113
Model Code Page
22. Fuel system
1. 9. 1992
6000--8750 223 5
G. Removing injec tors
1. Clean the injectors and the area around them. Disconnect
the delivery pipes and the leak---off pipes.
9051 71300
3. Remove the injector attaching nuts (13 mm) and remove
the injecto r from the cylinder head. Fit protecti ve plugs to all
connections. If the injector does not rise by hand, use puller
9051 71300.
4. Remove the sealing washers from the bottom of the injector
location in the cylinder head if they do no come out with the
injector
H. Inspecting injectors
N.B. When pressure testing the injectors, it is important to
avoid the nozzle end as the fuel jetting out easily penetrates
the skin. Also bear in mind that the fuel ”mist” is dangerous to
inhale.
1. Clean the injector with cleaning fluid and a soft brush.
The carbon deposits must not be knocked off or removed in
anyotherwaywhichmaydamagethenozzle.
2. Secure the injector in a test bench and check the follow-
ing:
--- injector opening pressure
--- the properties of the chattering (creaking) sound and the
form of the spray pattern
--- sealing of nozzle valve against its seat
Opening pressure
Pump a few times to fill the injector. Increase the pressure in
the injector until the chatter ing (cre aking) sound becomes
audible. Read off the opening pressure of the injector. If the
opening pressure deviates from the given value (230±5 bar),
the injector shoul d be taken apart and checked.
Adjustment is achieved by changing the shims. The thickness
of the shims varies from 1.00---1,90 mm and they are available
in increments of 0,05 mm. A thicker shim will raise the opening
pressure while a thinner one lowers it. A difference in shim
thickness of 0,05 mm changes the opening pressure by ap-
prox. 5,0 bar. As the opening pressure of the injector drops
slightly after adjustment, the opening pressure should be set
toapproximately 10 bar above thevalue given in thespecifica-
tions. This value applies both to new and used injector.
Chattering sound properties
Testing with a hand powered pump does not create the same
circumst ances as when the injectoris fitted inthe engine.Only
with new nozzles are the test results reliable. With used
nozzles, there is no chattering (creaking) sound when the
tester is pumped at a certain rate. This has to do with the de-
sign of the nozzles.
However, with a rapid pumping on the tester handle, it should
be possible to hear the chattering (creaking) sound or/and
see a mist of the fuel jetting out.
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