Testing of injectors
Testing is carried out in a nozzle testing device. The
opening pressure and tightness are the most important
part of the test. The jet pattern is more difficult to evalu-
ate and does not give a reliable indication of the condi-
tion of the nozzle.
A
WARNING!
Observe care when testing the injec-
tors so that unprotected parts of the body are not
hit by the fuel jet from a nozzle. The jet has such
a powerful impact that it can penetrate into the
skin and cause blood poisoning.
Adjusting the opening pressure, injector
A
T
Fig. 103. Adjuster washers (7), injector
Press the nozzle testing device's lever slowly down with
the manometer connected until the nozzle opens and
releases the fuel. Read off at that precise moment the
opening pressure.
I
f the value read off does not correspond with the pre-
scribed value the setting must be changed. This is done
with adjuster washers (Fig. 103).
Note: The opening pressure increases or diminishes
with approx. 1 MPa (10 kp/cm
2
,
142.2 lbf/int) with a
change in the thickness of the adjuster washer by
0.1
mm (.0039 in).
Fuel system
Checking of injectors
Jet pattern
1.
Pump with the nozzle testing device and check the
j
et pattern. The fuel jet should be conformed and in
li
ne with the centre line of the nozzle.
2.
Check that the fuel jet has a circular cross section.
Tightness
Tightness testing examines potential leakage between
the seat of the nozzle needle and the conical sealing
surface of the nozzle sleeve.
1.
Wipe off the nozzle pin so that it is dry.
2.
Pump up the pressure to approx. 2 MPa (20 kp/
cm
2
,
284.4 lbf/int) under the injector's opening pres-
sure (see Technical data). Hold the pressure con-
stant for 10 seconds and check if any fuel drips
from the nozzle pin. Wet nozzles can be approved.
Fit protective caps on the injector's pipe connections
and over the nozzle heads if the injectors are not to be
fitted immediately.
61
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