DETROIT DIESEL The V-71 Detroit Diesel engines incorporate four basic systems which direct the flow of fuel, air, lubricating oil, and engine coolant. components, and the necessary maintenance and adjustment procedures, are given in this manual. A brief description of each of these systems and their The fuel system (Fig. 1) consists of the fuel injectors, fuel pipes, fuel pump, fuel strainer, fuel filter and the necessary connecting fuel lines. Remove Injector An injector may be removed in the following manner: A restricted fitting is located in the outlet passage in one of the cylinder heads on 6, 8 and 12V engines to maintain pressure in the fuel system.
Two of the cylinder heads on 16V engines have a restricted fitting. 1. Remove the valve rocker cover. 2. Disconnect the fuel pipes from both the injector and the fuel connectors. 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. 3. Immediately after removing the fuel pipes, cover the injector inlet and outlet fittings with shipping caps to prevent dirt from entering. 4. Turn the crankshaft manually in the direction of engine rotation or crank the engine with the starting motor, if necessary, until the rocker arms for the particular cylinder are aligned in a horizontal plane IMPOBTAN’~: If a wrench is used on the crankshaft bolt at the front of the engine, do not turn the crankshaft in a left-hand direction of rotation as the bolt may be loosened.
Either 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. Fuel Injector 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. I Fig. 1 - Schematic Diagram of Typical Fuel System Page 13