Troubleshooting - Terex ASV SR70 Service & Repair Manual

Check your readings against that stated below. If your
readings differ, relief replacement and or component
repair may be required.
Pressures should read:
• 5500 PSI when the relief is reached in attempted
forward or reverse motion.
Drive pressure troubleshooting:
8. If one reading is low, swap the relief valve with a
similar one and recheck. If the reading improves,
replace the faulty relief valve.
9. If two readings are low, but on different circuits
(pumps), perform step 8 for both.
10. If both readings are low on one pump, disconnect
the drive hoses from the suspected ports and plug
them at the pump. Cap the hoses to prevent con-
tamination and then recheck the pressures at
those ports. If the reading improves, the drive
motor is at fault. If the reading does not improve,
one pump (in the tandem assembly) is at fault.
11. If all 4 readings are low, it is unlikely that all four
relief valves are faulty. The tandem pumps are
most likely not working properly.
Relief Valves
17-9
Test Ports
(see note)
17-10
Posi-Power Pressure Check
Posi-power is a function of the tandem drive pump
assembly. The posi-power control reads charge flow
(which is directly related to engine rpm) and adjusts
drive pump flow to maximize torque and prevent
engine stall during high load conditions.
This procedure should only be performed if you
suspect that the Posi-Power relief valve is faulty. In
performing this procedure you risk contaminating
your hydraulic system if your equipment and work-
ing environment is not clean.
Make certain all couplers, fittings and hoses used
during this process are clean and free of contami-
nants that may potentially cause damage to the
hydraulic pump and or system components!
17-11
To check Posi-Power pressure:
1. With the engine off and cool, disconnect and cap
the posi-power outlet hose from the port on the top
of the drive pump assembly. (figure 17-11)
2. Remove the fitting from the pump assembly and
install a quick coupler similar to the one installed in
test port A or B in its place.
3. Attach a gauge to the quick coupler and route it so
that you or an assistant can read the gauge during
operation.
4. Make sure all bystanders are clear of moving parts
and start the engine.
5. At low rpm, posi-power pressure should read 180
+/- 40 psi. (475 +/- 40 at high rpm)
17-5
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Rubber Track Loader
17. Hydraulic Pressure & Flow
!WARNING!
Posi-Power
Adjustment
Posi-Power
Outlet