Graco Inc. 307-712 Paint Sprayer User Manual


 
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