An internal combustion engine has an ignition system which would depend on the type of engine and fuel used of the unit. In the case of petrol engines, these are usually ignited by a precise and timed spark, while diesel engines by are ignited by compression heating.
With a controlled and precise of a mixture of an electric spark from a spark plug, the mixture would create an ignition in a spark ignition engine. While this is the ignition type for almost all gasoline engines, the timing on the other hand for diesel engines is through a precise and controlled pressure pump and injector.
Ignition happens when the temperature of the fuel/air mixture is taken over by the autoignition temperature because there is heat generated during the compression stroke of which air is compressed. Note that the biggest number of compression ignition engines are those of diesels where the fuel is mixed with the air after reaching ignition temperature.
Note that fuels burn faster and more efficiently when there is a large representation of surface area to the oxygen in air. The traditional way to atomize liquid fuels, which is needed to create a fuel air mixture, is to have it done with a carburetor in petrol engines and with the fuel injection in diesel engines. Although the technology is quite different, many of the modern petrol engines use fuel injection also.
The supply of fuel into the cylinder of a simpler reciprocating engines would use a carburetor still. Carburetor technology in vehicles have reached a level of very high sophistication and precision, but in mid 1980s, it lost out to fuel injection in terms of cost and flexibility. Small engines like lawn mowers and small motorcycles in their more sophisticated forms, remain to use the simple forms of carburetor.
Automobiles using larger gasoline engines have moved to using fuel injection systems. In the case of diesel engines, the use of fuel injection system has been done since the timing of the injection would start and control the combustion.
Where autogas engines is concern, it uses the system of fuel injection or the open or closed loop carburetors.
Many internal combustion engines now require a fuel pump. Where diesel engines is concern, it uses an all mechanical precision pump system that produces a timed injection directly into the combustion chamber, thus requiring a high pressure of delivery so that the pressure of the combustion chamber is overcame.
For four stroke engine, it has these parts of the engine, namely the crankshaft, connecting rod, one or more camshafts and valves.