Theory of Operation
PILOT CONTROLLER OPERATION--NEUTRAL
G BALANCE SPRING
H RETURN SPRING
I TO RESERVOIR
J TO CONTROL VALVE
K FROM PILOT PUMP
L PILOT OIL
M RETURN OIL
I TO HYDRAULIC OIL TANK
P PILOT CONTROLLER - NEUTRAL
for correct operation of controller. The balance and
Two hand-operated pilot controllers (right and left) are
return springs used in ports 1 and 3 are different than
used to control the dig functions. Each controller
the balance and return springs used in ports 2 and 4.
assembly contains four valve assemblies, one for each
The ports numbers are stamped on the housing.
direction of each function.
In neutral (P), the spool is pushed up by the return
The pilot controller consists of the plunger (D), sleeve
spring to block oil from the pilot pump (K) to control
(F), spring guide (C), retainer (N), spool (B), piston (A),
valve (J) pilot cap. With the spool up, the passage to
balance spring (G), shims (O), and return spring (H).
the control valve pilot cap is connected to the hydraulic
The spools are select fitted to the bores in the
oil tank (I).
housing. The quantity of shims for each balance spring
and spool assembly has been determine at the factory