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6. Start engine and adjust pressure compensator
(3) to obtain 3325 psi (22,923 kPa) on the pres-
sure gauge at the "GPA" pump port. Tighten
compensator jam nut.
* Record on Data Sheet
7. Shut down the engine and allow the accumulators
to bleed down.
8. Back out unloader valve adjustment screw (2,
Figure 10-1) completely.
9. Start engine and allow pump pressure to build
until the pump unloads.
NOTE: When the steering pump unloads, pump output
pressure at the "GPA" pressure test port will drop to
approximately 200 to 400 psi (1380 to 2760 kPa).
10. Steer the truck to cause the accumulator pressure
to drop until the pump loads.
11. Observe increasing pressure readings on the
gauge installed at the bleeddown manifold test
port "TP2" (3, Figure 10-2).
When pressure increases to 3000 to 3050
psi (20,680 to 21,025 kPa), adjust unloader
valve by turning adjustment screw clockwise
until the pump unloads and pressure begins
to decrease.
* Record on Data Sheet
12. Steer the truck slowly again while observing "TP2"
steering pressure gauge.
The pump must reload when pressure drops
to 2750 psi (18,960 kPa) minimum.
* Record on Data Sheet
13. If minimum reloading pressure in step 12. is not
correct, repeat unloader valve adjustment, steps
11. and 12.
NOTE: The critical pressure setting is the 2750 psi
(18,960 kPa) when the pump loads. The unloading
pressure follows the loading pressure adjustment and
should occur at approximately 3025 psi (20,855 kPa).
14. Tighten jam nut to lock pressure adjustment.
15. Steer truck to cause system to cycle several times
to verify system pressure begins to increase
(pump cycles from unload to load) once pressure
has dropped to 2750 psi (18,960 kPa).
16. Shut down engine and allow accumulators to
bleed down completely. Turn the steering wheel
to verify no pressure remains.
17. Remove gauges and cap test ports.
L10012
Steering Control Unit and Flow Amplifier
Leakage Test
1. Disconnect the flow amplifier return hose (9,
Figure 10-2) at the bleeddown manifold. Plug the
port on the bleeddown manifold.
2. Disconnect steering control unit return hose at
the flow amplifier. Install a plug in the open flow
amplifier port. Do not turn steering wheel with
hoses disconnected!
3. Start engine and allow steering system to reach
normal operating pressure.
4. Measure leakage from flow amplifier return hose
removed in step 1.:
* Record on Data Sheet
5. Measure leakage from steering control unit return
hose removed in step 2.:
* Record on Data Sheet
6. Shut down engine and allow accumulators to
bleed down completely. Steer the truck to verify
all pressure has bled off.
Bleeddown Manifold Leakage Test
1. With hoses disconnected in "Steering Control
Unit and Flow Amplifier Leakage Test" still dis-
connected, disconnect the hoist pilot valve return
hose (14, Figure 10-2) located on the side of the
bleeddown manifold.
2. Before performing the next step, it will be neces-
sary to draw a vacuum on the hydraulic tank to
prevent oil loss when the bleeddown manifold
tank return line is disconnected.
Hydraulic Check-out Procedure
Maximum permissible leakage is 50 cubic
inches (820 ml) per minute.
If leakage is excessive, the flow amplifier
should be repaired or replaced.
Maximum permissible leakage is 10 cubic
inches (164 ml) per minute.
If leakage is excessive, the steering control
valve should be repaired or replaced.
L10-3
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Table of Contents
Troubleshooting
