Piston Repair - Graco PRO AA5500SC Instructions And Parts List

Piston Repair

1. Remove the retaining nut (1), tip guard, (12), air
cap (15), spray tip (13), and gun shroud (2) as
instructed on page 31.
2. Remove the jam nut (8), actuator arm (19), and
adjustment nut (17). See Fig. 41 .
3. Push on the piston rod (23g) to push the piston
assembly out the back of the gun.
4. Inspect the o-rings (23a, 23b, 23c) and u-cup
packing (23f) for damage. See Fig. 42 . Refer to
Fig. 43 to isolate any air leakage problems.
5. Lubricate the o-rings (23a, 23b, 23c) and u-cup
packing (23f) with petroleum jelly.
6. Align the stems (23d) with the holes in the gun
body and press the piston assembly into the back
of the gun until it bottoms.
7. Install the actuator arm (19) and jam nut (8), with
the jam nut assembled flush to the end of the pis-
ton rod. Adjust the nut (17) as instructed on page
35. Tighten the jam nut (8) securely to prevent it
from loosening during operation.
8. If done servicing the gun, install the spray tip (13),
air cap (15), tip guard (12), and retaining nut (1) as
instructed on page 31. Tighten the retaining nut
firmly.
9. Test gun resistance as instructed on page 26.
10. Install the gun onto the manifold and bracket as
instructed on page 39.
8 19 17 23g
Fig. 41
Service
23b
Apply a very light coat of lubricant
Align stems (23d) with holes in gun body and press piston
assy. to bottom
Fig. 42
Description Function
O-Ring (23a)
Shaft Air Seal
O-Ring (23a)
Back Air Seal
O-Ring (23b)
Front Air Seal
U-cup (23f)
Cylinder Air
Seal
23b
ATOMIZATION AIR SIDE
Fig. 43
23d
23c
23f
23g
23a
Seals cylinder air along the piston rod
(23g). If air leaks along the piston rod,
replace this o-ring.
Separates the cylinder air pressure from
the atomization air pressure.
Air shut-off seal. If air leaks from the air cap
when the gun is detriggered, replace these
o-rings.
If air leaks from the small vent hole in the
back of the manifold when the gun is trig-
gered, replace the u-cup.
23c
23a
23e
23f