Variable Flow Pumps
Regulator Valve Adjustment (Cont’d)
The load sense system is a dynamic type, which means a
small flow (0.22 to 1.1 gall/1 to 5 litre per minute) is
circulated through the load sense line.
The flow is available due to a 0.02 in (0.6 mm) orifice in the
flow regulator spool in the pump control housing. This orifice
can be blocked or partially restricted which will give poor
performance, slow operating speed and/or low maximum
stall speed. If completely blocked, margin pressure and
stand-by pressure can be difficult to adjust and the loader
services may operate intermittently even though the
excavator operates correctly.
If any of the above symptoms are experienced carry out the
following:
1 Lower the backhoe bucket and loader shovel to rest
on the ground. Stop the engine and remove the
starter key.
2 Gain access to the regulator valve assembly.
3 Disconnect the load sense line at A. Attach a 0.25
inch (6.35 mm) hose to pump of suitable length to
route to a measuring container.
4 Start the engine and measure the flow which should
be at least 0.22 gall/1 litre per minute at 2200 RPM.
5 If the flow is below 0.22gall/1 litre per minute, remove
spool B and clean/unblock orifice C as required.
6 Fit spool B and check the flow as described at step 3
and 4.
7 If the flow is within limits check the stand-by pressure.
Refer to Flow and Pressure Testing.
22 - 6
Section E
Hydraulics
9803/3280
Section E
22 - 6
Issue 1
Service Procedures
347850
B
A
C
B
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