Gas Filling Pressure Of The Pressure Reservoir; Checking The Switching Points For The Warning Display In The Instrument Cluster; Checking The Switching Points Of The Pressure Pump - Porsche 928 Workshop Manual

39
Differential, transaxle system
928
a
a. Gas filling pressure of the pressure reser-
voir.
Turn the ignition key to position 0 at approx.
100 bar. Briefly open the bleeder valve on the
pressure gauge (use collection bottle) and
close it again immediately. The pressure drop
on the pressure gauge should be approx.
5 bar. Continue this process in intervals. The
pressure reservoir gas filling pressure has
been reached at the instant the pointer of the
pressure gauge abruptly falls to 0 bar.
Refer to Page D39-255 for nominal values.
Important:
Always wear goggles and pro-
b. Checking the switching points for the
warning display in the instrument cluster.
During pressure increase:
Start the engine and observe the warning di-
splay. Immediately turn the ignition key to 0
position at the instant the warning display
(PSD off) goes out. Read off the pressure on
the pressure gauge.
During pressure reduction
Produce a system pressure of approx.
140 bar.
Disconnect the plug at the pressure pump.
Start the engine.
Reduce the pressure - in a similar manner to
the procedure described in Gas filling press-
ure of the pressure resewoil - until the war-
ning display (PSD off) lights up. Read off the
pressure on the pressure gauge. Refer to
Page D39-255 for nominal values.
c. Checking the switching points of the
pressure pump
Cut-out pressure:
Turn the ignition key to po-
sition 2. The electrical plug must be plugged
onto the pressure pump for this.
Read off the pressure on the pressure gauge
immediately
after the pump cuts out automat-
ically.
Cut-in pressure:
Turn ignition key to position
2. Wait until the pump cuts out automatically
if necessary. Carefully reduce the system
pressure at the pressure gauge bleeder valve
(use collection bottle) until the pump cuts in
again. Read off the pressure on the pressure
gauge at this moment. Refer to Page D39-
255 for nominal values.
d. Checking the tightness (pressure loss)
of the lock hydraulics.
Turn the ignition key to position 2. Wait until
the pump cuts out automatically. Carefully lo-
wer the system pressure at the pressure
gauge bleeder valve (use collection bottle)
until the pump cuts in again. After the pump
cuts out automatically, turn the ignition key to
position 0 and disconnect the electrical plug
at the pump. Measure the pressure decrease
over time.
The permissible values are given on Page
D39-255.
Note
Depressurize the lock hydraulics before re-
moving the pressure gauge.
D39 - 254
0
PSD diagnosis/Troubleshooting
Printed In Germany - XXW, 1995