Komatsu 114E-3 Series Shop Manual page 82

SEN00176-02 10 Structure, function and maintenance standard
A lift pump is used for priming the pump at start-up.
The lift pump runs for approximately 30 seconds
after key on. Once the engine is started, the gear
pump is able to maintain prime without any assis-
tance from the lift pump.
The ECM and ECM cooling plate must be removed
for access to the lift pump and lift pump fuel lines.
This is accomplished by disconnecting the engine
harnesses and the quick disconnect style fuel lines
first. Removal of the ECM cooling plate capscrews
allows the ECM, cooling plate, lift pump and lift
pump plumbing to be removed as one assembly.
The gear pump output is routed to a 2-micron fuel
filter. The filtered fuel returns to the fuel pump actu-
ator housing.
The high-pressure pump is driven by the engine
camshaft. The gear pump is driven by the pump
camshaft through an internal coupling.
Each of the two pumping plungers is driven by a
three lobed camshaft. The camshaft is located in
the cam housing module by tapered roller bearings.
The bearings that support the camshaft, as well as
the tappets, rollers and camshaft itself are lubri-
cated with engine oil. These are the only compo-
nents in the pump lubricated with engine oil.
Engine oil to the high-pressure pump is supplied
through a drilling in the engine gear housing. The
oil passes from the engine gear housing to the
high-pressure pump cam housing. A small O-ring in
a recess on the back of the engine gear housing is
used to seal this passage.
Pressurized fuel from the gear pump is supplied to
the fuel pump actuator. The fuel pump actuator is
opened or closed by the ECM to maintain the
appropriate fuel rail pressure.
An air-bleed orifice fitting in the fuel pump actuator
housing aids in purging air from the fuel supply.
Because of the air-bleed orifice fitting, some fuel
that is supplied by the gear pump will return to drain
at all times.
12
114E-3 Series