Graco Inc. 218-745 - Manual (Page 21)

21 307-712
SERVICE
5. Carefully remove the fluid needle assembly (9) from
the rear part of the gun barrel (20). See Fig 15. If the
packing assembly (9a) or insulator (9g) are still in
the barrel, insert the packing removal rod (66d) into
the front of the barrel to gently push them out. Refer
to Fig 16.
NOTE: If the insulator (9g) is removed, be sure to install
it so the insulator end with holes is facing the
packing assembly (9a).
6. Wipe the internal surfaces of the barrel clean with a
soft brush or cloth.
CAUTION
Clean all parts in nonĆconductive solvent compatĆ
ible with the fluid being used, such as xylol or minĆ
eral spirits. Use of conductive solvents can cause
the gun to malfunction.
7. Remove the packing assembly (9a) from the needle
(9b).
NOTE: If the position of the adjusting nut (9c) is
changed, install the adjusting nut to the apĆ
proximate dimension shown in Fig 15. (Final adĆ
justment will be made in step 15.) If the spring
(9f) was removed, reinstall it over the nut (9d).
8. Install the new packing assembly (9a).
CAUTION
Carefully screw needle (9b) into new packing
assembly (9a) to avoid damaging the seals.
9. Test the drag on the fluid needle. It should be apĆ
proximately 2.5 to 3 lbs (use a small spring scale to
measure). If the adjustment is out of tolerance,
tighten or loosen the adjusting screw on the packĆ
ing assembly (9a) slightly and retest. Continue to
adjust until the tolerance is correct.
10. Install the entire fluid needle assembly (9) into the
gun barrel, from the back of the barrel.
11. Firmly tighten the packing nut (9e) down until it botĆ
toms.
CAUTION
When checking the fluid needle movement, DO
NOT move the needle out of the gun barrel more
than 6.35 mm (1/4 in.) to avoid pulling the needle
out of the packing area and damaging the packĆ
ings.
12. Install the barrel as described under Barrel
Removal.
13. Install the electrode as described under Electrode
Replacement.
14. Install the air cap assembly and fluid nozzle as
described in To Clean or Change Air Cap and
Fluid Nozzle.
15. Trigger the gun to check the needle adjustment.
The air should come fully on before the fluid comes
on. Adjust the needle adjusting nut (9c) until the
proper lead and lag is achieved.
If the fluid comes on too soon, remove the trigger
and back the needle adjusting nut (9c) out (away
from the barrel) slightly.
If the fluid comes on too late, tighten the needle
adjusting nut (9c) slightly (turn towards barrel).
After adjustment is complete, tighten the locking nut
(9d) against the adjusting nut (9c).
Fig 15
20
9
KEY
9 Fluid Needle Assembly
9c Needle Adjusting Nut
20 Gun Barrel
132.7 mm
(5.2 in.)
9
9a
9b
9c
9e
9f
9g
Fig 16
KEY
9 Fluid Needle Assembly
9a Needle Packing Assembly
9b Fluid Needle
9c Adjusting Nut
9d Locking Nut
9e Packing Nut
9f Spring
9g Insulator
9c
9d