The V-71 Detroit Diesel engines incorporate four
A brief description of each of these systems and their
basic systems which direct the flow of fuel, air,
components, and the necessary maintenance and
lubricating oil, and engine coolant.
adjustment procedures, are given in this manual.
The fuel system (Fig. 1) consists of the fuel injectors,
fuel pipes, fuel pump, fuel strainer, fuel filter and the
necessary connecting fuel lines.
An injector may be removed in the following manner:
1. Remove the valve rocker cover.
A restricted fitting is located in the outlet passage in
one of the cylinder heads on 6, 8 and 12V engines to
2. Disconnect the fuel pipes from both the injector and
maintain pressure in the fuel system. Two of the
the fuel connectors.
cylinder heads on 16V engines have a restricted fitting.
3. Immediately after removing the fuel pipes, cover
the injector inlet and outlet fittings with shipping caps
Fuel is drawn from the supply tank through the fuel
to prevent dirt from entering.
strainer and enters the fuel pump at the inlet side.
Upon leaving the pump under pressure, the fuel is
4. Turn the crankshaft manually in the direction of
forced through the fuel filter and into the fuel inlet
engine rotation or crank the engine with the starting
manifold where it passes through fuel pipes into the
motor, if necessary, until the rocker arms for the
inlet side of each fuel injector. The fuel is filtered
particular cylinder are aligned in a horizontal plane.
through elements in the injectors and atomized
through small spray tip orifices into the combustion
chamber. Surplus fuel, returning from the injectors,
passes through t h e 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
A check valve may be installed between the fuel
s t r a i n e r 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
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.
Fig. 1 - Schematic Diagram of Typical Fuel
Authorized Detroit Diesel Allison Service Outlets are
properly equipped to service injectors.