Fuel Supply

Fig. 5 Diesel fuel system:

Fuel is drawn through the filter from the tank by the injection pump, Fig. 5. The injection pump meters and distributes fuel under pressure to the injectors in the correct firing order.
Excess fuel from the pump and injectors returns to the tank through a separate line.
The fuel circulation cools and lubricates the injection pump and injectors and also warms the fuel in the tank slightly to help prevent wax formation during cold weather.