TM 9-2320-260-34-1
ENGINE MAINTENANCE
Section I.
Section II.
Section III.
Section IV.
Section V.
Section VI.
Section VII.
Section I. DESCRIPTION AND DATA
a. The Cummins NHC-250 diesel engine is used on all M809 series vehicles. It is a naturally-aspirated,
liquid cooled, overhead valve, four-cycle engine of in-line, six-cylinder design. The NHC-250 engine has a
compression ratio of 15.8 to 1 and develops 240 horsepower at 2100 rpm. Peak torque is 560 lb-ft. at 1600 rpm.
b. Both early model engines, before serial number 1124663, and late model engines, after serial number
1124663, are covered in this chapter. The differences between early and late models are changes to make the
clean air configuration and the use of top stop fuel injectors. Changes to the clean air configuration provide
for controlled engine exhaust gas recirculation back to the air intake manifold. The top stop fuel injectors
are different from early model engine injectors in that the adapter is lower to accommodate the stop. The
plunger coupling top is smaller and has an adjustable stop screw and locknut. Further description and
data on fuel injectors can be found in chapter 4 of this manual.