JLG sky trak mmv Service Manual page 409

g. Main Control Valve Assembly
This section covers assembly of the outlet (1), extend/
retract (2), lift/lower (3) and mid-inlet (4) sections.
Note: ALWAYS replace o-rings with new o-rings
lubricated with clean hydraulic oil to help ensure a leak-
proof seal and proper vehicle performance.
Assemble the Outlet Section
1. Install the shut-off plug (5) and new oiled o-ring (6)
into the outlet section (1).
2. Install new oiled o-ring (7), plug (8), new oiled o-ring
(9), plug (10), new oiled o-ring (11), plug (12), new
oiled o-ring (13) and plug (14) into the outlet section
(1).
3. Install the main relief valve (15) after assembling it
using the procedure that follows.
Assemble the Main Relief Valve (Outlet Section)
Note: There is a seal and spring kit for assembling the
relief valve.
1. Install the plug (16) into the body (17).
2. Install the poppet (18), spring retainer (19), new
spring (20), shim (21) and new oiled o-ring (22) into
the body (17). Install the nut (23).
3. Install the adjustment screw (24) and new oiled o-
ring (25). Install the nut (26).
4. Install a new seal (27) and the relief valve (15) onto
the outlet section (1).
Assemble the Mid-Inlet Section
1. Install the shut-off plug (28) and new oiled
o-ring (29) into the mid-inlet section (4).
2. Install the plug (30) and new oiled o-ring (31) into the
mid-inlet section (4).
3. Install the shuttle (32) into the mid-inlet section (4).
Model MMV Rev. 12/04
Assemble the Lift/Lower Section
1. Install the anti-void assembly (33) with a new oiled
o-ring (34) into the lift/lower section (3).
2. Assemble the end mechanism (40) by inserting a
new oiled o-ring (41) in the spool cap retainer (42).
Install the flat washer (43), spacer (44), spring (45),
another flat washer (46) and spool end (47) into the
spool cap (48). Install the spool cap retainer (42)
onto the spool cap (48). Place the retainer (49) on
the other end.
3. Insert a new oiled o-ring (50) into the section and
attach this end mechanism (40) with the
capscrews (51).
4. Assemble the other end mechanism (35) by
inserting the spool cap (36) into the retainer (37).
5. Insert a new oiled o-ring (38) onto the section and
attach the end mechanism (35) with the
capscrews (39).
6. Install the relief valve (52), after assembling it, using
the procedures that follow.
7. Insert the shuttle (53), poppet (54) and spring (55)
into the section.
8. Place a new oiled o-ring (56) between the lift/lower
section (3) and the mid-inlet section (4) and slide the
lift/lower section onto the tie rods.
Assemble Relief Valve (Lift/Lower Sections)
On the lift/lower section (3), the relief valve is on the "A"
side (57) and is preset at 3000 ±50 psi (207 ±3,5 bar).
Note: There is a seal and spring kit for assembling the
relief valve.
1. Install the poppet (58) and new spring (59) into the
plug (60). Install the adjustment screw (61) and new
oiled o-ring (62) with the nut (63) onto the plug (60).
2. Install the larger poppet (64), smaller poppet (65),
new back-up ring (66), new oiled o-ring (67), poppet
(68) and new small spring (69) into the body (70).
Install the new oiled o-ring (71), new back-up ring
(72) and new large spring (73) into the body (70).
3. Install the new oiled o-ring (74) and plug (60) onto
the body (70).
4. Using a wrench on the body (70), install the relief
valve (52) and new oiled o-ring (75) into the lift/lower
section (3) assembly
Hydraulic System
9.111