How To Clean The Filter - Graco GMax
3900 Instruction Manual

How to Check the Gun Diffuser Operation
Check the diffuser operation weekly. The gun diffuser/
seat (A) breaks up spray and reduces the risk of fluid
injection when the tip is not installed. Perform the test
below. If it fails, replace the entire Needle Kit, Part No.
218–070, as instructed on page 7. Diffuser/seats are
not sold separately since the gun will leak if an old
needle is used with a new diffuser/seat.
1. Follow Pressure Relief Procedure on page 5.
2. Remove the tip guard and spray tip.
3. Start the sprayer and adjust it to the lowest
pressure.
4. Aim the gun into a grounded metal pail while
holding it firmly to the pail. Trigger the gun. If the
fluid emitted is not diffused into an irregular
stream, replace the entire needle kit immediately.
See Fig. 5.

How to Clean the Filter (

Normal daily system flushing removes most buildup on
the filter (17). For a weekly cleaning:
1. Follow Pressure Relief Procedure on page 5.
2. Remove the screw (14).
3. Push up on the trigger guard (12) and swing it
away from the trigger (5).
4. Unscrew the gun handle from the housing (26).
Remove the filter and clean it in compatible
solvent.
Installation/Operation
See Fig. 6.)
5. Apply lithium-base grease to the threads of the
fluid tube (19) and reassemble the gun.
A
Fig. 5
26
5
12
Fig. 6
14
19