Mercedes Diesel Engine Parts & Injectors

In a petrol Mercedes engine a mixture of petrol and air is ignited by an electric spark from the spark-plug; but a Mercedes diesel engine has no spark plugs. Another essential difference is that Mercedes diesel engines use a different type of fuel – gas oil.
Ignition in a Mercedes diesel engine is caused by compression, which raises the temperature of air in the combustion chamber above the flash point, or self-ignition temperature, of the fuel.
Diesel fuel, less easily evaporated than petrol, is not drawn in with air as a mixture, but is sprayed under high pressure from an injector into the combustion chamber, where it ignites on contact with the hot, and compressed air. Each Mercedes diesel injector is supplied with fuel in metered quantities and at a high pressure by a Mercedes engine-driven pump. The accelerator controls the amount of fuel delivered by the pump, and hence the power delivered by the engine.
The Mercedes diesel engine advantages lie in its greater efficiency (resulting in lower fuel costs), longer life and lower maintenance costs.
Its disadvantages include a high initial cost, greater weight, a somewhat rougher idling, some smell, a higher noise level and slower acceleration.
In a medium sized Mercedes, gas is compressed to about one-ninth of its original volume, giving a compression ratio of 9:1; in a Mercedes diesel engine it may be as high as 22:1; to increase the temperature of the air to the flash-point temperature of the diesel fuel.
A Mercedes diesel engine has a much smaller combustion chamber than a petrol engine, and its higher compression ratio results in greater efficiency, because more potential heat-energy is converted into power and less heat is wasted.
To ensure the correct amount of fuel is injected at the right moment, each cylinder on a Mercedes diesel engine is fitted with an injector. A pump, driven at half the crankshaft speed, forces fuel into the combustion cylinders in their firing order.
In the diesel 4-stroke cycle, pure air is drawn into the cylinder on the suction stroke; fuel is injected and starts to burn towards the end of the rising compression stroke; pressure from the expanding gases forces the piston down on its powers stroke; and burnt gases escape as the piston rises on its exhaust stroke.
In some Mercedes diesel engines, a heater plug is fitted to help starting at low temperatures. This does not produce a spark but glows continuously until air temperature in the engine cylinders is high enough to ensure self-ignition of the fuel sprayed into the combustion chamber.