Service manual
Table Of Contents
(a) Initial throttled spray
When the nozzle is producing only this spray,
atomization
is
generally poor and the pattern
is
rather straight than conical, there being more
or less after-dribble,
that
is, fuel dribbling after
injection. All these are due
to
the fact
that
the
fuel being injected
is
being throttled by the
pintle prptruding from the
valve.
While
the nozzle
is
making this spray,
see
if
the
needle
valve
chatters in synchronism with the
cyclic motion
of
the lever;
if
so, then the needle
valve
is
free from any sticking or hitching
tendency and,
if
not,
the nozzle and needle
valve
must be cleaned
by
washing and re-tested.
Off-center spray
or
directionally erratic spray,
if
noted, should be taken
to
mean that the
injection nozzle needs thorough cleaning.
(b) Terminating main spray
With the tester lever operated at a rate
of
4
to
6 cycles per second, the initial throttle spray is
hardly visible. The spray under this condition
may be regarded
as
main spray.
The main spray should
be
a good straight cone,
consisting
of
fmely atomized fuel particles
without any large droplets, and should
termi-
nate with
no
dribble
at
the tip,
not
to
mention
of
any fuel dripping.
(3) Seating tightness
An injection nozzle tested and adjusted
as
above,
and found
to
produce a good spray pattern may
be
re-used in the engine provided
that
it passes
this fmal test - seating tightness test.
With the injection nozzle mounted on the nozzle
tester, raise the pressure slowly
to
100
or
110
kg/cm
2
(1422
or
1564 psi) (without exceeding the
set pressure
of
120 kg/cm
2
(1706 psi), so
that
the
needle
valve
will
not
unseat). Hold the pressure
and observe the nozzle tip: there should
be
no
evidence
of
fuel oozing
out
to form a dribble.
If
such evidence
is
noted, then the contacting faces
of
the needle
valve
and seat must be repaired by
lapping in the manner already suggested or the
injection nozzle
as
a whole must be replaced.
-63
-