trimmer is started by pulling a recoil starter trigger. A malfunctioning pulley, a spring that is either too loose or missing entirely, or damaged clips might prevent your recoil from functioning properly.

SOLUTION: You have the option of replacing the spring and restringing the recoil mechanism.

If it does not function because other components in your recoil, such as the clips or the pulley, are broken, it is best to simply replace the recoil assembly rather than trying to repair the individual components.

13. A Spark Arrestor that Has Been Connected Into a Cub Cadet String Trimmer

A Cub Cadet string trimmer that also has a catalytic converter will be equipped with a spark arrestor as standard equipment. A spark arrestor is a tiny screen that is installed on a Cub Cadet to prevent hot exhaust material from blasting out of the machine and creating an accident or a fire.

It’s possible for the screen to become clogged up with soot, which will prevent hot exhaust air from escaping the trimmer. This may prevent a Cub Cadet trimmer from starting up properly.

SOLUTION: Ensure that the spark plug boot is disconnected. Check to see that the engine is not too hot. Take off the engine cover as well as the lid for the engine exhaust.

Take out the spark arrestor, clean it with a wire brush, and then put it back in place to get rid of the soot. If you are unable to clean it well, if it has a hole in it, or if it is damaged in any way, you will need to replace the spark arrestor screen with a new one.

14. Flooded Cub Cadet String Trimmer

It’s possible that you flooded the engine when you were trying to start it, and now it won’t turn over. This is not a really major issue, and it can be resolved very quickly.

It is possible for the Cub Cadet engine to flood if the choke is set to the closed position and the starting rope has been pulled a number of times, which allows an excessive amount of gas to enter the carburetor.

In addition, it is possible for it to occur with the switch off and the starting rope being pulled several times, as well as when the priming bulb is pressed an excessive number of times.

SOLUTION: Follow the steps below to “unflood” your string trimmer and ensure that the engine receives the ideal ratio of gasoline to air that is necessary for it to start and continue operating.

How to Repair a Cub Cadet String Trimmer with a 2-Cycle Engine That Has Been Submerged in Water

  • Check to verify that the on position of the on/off switch is selected. On many models of Cub Cadet string trimmers, this switch comes pre-positioned in the “on” position.
  • Adjust the choke lever so that it is in the open position (run). On various Cub Cadet trimmers, this corresponds to position “3.”
  • While simultaneously pulling the starting rope repeatedly, you should press the throttle trigger. The number of pulls required to get this going might range anywhere from 5 to 15. The engine of your string trimmer will start to splutter initially. Keep pulling it and give it a couple more tries; it ought to start now.