IMPLEMENT AND STEERING HYDRAULIC SYSTEM CONTINUED
Low Pressure Standby
When the engine is running with the control valves in the HOLD position, there is no signal oil pressure in the line
to the chamber. Without signal oil pressure in the chamber, system oil pressure in the chamber moves the margin
spool to the right against the force of springs. Pump oil then flows through two passages to the large actuator
piston. The large actuator piston moves the swashplate toward the minimum angle that is required for enough
output to maintain system pressure at 525 psi (3,600 kPa).
N OT E
Do not confuse low pressure standby with the margin pressure. Margin pressure is 305 psi
(2,100 kPa). The pressure that is required to compress the springs is 305 psi (2,100 kPa).
This pressure is not sufficient to move the swashplate against the force of the actuator
spring and of the small actuator piston. Pump output increases until the swashplate can
move against the small actuator piston and the actuator spring. System pressure then
stays at 525 psi, (3,600 kPa) which is Low Pressure Standby. Margin pressure can only be
measured in a non-stall load sensing condition. Some variation in low pressure standby
can occur from low idle to high idle.
Figure 15. Pump and Compensator Operation (Low Pressure Standby).