Graco Inc GX-7 400, 311321H, GX-7A Replace End Cap and Air Piston Assembly, GX-7 DI Shown

Replace End Cap and Air Piston Assembly

	End Cap
	Spacer
Piston Assembly
		Rear
Front U-Cup Seal	Piston	U-Cup
		Seal

Spring

Socket Head Cap Screw

Cylinder Clamp

GX-7 DI Shown

FIG. 25: GX-7 DI End Cap and Air Piston Assembly

1.Clean gun according to Clean Spray Gun Procedure, page 20.

2.Loosen rear packing nut 1-2 turns.

3.Push safety stop partially forward, rotate counterclockwise, and slide safety stop off air cylinder.

4.Remove valving rod. See Remove Center- line Components, page 22.

5.Disconnect air supply from gun.

6.Remove rear head cap screw and cylinder clamp from handle.

7.Remove end cap from air cylinder.

8.Inspect end cap o-ring. Replace if dam- aged. Install new end cap o-ring after lightly coating it with Lubriplate grease.

9.Inspect rear U-cup seal or o-ring for dam- age. Replace if necessary. If removed,

Repair

ensure “cup” faces front of air cylinder when replacing.

10.By hand, pull piston assembly out of air cyl- inder and inspect o-ring for damage. Replace if necessary. Apply Lubriplate grease prior to installation.

11.If air was escaping around piston rod dur- ing operation, replace front u-cup seal or o-ring. Apply Lubriplate grease and ensure “cup” faces rear of air cylinder.

12.Insert piston and rod assembly into air cyl- inder. Take care to not damage front cup seal as rod passes through.

13.Insert piston spring. (For GX-7 DI models, also insert piston spacer.)

14.Reinstall end cap into air cylinder.

15.Retighten rear socket head cap screw and cylinder clamp to handle.

16.Reinstall valving rod. Connect valving rod to draw bar. Lubricate and thread into end cap.

17.Adjust valving rod; see Valving Rod Adjustment, page 16.

18.Slide safety stop onto rear of air cylinder. Push safety stop partially forward and rotate clockwise to set to OPEN.

19.Set safety stop to CLOSED (SERVICE).

20.Tighten rear packing nut.

311321H 25