The first engine component of an engine which is dependent on the kind of engine and fuel used in an internal combustion engine is the ignition system. 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.
In the case of a spark ignition engine, ignition is by a mixture of an electric spark from a spark plug, the timing of which should be controlled precisely. Note that almost all engines in gasoline are of this kind, while diesel engines timing is controlled in a precise manner by the injector and pressure pump.
Because of the heat generated by the air compression during the compression stroke, there is an ignition which would happen as the fuel and air mixture temperature has taken over the autoignition temperature. Diesels composed the vast majority of compression ignition and this is because fuel is mixed with the air once the air has reached 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. The modern petrol engines nowadays use fuel injection too although there is a difference in the technology.
The supply of fuel into the cylinder of a simpler reciprocating engines would use a carburetor still. From the mid 1980s, carburetor technology in cars have attained a very high degree of precision and sophistication, but lost out on the cost and flexibility to fuel injection. Small engines though still remain to use the simple forms of carburetor, like lawn mowers and the more sophisticated forms of engines used in small motorcycles.
Vehicles that use gasoline of larger size have mostly moved to using fuel injection systems. The timing of the injection initiates and controls the combustion, and this is why diesel engines have always used fuel injection system.
Where autogas engines is concern, it is fuel injection system is used or the open closed loop carburetors.
A fuel pump is what most internal combustion engines require. In order for the combustion chamber to be overcome, in the case of diesel engines, an all mechanical precision pump system is used and this would produce a timed injection directly into the chamber for combustion.
For four stroke engine, it has these parts of the engine, namely the crankshaft, connecting rod, one or more camshafts and valves.