Internal Combustion Forklift Operation

Application & Operation

An engine is a device that uses chemical energy – a fuel – to produce mechanical energy. Engines operating on this principle are called internal combustion engines and are used in an internal combustion forklift.

Because automobiles use the same type of engine, many people are familiar with an internal combustion (IC) engine. While it operates similar to your vehicle, four unique engine types are used in forklifts.


  • Gasoline engines use the same fuel as an automobile.
  • Liquefied Petroleum Gas (LPG) engines run on a gas that occurs naturally. LPG is commonly used for gas grills.
  • Compressed Natural Gas (CNG) engines use the same fuel supplied to homes and businesses to power stoves, furnaces and other appliances.
  • Diesel engines use diesel fuel, a lower grade fuel not as refined as gasoline and therefore, not as      combustible.


An ignition battery and gear-driven starter forces the engine to “crank over,” starting the internal combustion process. The carburetor mixes a combustible, liquid fuel with air and injects it into the cylinders through the valve. Within the cylinder, the piston is attached to a rod, which in turn is attached to the crankshaft.

Mechanical energy is produced when the spark plug introduces a spark to the compressed fuel/air mixture, igniting the explosion. The explosion drives the piston and rod down in the cylinder. Because of the way the crankshaft is designed, it will convert the downward energy of the piston and rod to the mechanical energy (RPMs).

A series of these cylinders is connected to the crankshaft in the block. The block contains other mechanisms, like the cam shaft, which uses the RPMs to open and close the valves in precise timing sequence. This mechanical energy also drives the alternator or generator (found mounted to the engine and driven by a belt) which supplies current to the lift truck’s electrical components. Additionally, the electricity produced in this way is used to drive the power steering and lift/tilt hydraulic pumps


An IC forklift is used where power requirements are more demanding and when exhaust fumes are not a concern. It provides more lugging power for heavier loads on uneven surfaces. IC forklifts, like your car, are not affected by unpredictable weather conditions and can operate in rain or snow.

Have questions about your internal combustion forklift’s engine? Call Thompson & Johnson today to speak to an equipment specialist or fill out a Customer Request Email Form above! 

Got Questions?

If you have a question on this or any topic related to safety with your forklift, give our resident expert, Dave Bennet, a call or fill out the request form.