The fuel system (Figs. I and 2) consists of the fuel injectors, fuel pipes, fuel manifolds (integral with the cylinder head),
fuel pump, fuel strainer, fuel filter and the necessary connecting fuel lines.
On In-line engines, a restricted fitting is located in the cylinder head fuel return manifold outlet to maintain pressure
within the fuel system. On V-type engines, this restricted fitting is located in the left-bank cylinder head.
Fuel is drawn from the supply tank through the fuel strainer and enters the fuel pump at the inlet side. Upon leaving the
pump under pressure, the fuel is forced through the fuel filter and into the fuel inlet manifold where it passes through fuel
pipes into the inlet side of each fuel injector. The fuel is filtered through elements in the injectors and atomized through
small spray tip orifices into the combustion chamber. Surplus fuel, returning from the injectors, passes through the fuel
return manifold and connecting fuel lines back to the fuel tank.
The continuous flow of fuel through the injectors helps to cool the injectors and remove air from the fuel system. A check
valve may be installed between the fuel strainer and the source of supply as optional equipment to prevent fuel drain
back when the engine is not running.
The fuel injector combines in a single unit all of the parts necessary to provide complete and independent fuel injection at
each cylinder. The injector creates the high pressure necessary for fuel injection, meters the proper amount of fuel,
atomizes the fuel and times the injection into the combustion chamber.
Since the injector is one of the most important and carefully constructed parts of the engine, it is recommended that the
engine operator replace the injector as an assembly if it is not operating properly. Authorized Detroit Diesel Allison
Service Outlets are properly equipped to service injectors.
Fig. 2. Schematic Diagram of Typical Fuel System - V-
Fig. 1. Schematic Diagram of Typical Fuel
System - In-Line Engine