Fuel injection nozzles
Checking fuel injection nozzles
The checks on injection nozzle operating conditions include injec-
tion nozzle spraying efficiency and calibration.
However, it is recommended that the utmost cleanliness rules be
strictly observed and a thorough test on the hydraulic seal of the
different system fittings be performed. As a matter of fact even a
small leakage would invalid the tests carried out.
Injection nozzle calibration
Check pressure reading at which the nozzle needle begins to be
lifted from its seat thus determining the injection starting.
This pressure should be within the recommended specifications.
For this reason, each time that calibrating pressure readings differ
from specifications the injection nozzle should be adjusted as
required.
To perform the above checks, the use of a pump connected to the
injection nozzle to be tested by a piping is unavoidable.
(Prior to performing the test the fuel recovery plug should be
removed).
The following procedure shall apply:
Operate the pump lever (fig. 4) a few times to force any air out of
system.
Slowly operate the pump lever and notice the pressure reading
right in the moment the injection begins. This pressure should be
180 bar. If readings differing from that specified are indicated, it
will be necessary to adjust the pressure spring by simply adding
or removing the special spring preloading shims.
To gain access to spring adjustment, remove first the lower cap
of the injection nozzle holder and then add or remove shims
bewteen spring and flat cap until the desired nozzle calibrating
pressure is obtained.
Fig. 1 - Injection nozzle assembly.
Fig. 2 - Injection nozzle section.
Fig. 3 - Spring load adjustment.
engine
fuel system
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