F i g u r e 11C-7. F u e l I n j e c t o r M o u n t i n g
The fuel injector outlet opening,
through
w h i c h t h e e x c e s s f u e l o i l r e t u r n s t o th e
fuel return manifold and than back to the
fuel tank, is directly adjacent to the in-
let opening.
Figure 11C-6. Injector
Changing the position of the helices, by
Identification Chart
rotating the plunger, retards or ad-
vances the closing of the ports and the
relieved and the valve spring closes the
beginning and ending of the injection pe-
needle valve, ending injection.
riod. At the same time, it increases or
decreases the amount of fuel injected into
A pressure relief passage has been pro-
the cylinder.
Figure 11C-4 on page
vided in the spring cage to permit
11C-3 shows the various plunger posi-
bleed-off of fuel leaking past the needle
tions from no-load to full-load. With the
pilot in the tip assembly.
c o n t r o l rack
pulled
out
all
the
way
(no-injection), t h e u p p e r p o r t i s n o t
A check valve, directly below the bush-
closed by the helix until after the lower
ing, prevents leakage from the com-
port is uncovered.
Consequently, with
bustion chamber into the fuel injector in
the rack in this position, all of the fuel
case the valve is accidentally held open
is forced back into the supply chamber
by a small particle of dirt. The injector
and no injection of fuel takes place.
plunger is then returned to its original
With the control rack pushed all the way
position by the injector follower spring.
in (full injection), the upper port is
Figure 11C-5 on page 11C-3 shows the
closed shortly after the lower port has
various phases of injector operation by
been covered, thus producing a maximum
the
injector
travel of
vertical
the
effective stroke and maximum injection.
plunger.
From this no injection position to full in-
jection position (full rack movement), the
On the return upward movement of the
contour of the upper helix advances the
the high pressure cylinder
plunger,
closing of the ports and the beginning of
within the bushing is again filled with
injection.
fuel oil through the ports. The constant
circulation of fresh fuel through the in-
j e c t o r renews t h e f u e l s u p p l y i n t h e
G e n e r a l Instructions for Injector Care
chamber, helps cool the injector and also
e f f e c t i v e l y removes a l l t r a c e s o f a i r
a n d Overhaul
which might otherwise accumulate in the
The fuel injector is one of the most im-
system and interfere with accurate meter-
portant and precisely built parts of the
ing of the fuel.
The injection of the correct
engine.
