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What Causes the Kohler Engine to Lose Power Under Load?

Whenever you see high-build machinery cutting grass, chomping up dirt, or blowing leaves, there is a high possibility that it’s powered by a Kohler engine. A Kohler engine is used in all sorts of consumer and commercial devices like generators, lawnmowers, portable welders, and power washers.

Many reasons cause the Kohler engine to lose power under load. The problem can range from the dirty fuel line to faulty spark plugs to incorrect oil levels. Before taking your machine to a service center, you should try to solve the problem first.

What Causes the Kohler Engine to Lose Power Under Load

What Causes the Kohler Engine to Lose Power Under Load

Kohler engines are considered to be one of the best engines in the market. Yet problems can and will occur. So it’s important to know the troubleshooting process. Also, knowing the position of various components will save you time and money.

There can be many reasons for your engine to lose power. To identify the causes, you may have to take your machine apart. 

The following tools will help you in the process:

  • Screwdriver
  • Work gloves
  • Protective glasses
  • Rags
  • Pliers
  • Socket wrench set
  • Spark plug socket
  • Adjustable wrench
  • Multimeter
  • Wire brush
  • Box / open-end wrenches

Here is a list of few factors that makes your engine lack the power that it once had:

Inadequate/Wrong Fuel

This factor is often overlooked although it’s pretty basic. Adequate and the right kind of fuel is a must for a healthy engine. 

You must check if you have adequate fuel. If there is wrong fuel in the tank make sure to drain it. In case there is a quarter of wrong fuel, top it off with the right one.

Inadequate/Wrong Fuel

Old Gas in the Tank

If your engine is old, it can have old gas in the tank. Fuel in the last few years now may consist of up to 10% ethanol. As a result, it attracts debris and moisture that reduces the fuel quality. This can cause the engine to function poorly. 

You should drain the fuel tank and carburetor in this case.

Faults in Fuel Line

Once you have checked the fuel level, check the fuel line for dirt, clogs, or leaks. You must switch off the machine before removing the fuel line from the tank. Clean the dirt and look for possible leaking and hairline cracks. 

If your machine works with a fuel pump, check for dirt and cracks. Brittle and worn-out internal parts mean you have to buy another pump. You must clean your fuel filter and check for damage.

Faulty Spark Plugs

Spark plugs in the engine can be damaged, corroded, or fouled. 

It is always recommended to replace spark plugs at a regular interval. To avoid debris, clean the area around the spark plug lead after disconnecting it. Use a spark plug socket to detach the spark plug and clean the area. You can use a wire brush for cleaning.

If you find the spark plug wet, the problem could be water in fuel or a malfunction in the choke system. But if it is dry, the problem could be a clogged carburetor needle or a leaking carburetor mounting gasket. If there is any sign of cracks or burns, replace your spark plug. Never over-tighten a spark plug.

Dirty Air Filter

Before getting into the carburetor, air goes through a filter that catches dust and debris. If the air filter is dirty, it can cause the engine to sputter irregularly and die. You should replace air filters every season. 

If it is a foam filter, clean out the filter with detergent and hot water. Let it dry thoroughly before installing it. But if the filter has pleated paper, you have to replace it immediately. 

Dirty Air Filter

Inaccurate Oil Level

New and fresh oil is clear and amber in color. On the other hand, dirty oil is dark in color. Dark oil means it isn’t that good at protecting the engine like before and it can also damage internal engine components. You have to replace the oil. 

Now that you have determined the freshness of the oil, check if it’s at the proper level. The oil level should be between the two holes of your engine dipstick. Under or over the required level is as bad as dirty and old oil. It can ruin your engine.

Dead Battery

You should check the battery and battery terminals. Your battery can lose its charge if it’s unused for a long time. Revive your battery by charging it for few hours. You can use a multimeter to check for a dead battery.

Dead Battery

Unclean Choke

When you start your machine, the choke opens, and therefore, gasoline and air move in your carburetor. If the choke is covered with dirt and oil, it will not open. So, your machine will function poorly and eventually shut off. 

Make sure that you wipe the choke and its surroundings and get rid of the stickiness. You can use the spray carburetor clean for better results. Now when you turn it back on, the dirt will be removed with movement.

Moreover, when the choke connections are not properly aligned and loose, the choke will not open. And thus, you get a dead engine.

Unclean Choke

Flaws in Electrical Circuits

Use a voltmeter/multimeter to check and test the electrical circuitry. Check if the circuits have electrical flow.

Flaws in Electrical Circuits

Malfunction in Carburetor

The carburetor of your engine may need to be replaced, rebuilt, or cleaned. Fixing it requires more effort and time as it’s a more involved process. Before trying to fix it, you must clean it and its components first. However, purchasing a new carburetor is cheaper than rebuilding the kit.

Moreover, the choke lever of the carburetor may be closed or partially closed. It can hinder the performance of your engine. 

Malfunction in Carburetor

Other Reasons

The valves or the piston rings of your engine may have improper sealing. The ignition time of the engine can be off. Also, the head gasket can be damaged or the cylinder head can be loose. This happens when the engine runs low on oil or is overheated.


How Can I Maintain the Kohler Engine?

These maintenance tips will keep your engine in tiptop shape:

  • Read up on the manual
  • Keep it clean after every use
  • Check the filters and oil regularly
  • Examine and replace the spark plugs, if necessary
  • Adjust loose connections
  • Sharpen dull blades

What Fuel Should I Use in My Kohler Engine?

It is recommended to use gasoline or diesel in the Kohler engine. Gasoline fuels with methanol blends and higher concentrations should be used in the engine. The diesel fuels that are used in cars should be used here. Avoid dirty diesel fuel as it can cause serious engine faults.


A healthy engine will provide you with more power out of the engine. Kohler engines are proven to last longer and are better balanced compared to other brands. No matter how good they are, you need to maintain your engine and check on the components of it. Because a fault in the components can eventually cause the Kohler engine to lose power under load. With proper maintenance and care, your Kohler engine will last longer.

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