Overview of the internal combustion engine

Problem solving for diesel engines.
Useful information.
Overview of the internal combustion engine.
To be able to carry out any form of fault diagnosis, and maybe even an emergency repair, it is of great advantage if you are first acquainted with the general principals of the internal combustion engine. You do not, on the other hand, need to know all of the technical details just to have an overview of the workings in your minds eye.
A few basic principals of the workings of a diesel engine, for example, apply to diesel cars, trucks, generators and large marine engines. Yes they are all the same but they have different components of different sizes and usually placed in slightly different positions. The working principal, though, still remains the same.
To simplify matters we are going to deal with what takes place in just one cylinder of a gasoline engine and one cylinder of diesel engines through their full running cycle. The same principals will apply regardless of how many cylinders are actually used in a particular engine.
Also we are only going to discuss the four-stroke cycle (fully explained in the later text) for diesels and gasoline engines. There is also the two stroke cycle in use, but it is only generally found in use in smaller capacity engines (such as some small generators, chain saws, outboard motors and some small motor cycles).
First of all, and probably most important, what exactly is meant by the term Internal Combustion Engine?
Simply put it means the burning of a flammable substance (fuel) inside the engine, the substance in this case being either Diesel Oil or Gasoline (petrol). This burning of the fuel is where these engines derive their power from and just how it transpires is dealt with in the following sections under the headings Gasoline Engines and Diesel Engines.
Secondly, what exactly is meant by the term FOUR-STROKE cycle ?
To derive it's power from the heat of the burning fuel the four stroke engine (whether diesel or gasoline) has to complete four separate cycles. The completion of four piston cycles takes 2 complete crankshaft revolutions. These cycles are explained in greater detail, (together with the aid of sketches), in the next two sections of this work, but briefly, look below for a brief overview.
Induction
Intake (suction) of air alone (in a diesel engine), or, air and gasoline vapour in a gasoline engine.
Compression
Compressing of the above gases.
This completes the first revolution of the crankshaft.
POWER
Igniting of the compressed gasoline vapour by a spark within a gasoline engine, or, the injection of a diesel mist through an injector, which then self ignites due to the heat, generated by compressing the air. This produces a rapid expansion and therefore power.
EXHAUST
The blowing out of the spent gases. And then the process starts all over. This completes the second revolution of the crankshaft.
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