Diesel Engine Fuel System

A diesel engine fuel system consist of a fuel tank, fuel-water separator, fuel feed pump, fuel filter, fuel injection pump, fuel injector, low and high-pressure fuel lines,etc.

Fuel supply flow:

Fuel tank—fuel-water separator—fuel feed pump—fuel filter—fuel injection pump—fuel injector

Fuel return flow:

Injector return line—fuel return house—fuel tank

The function of fuel feed pump is to deliver fuel from the tank to the fuel injection pump. From the injection pump the fuel is fed through the high-pressure line to nozzles of the fuel injectors. The fuel atomized by the nozzles is injected into the cylinders according to the engine firing order. Surplus fuel is returned from the fuel injection pump and nozzles to the fuel tank. The air is supplied to the cylinders through the air cleaner.

The fuel injection pump injects fuel under high pressure to the engine cylinders in a particular sequence. The injector pump is driven from the camshaft by means of a gear train. The pump comprises a body, a camshaft, the sections ( according to the number of cylinders), and a plunger control mechanism.

A section of the injector pump consists of a plunger and a barrel, a roller tappet,and a delivery valve. 

To pressurize the fuel, the plunger moves up or down, and the distribution shaft rotates with the revolution of the camshaft to distribute the fuel to the cylinders individually.

Specifically, one revolution of camshaft completes four cycles, including switching over to the high pressure flow path to each cylinder with the distribution shaft, opening delivery valve, high pressure pipe, fuel injection valve" , and engine cylinders in this order. This process is repeated by the revolution of the camshaft.

Fuel system has automatic air bleeding system.