Four systems are necessary for proper operation of the internal combustion engine: fuel, ignition, lubrication and cooling systems.

The Fuel System. 

The gasoline engine fuel system must supply the engine with a mixture of air and fuel that burns within the cylinders. Gasoline engines use a carburetor mixing the fuel and air and delivering the mixture to the engine through the intake manifold. Air-fuel rations vary for idling, light and heavy-load operations. Diesel engines have a high-pressure pump forcing the fuel through injectors into the combustion chamber.

The Ignition System. 

In gasoline engines the fuel charge is ignited by an electric spark. These are spark ignition engines. In diesel engines the compressed air ig­nites the fuel charge. Diesels are compression ignition engines.

Spark ignition engines use an electric ignition system providing the ignition of the fuel charge. Two types of electric ignition systems are commonly used: the battery system and the magneto system.

The Lubricating System. 

A film of oil is produced between the working surfaces of the metal parts. In this way friction and wear are being reduced because the film of oil keeps the surfaces apart.

 A lubricating system is necessary in order to deliver the oil to the moving parts of the engine. All modern tractor engines are lubricated by the force-feed method. Engine lubrication is provided by an oil pump located in the oil pan. Gear-type pump are commonly used in most engines because of their long life and trouble-free operation.