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2
Checking and repairing fuel injectors
33
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,
see page 34.
Fig. 2
Check injector assembly.
Connect the nozzle’s supply connection to the test
unit’s pressure line.
Danger:
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 Æ.
The initial tension of the compression spring Å de-
creases if a high number of operating hours has
been clocked up.
Consequently, the injection pressure drops slightly.
When repairing injection nozzles, always set the
opening pressure to the upper limit (+ 8 bar).
Note:
Shims are available in 0.05 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.
8
7
6
5
4
3
2
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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