for injection. A bypass pressure relief valve limits the
OPERATIONS. The injection pump (fig. 5-12)
forces fuel under high pressure to the injection valves.
Injection pump plungers and lifters are actuated by lobes
on the pump camshaft and always make a full stroke.
The lifters are held against the pump camshaft by spring
pressure, applied to the plungers.
GOVERNOR. The governor on the compact fuel
system is hydraulically operated. Governor action
controls the amount of fuel injected by turning the
plunger (fig. 5-1) in the barrel through a gear segment
on the bottom of the plunger. Pressurized lubrication oil
enters the passage in the governor cylinder. The oil
encircles the sleeve within the cylinder and is directed
through a passage to operate the piston.
Lubrication oil from the governor drains into the
fuel injection pump housing.
TROUBLESHOOTING. Many times the fuel
system is blamed when the fault lies elsewhere,
especially when smokey exhaust is the problem.
Smokey exhaust can be caused by lack of air for
complete combustion, overloading, oil burning, lack of
compression, as well as faulty injection valves or
The two troubles in the compact system are lack of
fuel and too much fuel for proper combustion. If the time
dimension is too small, injection will begin early; and if
too great, injection will be late. When checking plunger
wear, check the lifter washer for wear to avoid rapid
wear of the plunger. If the plunger length is not within
limits, discard the plunger.
When the engine is started, the speed limiter plunger
restricts the governor control linkage. Operating oil
pressure has to react on the speed limiter before the
governor control can be moved to the high-idle position.
At low idle, a spring-loaded plunger bears against the
shoulder of the low-idle adjusting screw. This action
forces the plunger past the shoulder on the adjusting
screw, and stops the engine.
Figure 5-11.-Precombustion chamber and fuel injection valve.
Figure 5-12.-Compact fuel injection pump.