FUEL
SYSTEM
The diesel
fuel
system provides a
means
of
filtering,
transporting
and
delivering fuel
in a
fine
spray to the
engine cylinder at the correct time for
ignition.
The
system consists of a primary
fuel filter, fuel
transfer
pump,
secondary
fuel filter, injection
pump and an
injection
nozzle. See Figure 11.
The diaphragm
fuel
transfer pump
which
operates
direct-
ly
off the engine camshaft, draws
fuel from
a supply
tank and delivers it through two
filters
to the
injection
pump.
The
injection
pump
meters
fuel
and delivers it,
at
high
pressure
to the
injection
nozzle at the correct
time
for
ignition.
The
injection
nozzle
opens
at a set
fuel
pressure,
de-
livering fuel
in a
fine
spray, to the precombustion
chamber for
ignition.
The nozzle remains open, deliver-
ing fuel
as
long
as the
fuel
pressure
remains above
the
critical
point.
Extra
fuel
is bled off after
each
injection
cycle by a
fuel
return
line from
the nozzle. An
adapter
combines
the
leakoff fuel with
the
flow-through fuel from
the
injection
pump. A return
line
connected at this point,
returns the combined
fuel
back to the
fuel
supply tank.
AIR
CLEANER
MANIFOLD
HEATER
GLOW PLUG
CRANKCASE
BREATHER TUBE
FUEL
RETURN LINE
FUEL FILTER
SEDIMENT
BOWL
PRIMARY
FUEL FILTER
INJECTION
NOZZLE
INJECTION
PUMP
SECONDARY
FUEL FILTER
FIGURE
II.
DIESEL FUEL SYSTEM (BEGINNING
WITH SPEC
S)
Dirt
in the
fuei system
is a
diesel
, engine's worst enemy.
It is one of the
major causes
of
diesel engine failure. Even
a
tiny piece
of dirt
in the
injection system
may
stop your unit. When
opening
any
part
of the
fuel system beyond
the
second-
ary fuel filter, place
all
parts
in a pan of
clean diesel
fuel
as
they
are
removed. Before installing
new or
used
parts, flush them thoroughly
and
install while still
wet.
MAINTENANCE
,
In addition to regular service periods,
change
the
secondary
fuel filter
cartridge if the engine shows
signs of starving
from
lack of
fuel.
Remove the second-
ary
filter
by removing the large cap screw in the center
of
the
filter
cover. Use
care
when replacing the
filter
cartridge to
avoid
getting
dirt into
the
injection
pump
passages.
When
replacing or cleaning
filters,
bleed the
fuel
system. Do this by opening the air bleed screw located
on
top of the secondary
filter
removal cap screw. Oper-
ate the hand
priming
lever on the transfer pump
until
no
air
bubbles
flow from
the bleed screw hole, then
tighten
the bleed screw. Return the
priming
lever to its
original
position. See Figure 12.
IMPORTANT:
// the
transfer pump
cam
lobe
is on the
high side,
the
priming lever will
not
operate
the
pump.
Turn
the
engine
one
revolution beiore operating
the
priming lever.
FUEL
TRANSFER
PUMP
The transfer pump is located on the
left
side of the
engine. If
fuel
does
not reach the secondary
filter,
make the
following
checks before removing the pump.
1.
Check the
fuel
tank and see that the
shutoff
valve
is open.
2.
Remove the
fuel line from
the transfer pump outlet
and
work
the
priming
lever on the pump. Fuel
should
spurt out of the pump. If not, remove the
pump for repair or replacement.
Testing:
If the transfer pump delivers
fuel,
test
it
with
a
pressure
gauge
or manometer. Perform
these
tests
before removing the pump
from
the engine. Remove the
pump outlet and
install
the
pressure
gauge.
See Figure
13.
Test the valves and diaphragm by operating the primer
lever a few times and watching the
pressure.
It should
not
drop off
rapidly
after
priming
has stopped.
16
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