Graco GMax 3900 User Manual

Graco GMax 3900

73 pages

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309XXX

Rev. A

First choice when

quality counts.

t

Model 232621

8695A

INSTRUCTIONS

INSTRUCTIONS

KEEP FOR REFERENCE.

Read this and all related manuals for

important warnings and instructions.

GMaxr 3900, 5900, 5900HD, 7900

Airless Paint Sprayers

3300 psi (227 bar, 22.7 MPa ) Maximum Working Pressure

Table of Manuals

Operation 308867. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Displacement Pump 308798. . . . . . . . . . . . . . . . . . . . . .

Spray Gun 307614. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Spray Tip 308644. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

PC Board 308919. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Drain Valve Kit 308961. . . . . . . . . . . . . . . . . . . . . . . . . . .

GRACO INC. P.O. BOX 1441 MINNEAPOLIS, MN 55440–1441

ECOPYRIGHT 1999, GRACO INC.

Graco Inc. is registered to I.S. EN ISO 9001

Questions and Answers:

B
Betty JohnsonAug 6, 2025
What to do if fluid is spitting from the gun of my Graco GMax 3900?
- M
  Mary MoranAug 7, 2025
  If fluid is spitting from the gun of your Graco Paint Sprayer, it may be due to air in the pump or hose. Check and tighten all fluid connections, and then reprime the pump. Also, check if the tip is partially clogged and clear it if necessary. Ensure that your fluid supply is not low or empty; refill it and prime the pump. Make sure you check the fluid supply often to prevent running the pump dry.
R
Rebecca StoutAug 13, 2025
Why is the pump difficult to prime on my Graco Paint Sprayer?
- B
  Brian LambAug 13, 2025
  If the pump of your Graco Paint Sprayer is difficult to prime, first check for air in the pump or hose. Ensure all fluid connections are tight and reduce the engine speed, cycling the pump as slowly as possible during priming. Also, the intake valve may be leaking; clean the intake valve, ensuring the ball seat is in good condition and the ball seats well. If the paint is too thick, thin it according to the supplier’s recommendations. If the engine speed is too high, decrease the throttle setting before priming the pump. Lastly, consider that worn pump packings can also cause priming issues.
S
Sandra PorterAug 25, 2025
How to fix excessive paint leakage into the throat packing nut on my Graco GMax 3900?
- K
  Kimberly MartinezAug 26, 2025
  If you're experiencing excessive paint leakage into the throat packing nut of your Graco Paint Sprayer, the throat packing nut may be loose. Remove the throat packing nut spacer and tighten the throat packing nut just enough to stop the leakage. If the problem persists, the throat packings or displacement rod may be worn or damaged, requiring replacement.

Graco GMax 3900 Specifications

General

Brand	Graco
Model	GMax 3900
Category	Paint Sprayer
Language	English

Summary

GMax® 3900, 5900, 5900HD, 7900 Airless Paint Sprayers

OPERATION

Instructions and procedures for operating the paint sprayer.

INSTRUCTIONS

Read all instructions and warnings before setup or operation.

CONTROLS

On/Off Switch

Control for powering the unit on and off.

Pressure Control

Adjusts the fluid output pressure of the sprayer.

Trigger Lock

Mechanism to secure the spray gun trigger.

PRESSURE RELIEF

STARTUP

Start Engine

Procedure for starting the engine.

Maintenance

Troubleshooting

Component Identification and Function

Service

Pressure Relief Procedure

Steps to safely relieve system pressure before maintenance.

Repair When Pump Is Off The Sprayer

Procedure for repairing the pump when detached from the sprayer.

Assembling the pump

Instructions for reassembling the pump after servicing.

Repair When Pump Is On The Sprayer

Procedure for repairing the pump while it is on the sprayer.

Cross Sectional Reference

Diagram showing internal pump components and their relationships.

Technical Data

Graco Standard Warranty

ADDITIONAL WARRANTY COVERAGE

Details on extended warranty and wear warranty programs.

Installation/Operation

System Requirements

Essential components and conditions for proper operation.

Grounding

Procedures to ensure proper electrical grounding for safety.

How to Use the Gun Trigger Safety

Instructions for engaging and disengaging the trigger safety.

How to Use the Gun

Steps for connecting the hose and priming the system.

How to Adjust the Spray Pattern

Techniques for adjusting spray pattern direction and coverage.

How to Clean the Spray Tip and Clear a Spray Tip Obstruction

Methods for cleaning tips and clearing clogs.

How to Clean the Filter

Instructions for cleaning the system's fluid filter.

How to Flush the Gun

Steps for flushing the pump and gun with water or solvent.

Parts List

Accessories

RAC TIP GUARD ASSEMBLY

INSTALLATION

Instructions for installing the RAC tip guard assembly.

AVAILABLE TIPS

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