Detroit Diesel Unit Injectors and Unit Pumps

The function of the fuel system is to store and supply fuel to the combustion chamber. The major parts of the diesel fuel system are the fuel tank, fuel filters, fuel pump, electronic control module, injection nozzles or injectors, and fuel lines.

Detroit Diesel Unit Injectors There are differences between the Series 50/60 and the MBE fuel injection system. In the Series 50/60 engines, the unit injectors pressurize the fuel prior to injection. See Figure 1-1. The MBE engines have a unit pump for each cylinder that produces the pressure and a high-pressure fuel line that carries fuel to the injector nozzles.

Detroit Diesel Unit Pumps In the Series 50/60 engines, the fuel pump draws the fuel from the tank through low-pressure fuel lines leading to the water separator (not all diesel engines have a water separator). In most diesel engines, the fuel passes through a primary fuel filter before reaching the pump. The pump circulates an excess supply of fuel through the injectors, which purges air from the fuel system and also cools and lubricates the injectors. The unused portion of fuel returns to the fuel tank by means of the fuel return line.

Detroit Diesel Unit Injectors Manual The primary filter captures large contaminants from the fuel and acts as a water separator. Water is heavier than diesel fuel and falls to the bottom of the primary filter, where in most applications it can be drained. After passing through the pump, the fuel goes through a secondary filter before reaching the fuel injectors to keep them clean and prevent them free from damage. The fuel flows to the fuel injectors where it is injected into the cylinders.

Detroit Diesel Unit Pumps Manual The primary job of the entire fuel system is to inject a controlled amount of atomized fuel into each engine cylinder at the precise time. Excess fuel exits at the rear of the cylinder head just above the inlet, through a restrictive return fitting that maintains fuel pressure in the system. It then returns back to the tank.

Detroit Diesel Unit Injectors and Unit Pumps Tecnhician's Guide

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