2
3.
is injected
into
the pre-combustion chamber
GOOD
j5:l:
POOR
where
it
atomizes and mixes with the hot com-
If compression temperatures are high enough,
the fuel-air mixture ignites. Injection continues
SPRAY
PATTERN
7
Fuel enters fuel duct and pressure chamber of
nozzle assembly. When fuel pressure overcomes
preset pressure of the adjusting spring, the pintle
is
forced upward off itsseat and a fine mist of fuel
pressed air.
SPRA~TERN
::$!>
:.
,
;,!
i':..
..!
.
.I
.
;I..
,.
w.+
%-
.._
.bO7
until the spill port clears the top of the metering
sleeve
in
the injection pump and dumps the high
pressure fuel into the sump allowing the pressure
spring to close the injector and cut off fuel
injection to the cylinder.
Do
not disturb the injector pressure
adjusting screw; it cannot be reset
without proper equipment.
Bypass fuel is returned to the tank after each injection
cycle by a return line from the nozzle.
A
fuel return
fitting combines the return fuel from the injectors
with the flow-through fuel from the injection pump
bleed valve.
A
return line connected at this point
returns the combined fuel back to the fuel supply
tank.
PRESSURE
FUEL INLET
VALVE^\^'
Z
SEAT
ADAPl
Ty
PINTLE
FIGURE
12.
INJECTOR NOZZLE AND
HOLDER ASSEMBLY
ASSEMBLY
-ER
Nozzle Spray Pattern
A
suspected nozzle can be checked in the field by
removing
it
from theengineand reconnecting
it
to the
high pressure line. The spray pattern (Figure
13)
can
be observed as the engine is cranked.
Fuel penetrafion of the skin might
causesevere personalinjury.
Do
not
let the nozzle high-pressure fuel spray against skin
surfaces.
WARN,NG
FIGURE
13.
NOZZLE SPRAY PATTERN
If streamers are visible, the pattern is badly distorted
or the nozzle drips before
it
reaches opening
pressure, it is defective and must be cleaned or
replaced.
Cleaning
is
the most important part
of
nozzle maintenance. Make
sure the work area and equipment are exceptionally clean.
A
second method for determining a misfiring nozzle
is to remove'the exhaust manifold, run the engine,
and observe the exhaust ports for the following
conditions:
Heavy Load
-
Black smokey exhaust from any one
cylinder could indicate poor nozzle condition.
Light
or
No
Load
-
Blue/white smoke from any one
cylinder could indicate poor nozzle condition.
Adjustment:
To adjust the opening pressure, remove
each nozzle from the engine. Remove the plug from
the center of the cap nut and loosen the cap nut.
Install the nozzle to be tested on a static fuel nozzle
testing fixture (may be purchased from Onan). Fol-
lowing the instructions on the tester, adjust the open-
ing pressure to
1750
psi
(12,075
kPa) by turning the
adjusting screw. Clockwise increases the pressure
and counterclockwise decreases
it.
Do
not try to
adjust the pressure without a testing fixture.
Disassembly:
When removing and disassembling
nozzles, separate and label all components of each
nozzle. Never interchange components between
*
nozzles.
1.
Remove each nozzle assembly from engine and
remove fuel inlet and return lines.
2.
Clamp nozzle holder body
in
a vise and remove
nozzle cap nut and nozzle.
3.
Install nozzle cap nut loosely to protect lapped
surface for the holder body.
4.
If necessary to disassemble the nozzle further,
reverse pressure adjusting screw and lift out
spring and spindle assembly.
Do
not attempt to disassemble the
nozzles or adjust nozzle pressure
without the proper test equipment.
A
nozzle pressure
tester is essential to do a satlsfactorylob.
25
Redistribution or publication of this document,
by any means, is strictly prohibited.
To Next Page
Loading...
Need help?
General
