35
Charge pressure
Mechanical testing (pressure gauge)
Special tools:
(999) 6065 Pressure gauge
6666 Nipple
The pressure gauge connection hose should be long
enough to enable gauge read-off from the driver seat.
The measuring socket for the charge pressure is located
on the intercooler.
Drive uphill on full engine load and throttle. Read-off
the charge pressure when engine speed passes 2200
r/min. Repeat this several times and compare the read-
ings with the specified charge pressure.
It is important for proper results that full load is main-
tained long enough for the pressure to stabilize itself.
A clogged air filter or blocked air inlet will result in
pressure drop at the compressor inlet. This lowers
the charge pressure and reduces engine power. Be-
fore checking the charge pressure, check the pres-
sure-drop indicator in the inlet hose from the air
cleaner. If its window is full red, it is time to re-
place the air cleaner filter insert.
After testing fit and tighten up the screw plug for the
measuring socket. Make sure it is properly tightened as
there is always a risk that an insufficiently tightened
plug slackens during driving. If the plug drops off, the
charge pressure will drop and notably lower the power
output, Ther is also risk of dirt getting into the engine,
particularly in connection with much idling and engine
braking.
6065
6591
At too low charge pressure:
Check:
–
for compressor wheel damage
–
that the compressor wheel rotates easily
–
that the axial/radial clearance feels normal
–
that the compressor wheel does not scrape against
the compressor housing when pressed axially
–
that the wastegate opens, see Specifications
–
Fuel filter, fuel feed pressure
–
EDC-sensor, charge pressure
–
Control rod travel, injection pump, see Fuel sys-
tem, testing injection pump.
