Graco GMAX ll 5900 Convertible Operating instructions

Graco Inc. P.O. Box 1441 Minneapolis, MN 55440-1441
Copyright 2005, Graco Inc. is registered to I.S. EN ISO 9001
310893 rev. J
Repair
GMax™II
3900, 5900, 5900HD, 7900
Airless Sprayers
Korean patent: 10-0647761
- For Portable Airless Spraying of Architectural Coatings and Paints -
3300 psi (22.8 MPa, 228 bar) Maximum Working Pressure
Important Safety Instructions
Read all warnings and instructions in
this manual. Save these instructions.
GMax ll 3900
248683 ✓
248684 ✓
248685 ✓✓
248686 ✓✓
249335 ✓✓
GMax ll 5900
248687 ✓
248688 ✓
248689 ✓✓
248690 ✓✓
249336 ✓✓
GMax ll 5900HD
248698 ✓
248699 ✓✓
GMax ll 7900
248700 ✓
248701 ✓
248702 ✓✓
248703 ✓✓
249337 ✓✓
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Related Manuals
310892 309639
310894 309640

Manual Conventions
2310893J
Contents
WARNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Bearing Housing & Connecting Rod . . . . . . . . . . . 8
Drive Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Pinion Assembly/Clutch Armature/Clamp . . . . . . 10
Clutch Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Pump ON/OFF Switch . . . . . . . . . . . . . . . . . . . . . . 13
Pressure Control . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Displacement Pump . . . . . . . . . . . . . . . . . . . . . . . 16
Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
GMax II 3900 Parts Drawing . . . . . . . . . . . . . . . . . . 20
GMax II 5900/5900HD Parts Drawing. . . . . . . . . . . 22
GMax II 7900 Parts Drawing . . . . . . . . . . . . . . . . . . 24
Parts Drawing and List - Pinion Housing . . . . . . . 26
Lo-Boy Suction Set. . . . . . . . . . . . . . . . . . . . . . . . . 27
Pressure Control and Filter Parts Drawing. . . . . . 28
Parts - Sprayers, RAC X
®
Tip, Gun & Hose . . . . . . . . . . 30
Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Graco Standard Warranty . . . . . . . . . . . . . . . . . . . 32
Manual Conventions
Note
WARNING
WARNING: a potentially hazardous situation which, if
not avoided, could result in death or serious injury.
Warnings in the instructions usually include a symbol
indicating the hazard. Read the general Warnings
section for additional safety information.
Hazard Symbol
CAUTION
CAUTION: a potentially hazardous situation which, if
not avoided, may result in property damage or
destruction of equipment.
Additional helpful information.

Warning
310893J 3
Warning
The following are general warnings related to the setup, use, maintenance and repair of this equipment. Additional,
more specific, warnings may be found throughout the text of this manual, where applicable.
WARNING
FIRE AND EXPLOSION HAZARD
Flammable fumes, such as solvent and paint fumes, in work area can ignite or explode. To help prevent
fire and explosion:
• Use equipment only in well ventilated area.
• Do not fill fuel tank while engine is running or hot; shut off engine and let it cool. Fuel is flammable
and can ignite or explode if spilled on hot surface.
• When flammable liquid is sprayed or used for flushing or cleaning, keep sprayer at least 20 feet (6 m)
away from explosive vapors.
• Eliminate all ignition sources; such as pilot lights, cigarettes, portable electric lamps, and plastic drop
cloths (potential static arc).
• Keep work area free of debris, including solvent, rags and gasoline.
• Do not plug or unplug power cords, or turn power or light switches on or off when flammable fumes
are present.
• Ground equipment and conductive objects in work area. See Grounding instructions.
• Use only grounded hoses.
• Hold gun firmly to side of grounded pail when triggering into pail.
• If there is static sparking or you feel a shock, stop operation immediately. Do not use equipment
until you identify and correct the problem.
SKIN INJECTION HAZARD
High-pressure fluid from gun, hose leaks, or ruptured components will pierce skin. This may look like just
a cut, but it is a serious injury that can result in amputation. Get immediate surgical treatment.
• Do not point gun at anyone or at any part of the body.
• Do not put your hand over the spray tip.
• Do not stop or deflect leaks with your hand, body, glove, or rag.
• Do not spray without tip guard and trigger guard installed.
• Engage trigger lock when not spraying.
• Follow Pressure Relief Procedure in this manual, when you stop spraying and before cleaning,
checking, or servicing equipment.
PRESSURIZED EQUIPMENT HAZARD
Fluid from the gun/dispense valve, leaks, or ruptured components can splash in the eyes or on skin and
cause serious injury.
• Follow Pressure Relief Procedure in this manual, when you stop spraying and before cleaning,
checking, or servicing equipment.
• Tighten all fluid connections before operating the equipment.
• Check hoses, tubes, and couplings daily. Replace worn or damaged parts immediately.
MOVING PARTS HAZARD
Moving parts can pinch or amputate fingers and other body parts.
• Keep clear of moving parts.
• Do not operate equipment with protective guards or covers removed.
• Pressurized equipment can start without warning. Before checking, moving, or servicing equipment,
follow the Pressure Relief Procedure in this manual. Disconnect power or air supply.

Warning
4310893J
EQUIPMENT MISUSE HAZARD
Misuse can cause death or serious injury.
• Do not exceed the maximum working pressure or temperature rating of the lowest rated system
component. See Technical Data in all equipment manuals.
• Use fluids and solvents that are compatible with equipment wetted parts. See Technical Data in all
equipment manuals. Read fluid and solvent manufacturer’s warnings.
• Check equipment daily. Repair or replace worn or damaged parts immediately.
• Do not alter or modify equipment.
• Do not install a shut-off device between filter outlet and gun.
• Use equipment only for its intended purpose. Call your Graco distributor for information.
• Route hoses and cables away from traffic areas, sharp edges, moving parts, and hot surfaces.
• Do not use hoses to pull equipment.
• Keep children and animals away from work area.
• Comply with all applicable safety regulations.
PRESSURIZED ALUMINUM PARTS HAZARD
Do not use 1,1,1-trichloroethane, methylene chloride, other halogenated hydrocarbon solvents or fluids
containing such solvents in pressurized aluminum equipment. Such use can cause serious chemical
reaction and equipment rupture, and result in death, serious injury, and property damage.
SUCTION HAZARD
Never place hands near the pump fluid inlet when pump is operating or pressurized. Powerful suction
could cause serious injury.
CARBON MONOXIDE HAZARD
Exhaust contains poisonous carbon monoxide, which is colorless and odorless. Breathing carbon mon-
oxide can cause death. Do not operate in an enclosed area.
TOXIC FLUID OR FUMES HAZARD
Toxic fluids or fumes can cause serious injury or death if splashed in the eyes or on skin, inhaled, or
swallowed.
• Read MSDS’s to know the specific hazards of the fluids you are using.
• Store hazardous fluid in approved containers, and dispose of it according to applicable guidelines.
BURN HAZARD
Equipment surfaces and fluid that’s heated can become very hot during operation. To avoid severe
burns, do not touch hot fluid or equipment. Wait until equipment/fluid has cooled completely.
PERSONAL PROTECTIVE EQUIPMENT
You must wear appropriate protective equipment when operating, servicing, or when in the operating
area of the equipment to help protect you from serious injury, including eye injury, inhalation of toxic
fumes, burns, and hearing loss. This equipment includes but is not limited to:
• Protective eyewear
• Clothing and respirator as recommended by the fluid and solvent manufacturer
•Gloves
• Hearing protection
RECOIL HAZARD
Brace yourself; gun may recoil when triggered and cause you to fall, which could cause serious injury.
WARNING

Maintenance
310893J 5
Maintenance
Pressure Relief Procedure
1. Lock gun trigger safety.
2. Turn engine ON/OFF switch to OFF.
3. Move pump switch to OFF and turn pressure control knob
fully counterclockwise.
4. Unlock trigger safety. Hold metal part of gun firmly to side
of grounded metal pail, and trigger gun to relieve
pressure.
5. Lock gun trigger safety.
6. Open pressure drain valve. Leave valve open until ready
to spray again.
If you suspect that the spray tip or hose is completely
clogged, or that pressure has not been fully relieved
after following the steps above, VERY SLOWLY loosen
tip guard retaining nut or hose end coupling to relieve
pressure gradually, then loosen completely. Now clear
tip or hose.
DAILY: Check engine oil level and fill as necessary.
DAILY: Check hose for wear and damage.
DAILY: Check that all hose fittings are secure.
DAILY: Check gun safety for proper operation.
DAILY: Check pressure drain valve for proper operation.
DAILY: Check and fill the gas tank.
DAILY: Check level of TSL in displacement pump pack-
ing nut. Fill nut, if necessary. Keep TSL in nut to help
prevent fluid buildup on piston rod and premature wear
of packings and pump corrosion.
AFTER THE FIRST 20 HOURS OF OPERATION:
Drain engine oil and refill with clean oil. Reference
Honda Engines Owner's Manual for correct oil viscosity.
WEEKLY: Remove engine air filter cover and clean ele-
ment. Replace element, if necessary. If operating in an
unusually dusty environment: check filter daily and
replace, if necessary.
Replacement elements can be purchased from your
local HONDA dealer.
AFTER EACH 100 HOURS OF OPERATION:
Change engine oil. Reference Honda Engines Owner's
Manual for correct oil viscosity.
SPARK PLUG: Use only BPR6ES (NGK) or W20EPR-U
(NIPPONDENSO) plug. Gap plug to 0.028 to 0.031 in.
(0.7 to 0.8 mm). Use spark plug wrench when installing
and removing plug.
Premium Sprayers Engine Oil Funnel:
Use the supplied engine oil funnel when draining oil.
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4
CAUTION
For detailed engine maintenance and specifications,
refer to separate Honda Engines Owner's Manual,
supplied.
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Troubleshooting
6310893J
Troubleshooting
Problem Cause Solution
E=XX is displayed Fault condition exists Determine fault correction from table, page 15
Engine will not start Engine switch is OFF Turn engine switch ON
Engine is out of gasoline Refill gas tank. Honda Engines Owner's Man-
ual.
Engine oil level is low Try to start engine. Replenish oil, if necessary.
Honda Engines Owner's Manual.
Spark plug is disconnected or damaged Connect spark plug cable or replace spark plug
Cold engine Use choke
Fuel shutoff lever is OFF Move lever to ON position
Oil is seeping into combustion chamber Remove spark plug. Pull starter 3 to 4 times.
Clean or replace spark plug. Start engine.
Keep sprayer upright to avoid oil seepage
False tripping of WatchDog system.
EMPTY is displayed. Pump does not
run.
Operating conditions out of WatchDog
parameters
Pump output is low, page 7.
Turn pressure down. Contact Graco Technical
Assistance to adjust WatchDog parameters.
Operate without WatchDog active; Manual
310892.
Engine operates, but displacement
pump does not operate
Error code displayed Reference Pressure Control repair, page 15
Pump switch is OFF Turn pump switch ON
Pressure setting too low Turn pressure adjusting knob clockwise to
increase pressure.
Fluid filter (56) is dirty Clean filter. Page 28.
Tip or tip filter is clogged
Clean tip or tip filter. Manual 309639.
Displacement pump piston rod is stuck
due to dried paint
Repair pump. Manual 310894.
Connecting rod is worn or damaged Replace connecting rod. Page 8.
Drive housing is worn or damaged Replace drive housing. Page 9.
Electrical power is not energizing clutch
field
Check wiring connections. Page 12.
Reference
Digital Display Messages . Page 15 .
Reference wiring diagram. Page 29.
With pump switch ON and pressure turned to MAXI-
MUM, use a test light to check for power between clutch
test points on control board.
Remove clutch wires from control board and
measure resistance across clutch coil. At 70° F,
the resistance must be between 1.2 +0.2Ω; if
not, replace pinion housing.
Have pressure control checked by authorized
Graco dealer
Clutch is worn, damaged, or incorrectly
positioned
Adjust or replace clutch. Page 10.
Pinion assembly is worn or damaged Repair or replace pinion assembly. Page10.

Troubleshooting
310893J 7
Problem Cause Solution
Pump output is low Strainer (82) is clogged Clean strainer.
Piston ball is not seating Service piston ball. Manual 310894.
Piston packings are worn or damaged Replace packings. Manual 310894.
O-ring in pump is worn or damaged Replace o-ring. Manual 310894.
Intake valve ball is not seating properly Clean intake valve. Manual 310894.
Intake valve ball is packed with material Clean intake valve. Manual 310894.
Engine speed is too low
Increase throttle setting. Manual 310892.
Clutch is worn or damaged Adjust or replace clutch. Page 10.
Pressure setting is too low Increase pressure. Manual 310892.
Fluid filter (56), tip filter or tip is clogged or
dirty
Clean filter. Manual 310892 or 309639.
Large pressure drop in hose with heavy
materials
Use larger diameter hose and/or reduce
overall length of hose. Use of more than
100 ft of 1/4 in. hose significantly reduces
performance of sprayer. Use 3/8 in. hose
for optimum performance (50 ft minimum).
Excessive paint leakage into throat
packing nut
Throat packing nut is loose Remove throat packing nut spacer. Tighten
throat packing nut just enough to stop leak-
age.
Throat packings are worn or damaged Replace packings. Manual 310894.
Displacement rod is worn or damaged Replace rod. Manual 310894.
Fluid is spitting from gun Air in pump or hose
Check and tighten all fluid connections. Rep-
rime pump. Manual 310892.
Tip is partially clogged Clear tip. Manual 309639.
Fluid supply is low or empty Refill fluid supply. Prime pump. Manual
310892. Check fluid supply often to prevent
running pump dry.
Pump is difficult to prime Air in pump or hose
Check and tighten all fluid connections.
Reduce engine speed and cycle pump as
slowly as possible during priming.
Intake valve is leaking Clean intake valve. Be sure ball seat is not
nicked or worn and that ball seats well.
Reassemble valve.
Pump packings are worn Replace pump packings. Manual 310894.
Paint is too thick Thin the paint according to the supplier's
recommendations
Engine speed is too high Decrease throttle setting before priming
pump. Manual 310892.
Clutch squeaks each time clutch
engages
Clutch surfaces are not matched to each other
when new and may cause noise
Clutch surfaces need to wear into each
other. Noise will dissipate after a day of run
time.
High engine speed at no load Misadjusted throttle setting Reset throttle to 3300 engine rpm at no
load.
Worn engine governor Replace or service engine governor
Gallon counter not working Bad sensor, broken or disconnected wire.
Displaced or missing magnet.
Check connections. Replace sensor or
wire. Reposition or replace magnet.
No display, sprayer operates Display damaged or has bad connection Check connections. Replace display.

Bearing Housing and Connecting Rod
8310893J
Bearing Housing and Connecting Rod
NOTE: The item numbers referenced are for the 5900
Hi-Boy models. The 3900, 7900 and all Lo-Boy models
may have different item numbers. Use the 5900 Hi-Boy
item number and part to find the corresponding alter-
nate part and item number.
Removal
1. Relieve pressure; page 5.
2. FIG. 1. Remove four screws (45) and front cover (44)
3. Remove pump. Refer to Displacement Pump, Removal,
page 16.
4. Remove four screws (41) and washers (42) from bearing
housing (40).
5. Pull connecting rod (43) and lightly tap lower rear of
bearing housing with plastic mallet to loosen from drive
housing (33). Pull bearing housing and connecting rod
assembly off drive housing.
6. Inspect crank (B) and connecting rod (43) for excessive
wear and replace parts as needed.
Installation
1. Evenly lubricate inside of bronze bearing (C) in bearing
housing (40) with high-quality motor oil. Liberally pack top
roller bearing (E), lower bearing (D) inside connecting rod
(43) with bearing grease.
2. Assemble connecting rod (43) to bearing housing (40).
Rotate connecting rod to lowest position.
3. Clean mating surfaces of bearing and drive housings.
4. Align connecting rod with crank (B) and carefully align
locating pins (F) in drive housing (33) with holes in
bearing housing (40). Push bearing housing onto drive
housing or tap into place with plastic mallet.
5. Install screws (41) and washers (42) in bearing housing.
Torque evenly to note 3 value in Fig. 1.
6. Install pump. Refer to Displacement Pump, Installation,
page 14.
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4
CAUTION
DO NOT use bearing housing screws (41) to align or
seat bearing housing with drive housing. Align these
parts with locating pins, to avoid premature bearing
wear.
FIG. 1
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Pack with bearing grease 114819
GMax II 3900: Torque to 200 in-lb (22.6 N.m)
GMax II 5900: Torque to 25 ft-lb (34 N.m)
GMax II 7900: Torque to 40 ft-lb (54 N.m)

Drive Housing
310893J 9
Drive Housing
Removal
1. Relieve pressure; page 5.
2. Remove bearing housing. Refer to Bearing Housing and
Connecting Rod, Removal, page 8.
3. Premium sprayers: Remove two screws (108) and gallon
counter sensor (39).
4. Remove six screws (38).
5. Lightly tap around drive housing (33) to loosen drive
housing. Pull drive housing straight off pinion housing. Be
prepared to support combination gear (32) which may
also come out.
Installation
1. FIG. 2 . Apply all grease supplied with replacement gear
cluster to gear teeth and to areas called out by note 3.
2. FIG. 3. Ensure thrust washers (30, 31; 5900/7900) (30, 31,
72; 3900) are on combination gear (32) and washers (Fig.
2; 33a, 33b) are on crankshaft of drive housing (33) as
shown.
3. Clean mating surfaces of pinion and drive housings.
4. Align gears and push new drive housing straight onto
pinion housing (29) and locating pins (B).
5. Install six screws (38).
6. Install gallon counter sensor (39) with two screws (108).
7. Install bearing housing. Refer to Bearing Housing and
Connecting Rod, Installation, page 8.
8. Install screws (38) in drive housing. Torque evenly to note
3 value in FIG. 2.
9. Install pump. Refer to Displacement Pump, Installation,
page14.
FIG. 3
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4
CAUTION
Premium models: Gallon counter sensor is connected to con-
trol board in pressure control. Pulling on the sensor wires could
cause damage.
CAUTION
Thrust washers may stick to grease inside of drive housing.
Do not lose or misplace.
CAUTION
DO NOT use drive housing screws (38) to align or seat
drive housing with pinion housing. Align these parts with
locating pins, to avoid premature bearing wear.
FIG. 2
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Gallon counter sensor
Pack with grease 114819
GMax II 3900: Torque to 140 ±10 in-lb (15.8 ±1.1N.m)
GMax II 5900: Torque to 200 ±10 in-lb (22.6 ±1.1 N.m)
GMax II 7900: Torque to 200 ±10 in-lb (22.6 ±1.1 N.m)
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Steel

Pinion Assembly/Clutch Armature/Clamp
10 310893J
Pinion Assembly/Clutch Armature/Clamp
Pinion Assembly/Clutch Armature Removal
Pinion Assembly
If pinion assembly (29) is not removed from clutch housing
(19), do 1. through 3. Otherwise, start at 4.
1. Remove drive housing; page 9.
2. FIG. 4. Disconnect clutch cable connectors from inside of
pressure control.
a. FIG. 14 . Remove two screws (71) and swing down
cover (130a).
b. Disconnect engine leads from board to engine.
c. Remove strain reliefs 130r and 123.
3. FIG. 4 . Remove four screws (36) and pinion assembly (29).
FIG. 4
4. FIG. 5. Place pinion assembly (29) on bench with rotor
side up.
5. Remove four screws (28) and lock washers (24). Install
two screws in threaded holes (E) in rotor. Alternately
tighten screws until rotor comes off.
FIG. 5
6. FIG. 6. Remove retaining ring (29b).
7. Turn pinion assembly over and tap pinion shaft (29a) out
with plastic mallet.
FIG. 6
Clutch Armature
8. FIG. 7. Use an impact wrench or wedge something
between clutch armature (25) and clutch housing to hold
engine shaft during removal.
9. Remove four screws (23) and lock washers (24).
10. Remove armature.
FIG. 7
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4
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Pinion Assembly/Clutch Armature/Clamp
310893J 11
Installation
Clutch Armature
1. FIG. 8. Lay two stacks of two dimes on smooth bench
surface.
2. Lay armature (25) on two stacks of dimes.
3. Press center of hub (26) down to bench surface.
FIG. 8
4. Install armature (25) on engine drive shaft.
5. Install four screws (23) and lock washers (24) with torque
of 125 in-lb.
Pinion Assembly
6. FIG. 6. Check o-ring (29d) and replace if missing or
damaged.
7. Tap pinion shaft (29a) in with plastic mallet.
8. Install retaining ring (29b) with beveled side facing up.
9. FIG. 5. Place pinion assembly on bench with rotor side up.
10. Apply Loctite®to screws. Install four screws (28) and lock
washers (24). Alternately torque screws to 125 in-lb until
rotor is secure. Use threaded holes to hold rotor.
11. FIG. 4. Install pinion assembly (29) with four screws (36)
and washers (37).
12. FIG. 14. Connect clutch cable connectors to inside of
pressure control.
Clamp Removal
1. Do Engine Removal.
2. Drain gasoline from tank according to Honda manual.
3. FIG. 9 . Tip engine on side so gas tank is down and air
cleaner is up.
4. FIG. 10. Loosen two screws (24) on clamp (22),
5. Push screwdriver into slot in clamp (22) and remove
clamp.
FIG. 9
Clamp Installation
1. FIG. 10. Install engine shaft key (18)
2. Tap clamp (22) onto engine shaft (A). Maintain dimension
shown note 2. Chamfer must face engine.
3. Check dimension: Place rigid, straight steel bar (B) across
face of clutch housing (19). Use accurate measuring
device to measure distance between bar and face of
clamp. Adjust clamp as necessary. Torque two screws
(24) to 125 ±10 in-lb (14 ±1.1 N·m)
Face of clutch housing
1.550 ± .010 in. (39.37 ± .25 mm) - GMax 3900
2.612 ± .010 in. (66.34 ± .25 mm) - GMax 5900 & 7900
Torque to 125 ±.10 in-lb (14 ±1.1 N·m)
Chamfer this side
FIG. 10
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WARNING
Gasoline can spill and cause a fire or explosion if
engine is tipped on side.
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Clutch Housing
12 310893J
Clutch Housing
Removal
1. FIG. 11. Remove four screws (20) and lock washers (21)
which hold clutch housing (19) to engine.
2. Remove screw (35) from under mounting plate (D).
3. Pull off clutch housing (19).
Installation
1. FIG. 11. Push on clutch housing (19).
2. Install four capscrews (20) and lock washers (21) and
secure clutch housing (19) to engine. Torque to 200 in-lb
(22.6 N·m).
3. Install screw (35) from beneath mounting plate (D).
Torque to 26 ft-lb (35.2 N·m).
FIG. 11
Engine
Removal
NOTE: All service to the engine must be performed by
an authorized HONDA dealer.
1. Remove Pinion Assembly/Clutch Armature/Clamp and
Clutch Housing, as instructed on pages 9, 10 and 11.
2. FIG. 12. Disconnect all necessary wiring.
3. FIG. 13. Remove two locknuts (17) and screws (16) from
base of engine.
4. Lift engine carefully and place on work bench.
FIG. 12
FIG. 13
Installation
1. Lift engine carefully and place on cart.
2. FIG. 13. Install two screws (16) in base of engine and
secure with locknuts (17). Torque to 26 ft-lb (22.6 N·m).
3. FIG. 12. Connect all necessary wiring.
4. Install Pinion Assembly/Clutch Armature/Clamp and
Clutch Housing, as instructed on pages 9 and 10 and 11.
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Pressure Control
310893J 13
Pressure Control
Pump ON/OFF Switch
Removal
1. FIG. 14. Remove two screws (71) and swing down
cover (130a).
2. Disconnect pump ON/OFF switch (130f) connector from
control board.
3. Press in on two retaining tabs on each side of pump
ON/OFF switch (130f) and remove switch from cover.
Installation
1. Install new pump ON/OFF switch (130f) so tabs of switch
snap into place on inside of cover.
2. Connect pump ON/OFF switch connector to control
board.
3. Swing up cover (130a) and secure with two screws (71).
FIG. 14
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4
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Pressure Control
14 310893J
Control Board
Removal
1. FIG. 14. Remove two screws (71) and swing down
cover (130a)
2. Remove strain relief bushings (130r and 123).
3. Disconnect at control board (130b):
• Lead from potentiometer (130d)
• Lead from transducer (66)
• Lead from WatchDog switch (130g)
• Lead from pump ON/OFF switch (130f)
• Lead from gallon counter sensor (39)
• Display connector (130m)
• Engine, ground and clutch wires
4. Remove four screws (130c) and control board (130b).
Installation
1. FIG. 14 . Install control board (130b) with four screws (130c).
2. Connect engine wires to control board (130b).
3. Connect at control board (130b):
• Ground and clutch wires
• Display connector (130m)
• Lead from gallon counter sensor (39)
• Lead from pump ON/OFF switch (130f)
• Lead from WatchDog switch (130g)
• Lead from transducer (66)
• Lead from potentiometer (130d)
4. Install new strain relief bushings (123 and 130r).
5. Swing up cover (130a) and secure with two screws (71).
Pressure Control Transducer
Removal
1. FIG. 14. Remove two screws (71) and swing down
cover (130a)
2. Disconnect transducer (66) lead from control board
(130b).
3. Pull transducer connector through rubber grommet (113).
4. Remove pressure control transducer (66) and o-ring (67)
from filter housing (72).
Installation
1. FIG. 14. Install o-ring (67) and pressure control transducer
(66) in filter housing (72). Torque to 35 - 45 ft-lb.
2. Install transducer connector and rubber grommet in
control housing.
3. Connect transducer (66) lead to control board (130b).
4. Swing up cover (130a) and secure with two screws (71).
Pressure Adjust Potentiometer
Removal
1. FIG. 14. Remove two screws (71) and swing down
cover (130a)
2. Disconnect potentiometer (130d) lead from control board
(130b).
3. Loosen set screws on potentiometer knob (130h) and remove
knob, shaft nut, lock washer and potentiometer (130d).
4. Remove shaft spacer (130e) from potentiometer.
Installation
1. Install shaft spacer (130e) on potentiometer (130d).
2. FIG. 14. Install potentiometer, shaft nut, lock washer and
potentiometer knob (130h).
a.Turn potentiometer shaft clockwise to internal stop.
Assemble potentiometer knob (130h) to strike pin on
cover (130a).
b.After adjustment of step a., tighten both set screws in
knob 1/4 to 3/8 turn after contact with shaft.
3. Connect potentiometer lead to control board (130b).
4. Swing up cover (130a) and secure with two screws (71).
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4

Pressure Control
310893J 15
Digital Display Messages
* Error codes also appear on control board as a blinking red
LED. LED is an alternate to digital messages.
1. Remove two screws (71) and swing down cover (130).
2. Start engine. Blink count is the same as error code(E=0X).
After a fault, follow these steps to restart sprayer:
1. Correct fault condition
2. Turn sprayer OFF
3. Turn sprayer ON
WARNING
Relieve pressure before repair, page 5.
DISPLAY* SPRAYER OPERATION INDICATION ACTION
No Display Sprayer may be pressurized Loss of power or display not
connected
Check power source. Relieve pressure
before repair or disassembly. Verify
display is connected.
Sprayer may be pressurized Pressure less than
200 psi (14 bar, 1.4 MPa)
Increase pressure as needed
Sprayer is pressurized. Power is applied.
(Pressure varies with tip size and
pressure control setting.)
Normal operation Spray
Sprayer stops. Engine is running. Exceeded pressure limit 1. Check fluid path for clogs, such as
clogged filter
2. Open prime valve and gun if running
AutoClean
3. Use Graco paint hose, 1/4 in. x 50 ft
minimum. Smaller hose or metal
braid hose may result in pressure
spikes.
4. Replace transducer if fluid path is not
clogged and proper hose is used.
Sprayer stops. Engine is running. Pressure transducer faulty, bad
connection or broken wire
1. Check transducer connection
2. Disconnect and reconnect
transducer plug to ensure good
connection with control board socket
3. Open prime valve. Replace sprayer
transducer with known good
transducer and run sprayer. Replace
transducer if sprayer runs or control
board if sprayer does not run.
Sprayer stops. Engine is running. High clutch current 1. Check wiring connections.
2.
Measure: 1.2 +0.2 Ω (GMax II 3900);
1.7 +0.2Ω(GMax II 5900/ 7900)
across clutch field at 70°F
3. Replace clutch field assembly
Sprayer stops. Engine is running. Loss of paint to pump or severe
pressure loss
1. Check for empty paint condition, clogged
inlet strainer, failed pump or severe leak
2. Reduce pressure and turn pump
switch OFF and ON to restart pump
3. WatchDog function can be deactivated
by turning WatchDog switch OFF
Sprayer stops. Engine is running. Pressure greater than
2000 psi (138 bar, 14 MPa) while in
Flush Timer Mode
1. Open prime valve and gun
2. Verify no flow obstructions or
clogged filter
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• Blinking LED total count equals digital error code
i.e., two blinks is the same as E=02

Displacement Pump
16 310893J
Displacement Pump
Removal
1. Flush pump.
2. Stop pump with piston rod in its lowest position.
3. Do Pressure Relief, page 5.
4. Separate drain hose from sprayer
FIG. 15
5. Disconnect paint hose from pump.
FIG. 16
6. Raise latch lock. Push latch open.
FIG. 17
7. FIG. 18. Ratchet open pump door.
a. Ratchet pump door forward.
FIG. 18
b. Twist latch u-bolt out of pump door recess.
c. Place u-bolt on pump door outer edge.
d. If pump door is stuck, do steps e., f. and 8., otherwise
go to step 9.
FIG. 19
WARNING
Read Injection Hazard, page 3; Burn Hazard, page 4
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Displacement Pump
310893J 17
e. Twist latch u-bolt back from pump door outer edge
f. Place u-bolt on pump door protrusion
FIG. 20
8. Ratchet pump door forward.
FIG. 21
9. Open pump door.
FIG. 22
10. FIG. 23. Pull out pump pin and place in pin holder
FIG. 23
Installation
1. FIG. 24. Adjust piston rod with pin holder to pull out piston
rod. Tap piston rod on hard surface to push in piston rod.
2. Push pump collar flush with bearing housing ledge to be
able to close pump door.
FIG. 24
3. FIG. 25 . Slide pump into connecting rod. Push pump pin until it
is fully retained.
Note: Pin will snap into position.
FIG. 25
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Displacement Pump
18 310893J
4. FIG. 26. Close pump door and rotate latch into position.
Do not tighten latch.
5. FIG. 26. Rotate pump to align with paint hose. Connect
paint hose and hand tighten to 70 in-lb
FIG. 26
6. FIG. 27 . Tighten latch and rotate latch lock into locked position.
FIG. 27
7. FIG. 28. Attach drain hose to sprayer.
FIG. 28
8. FIG. 29. Fill pump with Graco TSL until fluid flows onto top
of seal.
FIG. 29
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Displacement Pump
310893J 19

Parts
20 310893J
Parts
GMax ll 3900 Parts Drawing
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