Figure 11C-77. Types of Injector
Plungers
dened case and result in chipping at the
Figure 11C-76. Injector Rack-To-Gear
helices and seizure or scoring of the
Timing
plunger.
EFFECT OF PRE-IGNITION ON FUEL
REFINISHING INJECTOR FOLLOWER
INJECTOR. Pre-ignition is due to ig-
FACE. When refinishing the face of an
nition o f f u e l o r l u b r i c a t i n g o i l i n t h e
injector follower, it is extremely impor-
combustion chamber before the normal in-
tant that the distance between the fol-
jection period. The piston compresses
lower face and the plunger slot is not
the burning mixture to excessive temper-
less than 1.645" minimum as shown in
atures and pressures and may eventually
Figure 11C-78 on page 11C-49. If this
cause burning of the injector spray tip
distance is less than specified, the
and lead to failure of the injectors in
height of the injector follower in relation
other cylinders.
to the injector body will be altered and
proper injector timing cannot be
When pre-ignition occurs, remove all of
realized.
the injectors and check for burned spray
tips or enlarged spray tip orifices.
FUEL LINES. Flexible fuel lines are
u s e d to facilitate connection of lines lead-
Before replacing the injectors, check the
ing to and from the fuel tank, and to
engine f o r t h e c a u s e o f p r e - i g n i t i o n t o
minimize the effects of any vibration in
avoid recurrence of the problem. Check
the installation.
for damaged blower housing gasket, de-
fective blower oil seals, high crankcase
Be sure a restricted fitting of the proper
pressure, plugged air box drains, inef-
size is used to connect the fuel return
fective oil control rings or dilution of the
line to the fuel return manifold. Do not
use restricted fittings anywhere else in
the fuel system.
INJECTOR PLUNGERS. The fuel output
and the operating characteristics of an
When installing fuel lines, it is recom-
injector are, to a great extent, deter-
mended that connections be tightened on-
mined by the type of plunger used.
ly sufficiently to prevent leakage of fuel;
Three types of plungers are illustrated
thus flared ends of the fuel lines will not
in Figure 11C-77. The beginning of the
become twisted or fractured because of
injection period is controlled by the up-
excessive tightening. After all fuel lines
per helix angle. The lower helix angle
are installed, run the engine long
retards or advances the end of the in-
enough to determine whether or not all
jection
period.
Therefore,
it
is
connections are sufficiently tight. If
imperative that the correct plunger is in-
any leaks occur, tighten the connections
stalled
whenever
an
injector
is
only enough to stop the leak. Also
overhauled.
check
the
filter
cover
bolts
for
tightness.
If injectors with different type plungers
(and
spray
tips)
are
mixed
in
an
LOCATING AIR LEAKS IN FUEL LINES.
engine, erratic operation will result and
Air drawn into the fuel system may re-
may cause serious damage to the engine
sult in uneven running of the engine,
or to the machine.
stalling when idling, or a loss of power.
Poor engine operation is particularly no-
Injector plungers cannot be reworked to
ticeable at the lower engine speeds. An
change the output or operating charac-
opening in the fuel suction lines may be
teristics. Grinding will destroy the har-
11C-38
