5-50. HYDRAULIC SYSTEM COMPONENT TESTING
This task covers:
a. Outrigger Jack Cylinder
Main Hydraulic Pump
Pressure Relief Valve (Pump De-Stroke)
b. Relief Valves
Hydraulic System Purging
Tool Kit, General Mechanics,
Automotive (Appendix B, Section III, Item 1)
a. Outrigger Jack Cylinder Double Pilot Operated Check Valves.
(1) Support the weight of the truck with the outriggers (see para 2-14).
(2) Place the aerial/outrigger switch in the neutral position.
(3) Position the outrigger selector valve for the outrigger to be tested to the up position, if the truck lowers
(except for a momentary jerk), the check valve is defective and must be replaced (see para 4-195).
(4) Select outrigger with the aerial/outrigger switch.
(5) Raise the outrigger to the full up position.
(6) Place the aerial/outrigger switch in the neutral position.
(7) Position the outrigger selector valve lever to the down position, if the outrigger starts to go down the
check valve is defective and must be replaced (see para 4-195).
b. Relief Valves.
Any relief valve that has been over tightened can test as faulty,
always loosen and retorque before testing.
A faulty relief valve will return fluid to the reservoir.
(1) Locate the manifold block the relief valve is mounted to (see hydraulic system schematic, Appendix J).
(2) Locate the pressure line leading to the manifold block and disconnect it.
(3) Install a 0-3000 PSI (0-20, 000 kPa) Pressure gauge to relief valve.
(4) Pressurize the affected system. Pressure should indicate 2000 PSI (13, 780 kPa). If pressure reads
over 2000 PSI (13, 780 kPa), replace valve.
(5) Reconnect pressure line to manifold block.