95
Checking/adjusting opening pressure
Connect up a pressure gauge. Slowly push down
the nozzle tester lever until the nozzle opens and
releases fuel. Read-off the opening pressure.
Volvo specifies an adjusting pressure in addition to
the opening pressure. The adjusting pressure refers
to new injectors with new thrust springs. It is high-
er than the opening pressure and provides a certain
margin to allow for thrust spring fatigue.
If the opening pressure obtained when testing does
not comply with the specifications, adjust to the
correct opening pressure with the help of adjusting
shims.
Spray pattern
At a high pumping speed of 4–6 pump strokes per sec-
ond, the spray pattern should be uniform and the fuel
atomized.
Leakage check
Check for fuel leaks between the tip of the nozzle nee-
dle and the tapered sealing surface of the nozzle sleeve.
Wipe the nozzle tip dry. Connect up a pressure gauge
and pump the pressure to approx. 200 kPa below the
injector opening pressure. Keep the pressure constant
for 10 seconds. No fuel should drip from the nozzle tip.
Chatter test
Normally only new injectors emit a chatter noise.
The contact area between the nozzle needle and the seat
is narrow as the parts are manufactured with a small
angle difference.
Cleaning copper sleeve before
installing injectors
Special tool:
(981) 2546 Sleeve brush
The copper sleeve seat must be cleaned in order to get
proper sealing between the injector and copper sleeve.
Slide down the installation
sleeve to compress the
brush.
Press down the brush
and clean the copper
sleeve.
Place the installation sleeve
over the copper sleeve.
Shims
for pressure setting
Slide the installation sleeve
over the brush before
fitting the brush in the
machine.
After the injector has been in use for a short time, this
difference diminishes and the contact area increases so
that the chatter noise should eventually die out.
The chatter does not have any effect on the injector
when installed in the engine.
Servicing nozzle tester
If the test fuel has been contaminated by dirt, etc., it
must be renewed. Also the nozzle tester filter insert
must be replaced or removed and cleaned in fuel.
When filling with new test fuel, flush the nozzle tester
by pumping the lever, no injector fitted.
Check the pressure gauge reading at intervals, using a
test gauge. If the pressure gauge shows incorrect read-
ings, it should be replaced. Minor deviations can be
corrected by checking against a correction table.