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Checking and repairing fuel injectors
32
Checking fuel injectors
Fig. 1
The nozzle tester (manual test stand) is used to
check the
– opening pressure
– tightness
– spray pattern of the injection nozzle.
Use pure testing oil or pure Diesel fuel for the test.
Prior to testing, clean nozzle and check it for wear.
Fig. 2
Check injector assembly.
Connect the nozzle’s supply connection to the test
unit’s pressure line.
Caution:
The high opening pressure may lead
to severe injuries. Do not place hands
under the jet. Wear safety goggles.
1. Checking opening pressure:
Switch on the pressure gauge and slowly press
lever downwards until the nozzle emits a jet with a
light grating noise.
Read opening pressure from the pressure gauge.
In the event of a pressure deviation insert a differ-
ent shim. If the pressure is too low, insert thicker
shims, if it is too high, insert thinner shims (7). The
initial tension of the compression spring (6) de-
creases if a high number of operating hours has
been clocked up. Consequently, the injection pres-
sure drops slightly. When repairing injection
nozzles, always set the opening pressure to the
upper limit (+ 8 bar).
Note:
Shims are available in 0.02 mm steps from
1.0 mm to 1.98 mm.
2. Checking tightness:
Actuate hand lever. At a pressure of 20 bar below
the opening pressure set not a single drop must
fall from the nozzle opening within 10 sec.
3. Checking jet:
Switch off pressure gauge and carry out some
swift strokes. The nozzle must emit an audible
grating noise and/or a well-atomised jet.
Nozzles that satisfy these three requirements can
be reused.
2581
2
3
4
5
6
7
8
2644
1
1 Seal
2 Nozzle tension nut
3 Injection nozzle
4 Intermediate washer
5 Pressure pin
6 Compression spring
7 Shim
8 Circlip
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