By: Chief Mike Kull

Power tools can increase the ability of firefighters to perform their required tasks at emergency incidents and help to protect lives and property. Your petrol powered tools must be properly maintained. They must be started and run until the engine is warm on a regular basis. There will be times that you will not be able to get the engine started. Here are some basics to check when troubleshooting an engine that will not start.

Petrol powered equipment is very similar to the fires that we fight.  A fire requires three things in order to burn: Heat, Fuel and Oxygen.  In the same way, a petrol engine requires those same three things: Spark (Heat), Petrol (Fuel) and Air (Oxygen).  If a petrol engine will not run the first steps to fixing it requires checking those three things.

Spark (Heat):

The first thing to check is if the engine has spark.  To check this, you must remove the spark plug.  A look at the spark plug will tell you something about the engine’s performance.  If the spark plug is wet and black, there may be too much fuel (Rich).  If the spark plug is brown, there may be too much air (Lean).  Clean and dry the spark plug and check the gap of the electrode.  The correct gap is usually about the thickness of a thin coin.  After cleaning and setting the gap, be sure the top of the spark plug is firmly set into the spark plug wire and hold the bottom metal end of the spark plug against the metal of the engine block.  Pull the starting rope of the engine and watch to see if the plug is generating a spark.  If not try cleaning and resetting the gap.  If it still does not spark, replace the plug.  If there is still no spark, this indicates a bigger problem with the engine than we are discussing in this post.  If there is a spark, it is time to move on to the next item to check.

Fuel (Petrol):

The first thing to check is how fresh the fuel is.  It is always a good idea to empty the fuel tank and replace with freshly purchased fuel.  While the fuel tank is empty, look to see if it contains any dirt or debris and clean the tank if necessary.  Next, it is important to check the fuel filter.  Some small engines may not have a fuel filter.  If there is a fuel filter, look at it’s condition.  Is it filled with dirt and debris?  Can the fuel flow through the filter?  If not, the fuel filter must be replaced.  If installing a new fuel filter, be sure to check if there is an arrow indicating the correct direction of fuel flow and install properly.  It is also important to check the condition of the fuel lines (hoses) to make sure there are no leaks or clogs.  A final, more advanced component to check is the carburetor.  Many times, an engine that has not run for a while will have varnish or clogs in the carburetor blocking the fuel jets and preventing fuel from flowing through the carburetor.  If you disassemble the carburetor, be careful not to damage any gaskets and count the number of turns that it takes to remove any components so that you can return them to the same settings when you reassemble.  Also check that the floats inside the carburetor can move freely and are not filled with fuel.

Air (Oxygen):

The final component required for an engine to run is air.  Check the air filter.  You should be able to see a light shining through the air filter.  If the filter is covered in dirt and debris, clean the filter by gently brushing it off, being careful not to damage the filter material.  If necessary, replace the filter.  If the air filter is made of foam and you can not purchase a replacement filter, you may be able to make a new one.  Foam can be cut to the size of the original to use if necessary.  Be sure that the foam is not too dense to allow air to flow through.  Also be sure that the foam you use is not falling apart, allowing pieces of the filter to be drawn into the engine.  The other item to check with air is the choke.  Be sure that the choke lever is connected and working properly to restrict the flow of air when starting a cold engine and opens to allow in more air when the engine is running.

Starting the Engine:

When attempting to start a cold engine, be sure to fully close the choke.  Set the engine’s throttle to the starting position and pull the starting rope.  As soon as you hear the engine try to start or sputter, open the choke.  The engine should start in the next few pulls.

Flooded Engine:

Sometimes when an engine will not start it is because the engine has gotten too much fuel (flooded).  This happens when the choke is left on after the engine first begins to fire.  There are two ways to tell if the engine is flooded.  The first is if you smell petrol.  A flooded engine will have a strong smell of petrol.  The second way to check for a flooded engine is to remove and examine the spark plug.  If the spark plug is wet with petrol, it is most likely flooded.  Dry the plug and try again.  

If the engine does get flooded, it can usually be started by opening the choke fully, opening the throttle all the way and pulling the starter rope until the engine starts.  (This may take many, many pulls.)  Sometimes a flooded engine can be started after sitting for a few hours to allow the excess fuel to evaporate.

Other Simple Causes:

There are two other simple things that should not be overlooked.  If the engine has an On/Off Switch, be sure the switch is set to the On position.  Second, some petrol engine’s have a low oil shut off switch.  Ensure that the engine has the proper amount of oil.

These were some of the most common causes of problems found in petrol powered engines and a quick overview of how to begin to get an engine running.  Proper care and maintenance of an engine will prevent many of these problems in the future. 

About the Author:

Chief Mike Kull has been serving his local community in rural Pennsylvania for 25 years. Chief Kull serves as Fire Chief and Administrator of his local volunteer fire department as well as serving as a local elected official and has served in various government roles for his entire career. He is also a Forest Fire Warden with the PA Bureau of Forestry and serves on his church council.