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TM 10-3930-671-24
5.3. Diesel Fuel Injection System
TMD27 (2.7L) Diesel Engine
Description and Operation .............................................................................................................. F-199
Engine Fuel Lines ........................................................................................................................... F-200
Fuel Injection................................................................................................................................... F-202
Fuel Supply (Transfer) Pump .......................................................................................................... F-203
Fuel Pump Troubleshooting ............................................................................................................ F-203
Priming The Fuel System................................................................................................................ F-203
Fuel Filters ...................................................................................................................................... F-204
Fuel Filter Replacement .................................................................................................................. F-204
Fuel Injectors................................................................................................................................... F-204
Fuel Injector Testing........................................................................................................................ F-205
Injection Pump ................................................................................................................................ F-206
Injection Pump Overhaul................................................................................................................. F-206
Timing Of Injection Pump To The Engine ....................................................................................... F-206
Reinstalling & Timing the Original Fuel Injection Pump .................................................................. F-207
Installation & Timing A New Fuel Injection Pump ........................................................................... F-208
Fuel Recommendations .................................................................................................................. F-208
Diesel Fuel Specifications ............................................................................................................... F-208
Description and Operation
The basic function of the diesel fuel system is to store,
deliver, and inject fuel into the engine.
The fuel injection system of a diesel engine includes a
fuel supply pump, fuel filters, an injection pump assembly
complete
with
governor,
high-pressure
steel
lines
connecting the pump discharge outlets to the injector
nozzles, and nozzle holders and nozzle assemblies, one
for each cylinder.
The electric fuel transfer (supply) pump draws the fuel
from the fuel tank, forces it through the filters, and
delivers it to the injection pump. The fuel injection pump
places it under the high pressure required for mechanical
atomization, precisely meters the fuel, and distributes it
in the proper timing sequence to the nozzles which
produce the correct uniform pattern of spray for the
combustion chambers.
The fuel filter elements play a key part in the injection
system, since fine particles of dirt in the fuel are
extremely destructive to all high-pressure pumps.
Careless or too-frequent removal of elements of the fuel
injection system for "inspection" or "cleaning" is generally
far more harmful than beneficial, due to the danger that
dirt will enter the exposed connections
and the possibility of mishandling of parts. Various
components are made with the utmost precision and
may be easily damaged when removed. Unnecessary
entry into the fuel system could cause needless service.
It should be kept in mind that minor troubles, such as
suction leaks at joints in the supply line, can cause poor
or erratic performance. It is unlikely that the injection
pump would require service or overhaul before several
thousand hours of operation.
NOTE
There should be no tampering with
the injection pump assembly, or
removal of It for Inspection, unless
engine
operation
Is
seriously
Impaired
and
the
cause
of
the
difficulty Is directly traceable to the
pump unit.
F-199
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