What Is Under My Injector?

The components that are located under the Yanmar "YM Series" injector are shown below. Yanmar uses what is called "indirect Injection" where the fuel is not injected directly into the cylinders. Instead, the fuel is shot into a smaller cavity. These smaller cavities (pre-combustion chambers) are where the actual combustion explosion starts and then spreads out into the cylinder. The lower chamber (44) has a small nozzle that is pointed a specific direction and has a small roll pin in the side so that it can only be installed one way. 

Injector Retainer (48)
Holds the injector into the head

Injector (18)
Sprays the fuel into the engine

Insulator Washer (47)
Protects the injector from combustion temperatures as well as vibration. It is also what seals the injector to the head. This is a one time use seal and must be replaced after the injector is removed. 

Upper Pre-Chamber (45)
Creates the top of the pre-combustion chamber

Copper Sealing Washer (46)
Seals the pre-chamber halves together as well as seals the lower chamber to the head

Lower Pre-Chamber (44)
Creates the lower half of the pre-combustion chamber

Copper Sealing Washer (46)
Seals the pre-chamber halves together as well as seals the lower chamber to the head

Extra Credit:
The alternative style of diesel injection is, as you may have guessed, Direct Injection. In this system the diesel is sprayed directly onto the top of the piston, which often has a bowl shape cut into the piston itself. Direct injection is usually more efficient and produces more horsepower per amount of fuel but usually requires much higher injection pressures, is usually less forgiving, and potentially less long term durability... especially using machinery & materials from the era they were built (1970's). Yanmar chose direct injection for these engines because, at least at the time, it was much more reliable, simpler, and produced a quieter combustion explosion.