Graco GMx 7900 User manual

824128

Rev. E

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PATENTS PENDING

9035A

INSTRUCTIONS-REPAIR

INSTRUCTIONS

KEEP FOR REFERENCE.

Read this and all related manuals for

important warnings and instructions.

GMxr7900

Airless Paint Sprayer

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

GMx 7900

Model Series Description

824630 B Hi-Boy with tool box and Lo-Boy

suction/drain line kit

Table of Contents

Warnings and Cautions 2. . . . . . . . . . . . . . . . . . . . . . . . .

Component Identification and Function 3. . . . . . . . . . . .

Maintenance 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Troubleshooting 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Repair

Rollers 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Drive Housing 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cam Follower Bearings 8. . . . . . . . . . . . . . . . . . . . . . .

Pinion Assembly/Rotor/Field/Shaft/Clutch 9. . . . . . . .

Clamp 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Clutch Housing 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Engine 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pressure Control 13. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Displacement Pump 15. . . . . . . . . . . . . . . . . . . . . . . . .

Parts

Pinion Assembly 17. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sprayer 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pressure Control 20. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lo-Boy Suction Set Kit 22. . . . . . . . . . . . . . . . . . . . . . .

Dimensions 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Technical Data 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Phone Number 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sherwin-Williams Warranty 24. . . . . . . . . . . . . . . . . . . . .

The SHERWIN–WILLIAMS COMPANY, CLEVELAND, OHIO 44115

8241282

Warnings and Cautions

Warning Symbol

WARNING

This symbol alerts you to the possibility of serious

injury or death if you do not follow the instructions.

Caution Symbol

CAUTION

This symbol alerts you to the possibility of damage to

or destruction of equipment if you do not follow the

instructions.

Fluid injection is a serious injury! If high pressure fluid pierces

your skin, the injury might look like “just a cut”. But it is a serious

wound! Get immediate medical attention.

To help prevent injection, always:

DEngage trigger safety latch when not spraying.

DPoint gun away from yourself or anyone else.

DRelieve pressure before checking or repairing any leak.

DRelieve pressure when you turn off the sprayer or stop spraying.

DDo not use components rated less than system Maximum

Working Pressure

Never allow children to use this unit. If you are injured using this

equipment, get immediate medical treatment.

Fire and explosion can occur when spraying or flushing flammable

fluid in an area where air circulation is poor and flammable vapors

can be ignited by an open flame or sparks.

To help prevent a fire and explosion:

DUse outdoors or in an extremely well ventilated area.

DDo not use 1,1,1–trichloroethane, methylene chloride, other

halogenated hydrocarbon solvents or fluids containing such

solvents in pressurized aluminum equipment. Such use could

result in a chemical reaction, with the possibility of explosion.

DRemove, extinguish or unplug all ignition sources;

tape wall switch. Do not smoke in spray area.

DNever fill fuel tank while the engine is running or hot.

DGround Sprayer, object being sprayed, paint and solvent pails.

DHold gun firmly to side of a grounded pail when triggering into pail.

DUse only conductive airless paint hose.

DNever run engine in inclosed area.

WARNING

824128 3

Component Identification and Function

9034A

Fig. 1

Model 824630

APressure Control Switch ON/OFF, enables/disables clutch function and pressure control

BPressure Adjusting Knob Controls fluid outlet pressure

CAir Cleaner* Filters air entering the carburetor

DFuel Tank* Uses 86 octane unleaded gasoline

EMuffler* Reduces noise of internal combustion

FSpark Plug Cable* Routes electrical current to spark plug

GFuel Shutoff Lever* On/off lever to regulate fuel flow from gasoline tank to carburetor

HChoke* Enriches air/gasoline mixture for cold starting

JThrottle Lever* Adjusts engine speed for large or small orifice spray tips

KEngine Switch* Enables/disables engine operation

LSecondary Fluid Outlet Second hose and spray gun is connected here

MPressure Control Controls clutch cycling to maintain fluid pressure.

NPrimary Fluid Outlet Hose and spray gun is connected here

PEngine* 4–cycle gasoline engine

RClutch Housing Transfers power from engine to drive assembly

SDrive Housing Transfers power from clutch to displacement pump

TDisplacement Pump Provides fluid to be sprayed through spray gun

UFluid Filter Filters fluid between source and spray gun

VGrounding Clamp and Wire Grounds sprayer system

WPail Hanger Provides a hanger for paint pail

XDrain Valve Relieves fluid pressure when open

*For more detailed explanations of these controls, refer to the Honda Engines Owner’s Manual; supplied

8241284

Maintenance

WARNING

INJECTION HAZARD

The system pressure must be manually

relieved to prevent the system from

starting or spraying accidentally. Fluid

under high pressure can be injected through the

skin and cause serious injury. To reduce the risk of

an injury from injection, splashing fluid, or moving

parts, follow the Pressure Relief Procedure

whenever you:

Dare instructed to relieve the pressure,

Dstop spraying,

Dcheck or service any of the system equipment,

Dor install or clean the spray tip.

Pressure Relief Procedure

1. Lock gun trigger safety.

2. Turn engine ON/OFF switch to OFF.

3. Move pressure control 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.

CAUTION

For detailed engine maintenance and specifications,

refer to separate Honda Engines Owner’s Manual,

supplied.

DAILY: Check engine oil level and fill as necessary.

DAILY: Check hose for wear and damage.

DAILY: Check gun safety for proper operation.

DAILY: Check pressure drain valve for proper opera-

tion.

DAILY: Check and fill the gas tank.

AFTER THE FIRST 20 HOURS OF OPERATION:

Drain engine oil and refill with clean oil. Reference

Honda Engines Owner’s Manual for correct oil viscos-

ity.

WEEKLY: Remove air filter cover and clean element.

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.

WEEKLY: Check level of TSL in displacement pump

packing nut. Fill nut, if necessary. Keep TSL in nut to

help prevent fluid buildup on piston rod and premature

wear of packings.

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.

824128 5

Troubleshooting

WARNING

INJECTION HAZARD

To reduce risk of serious injury, including fluid injection or splashing in eyes or on skin, or injury from

moving parts, always follow Pressure Relief Procedure Warning, page 4, before checking, adjust-

ing, cleaning or shutting down sprayer.

PROBLEM CAUSE SOLUTION

Engine won’t start Engine switch is OFF Turn engine switch ON

Engine is out of gas Refill gas tank. Honda Engines Owner’s Manu-

al.

Engine oil level is low Try to start engine. Replenish oil, if necessary.

Honda Engines Owner’s Manual.

Spark plug cable 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 rope 3 or 4

times. Clean or replace spark plug. Try to start

engine. Keep sprayer upright to avoid oil seep-

age.

Engine operates, but dis-

lacement

does not

Pressure control switch is OFF Turn pressure control switch ON.

acemen

pump

oes no

operate Pressure setting is too low Turn pressure adjusting knob clockwise to

increase pressure.

Fluid filter (318) is dirty Clean filter. Page 20.

Tip or tip filter is clogged Clean tip or tip filter. Manual 307614.

Displacement pump piston rod is stuck due to

dried paint

Repair pump. Manual 308798.

Roller bearings are worn or damaged Replace connecting rod. Page 7.

Drive housing is worn or damaged Replace drive housing. Page 7.

Electrical power is not energizing clutch field Check wiring connections. Page 11.

Reference control board diagnostics. Page 14.

With pressure control switch ON and pressure

turned to MAXIMUM, use a test light to check

for power between clutch terminals on control

board.

Remove black clutch wires from control board

and measure resistance across wires. At 70_

F, the resistance must be between 1.7 ±0.2Ω; if

not, replace clutch coil 241121.

Have pressure control checked by authorized

Graco dealer.

Clutch is worn or damaged Replace clutch. Page 9.

Pinion assembly is worn or damaged Repair or replace pinion assembly. Page 9.

8241286

PROBLEM CAUSE SOLUTION

Pump output is low Strainer (31) is clogged Clean strainer

Piston ball (25) is not seating Service piston ball. Manual 308798.

Piston packings are worn or damaged Replace packings. Manual 308798.

O-ring (227) in displacement pump is worn or

damaged

Replace o-ring. Manual 308798.

Intake valve ball is not seating properly Clean intake valve. manual 308798.

Engine speed is too low Increase throttle setting. Manual 308867.

Clutch is worn or damaged Replace clutch. Page 9.

Pressure setting is too low Increase pressure. Manual 308867.

Fluid filter (318), tip filter or tip is clogged or

dirty

Clean filter. Manual 308867 or 307614.

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 perfor-

mance (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 leakage.

Throat packings are worn or damaged Replace packings. Manual 308798.

Displacement rod is worn or damaged Replace rod. Manual 308798.

Fluid is spitting from gun Air in pump or hose Check and tighten all fluid connections.

Reprime pump. Manual 308867.

Tip is partially clogged Clear tip. Manual 307614.

Fluid supply is low or empty Refill fluid supply. Prime pump. Manual

308867. 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. Reas-

semble valve.

Pump packings are worn Replace pump packings. Manual 308798.

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 308867.

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

Engine stalls Engine speed is to slow DIncrease throttle setting

DAdjust engine speed at no load to 3750 –

3850 rpm

Fluid filter is clogged Relieve pressure and clean filter

Too much pump friction (new pump) Reduce pressure to 3000 psi until pump wears

Spark plug wire is loose Reconnect wire

824128 7

Rollers

Removal

1. Relieve pressure;page 4.

2. Fig. 2. Remove six cap screws (10) lock washers

(9) and cover assembly (24).

Note: A screw driver may be needed to pry off

cover assembly.

3. Remove dowel pins (97) and rollers (98)

Installation

1. Install rollers (98) and dowel pins (97)

2. Install cover assembly (24) with six lock washers

(9) and cap screws (10). Fig. 2

9033A

Drive Housing

Removal

1. Relieve pressure;page 4.

2. Fig. 2. Remove six cap screws (10) lock washers

(9) and cover assembly (24).

3. Fig. 3. Remove two screws (99) and washers (9).

4. Remove four cap screws (10) lock washers (9)

from drive housing (20).

5. Lightly tap around drive housing (20) to loosen

drive housing. Pull drive housing straight off pinion

housing. Be prepared to support gear cluster (18),

which may also come out.

Fig. 3 9032A

20h

20g

82 83

1Apply remaining grease to these areas

Installation

1. Liberally apply bearing grease (supplied with

replacement gear cluster) to gear cluster (18),

washers (82) and (83) and to areas called out by

note 1. Use full 0.68 pint (0.32 liter) of grease for

GMx 7900.

2. Place bronze colored washer (83) and silver

colored washer (82) onto drive housing (20). Install

gear cluster (18) through washers (83) and (82).

3. Place bronze colored washer (20g) and silver

colored washer (20h) on shaft protruding from

large shaft of drive housing (20). Align gears and

push new drive housing straight onto pinion hous-

ing and locating pins (B).

4. Install two washers (9) and screws (99).

5. Install four lock washers (9) and cap screws (10)

into drive housing (20).

6. Install cover assembly (24) with six lock washers

(9) and cap screws (10).

8241288

Cam Follower Bearings

Removal

1. Relieve pressure;page 4.

2. Fig. 16. Cycle pump piston rod (222) to lowest

position. Turn engine off.

3. Fig. 4. Remove six cap screws (10), lock washers

(9) and cover assembly (24).

Note: A screw driver may be needed to pry off

cover assembly.

4. Remove four dowel pins (97) and rollers (98).

5. From front, drive out pump pin (101) with a screw

driver.

6. Remove two retainer rings (20d).

7. Remove cam follower plate (20b).

Note: Two 1/2 in. x 13 bolts may be

needed to remove cam follower plates.

8. Remove two cam follower bearings (20c).

Installation

1. Install two cam follower bearings (20c).

2. Install cam follower plate (20b).

3. Install two retainer rings (20d).

4. Drive in pump pin (101) until it engages with pump

pin retaining clip (20a).

5. Install four rollers (98) and dowel

pins (97).

6. Install cover assembly (24) with six lock washers

(9) and cap screws (10).

Fig. 4

9047A

101

20c

20b

20d

20a

824128 9

Pinion Assembly/Rotor/Field/Shaft/Clutch

Removal

If pinion assembly (19) is not removed from clutch

housing (5), do 1. through 4. Otherwise, start at 5.

1. Relieve pressure;page 4.

2. Disconnect field cable (X) from pressure control

and engine lead.

9027A

Fig. 5

Bottom View

3. Fig. 6. Remove five screws (26) and lockwashers

(17) and pinion assembly (19).

Fig. 6 9029A

4. Fig. 7. Place pinion assembly (19) on bench with

rotor side up.

5. Remove four screws (72) and lockwashers (17).

Install two screws in threaded holes (E) in rotor.

Alternately tighten screws until rotor comes off.

Fig. 7

9030A

6. Fig. 8. Remove retaining ring (19e).

7. Tap pinion shaft (19d) out with plastic mallet.

Fig. 8

19e

19d

9030A

8. Fig.9. Use an impact wrench or wedge something

between armature (4a) and clutch housing to hold

engine shaft during removal.

9. Remove four screws (16) and lockwashers (17).

10. Remove armature (4a).

Fig. 9

9028A

82412810

Pinion Assembly/Rotor/Field/Shaft/Clutch

Installation

1. Fig. 10. Lay two stacks of two dimes on smooth

bench surface.

2. Lay armature (4a) on two stacks of dimes.

3. Press center of clutch down on bench surface.

Fig. 10

8705A

0.12 ±.01 in. (3.0 ±.25 mm)

4. Install armature (4a) on engine drive shaft.

5. Install four screws (16) and lockwashers (17) with

torque of 125 in-lb.

6. Fig. 8. Tap pinion shaft (19d) in with plastic mallet.

7. Install retaining ring (19e) with beveled side facing

field (Y).

8. Fig. 7. Place pinion assembly on bench with rotor

side up.

9. Apply locktite to screws. Install four screws (16)

and lockwashers (17). Alternately torque screws

to 125 in-lb until rotor is secure. Use threaded

holes to hold rotor.

10. Fig. 6. Install pinion assembly (19) with five screws

(10) and lockwashers (9).

11. Fig. 5. Connect field cable (X) to pressure control

and engine lead.

Clamp

Removal

1. Fig. 11. Loosen two screws (16) on clamp (8),

2. Push screwdriver into slot in clamp (8) and remove

clamp.

Installation

1. Fig. 11. Install engine shaft key (7).

2. Tap clamp (8) on engine shaft (A) with plastic

mallet.

3. Press clamp (8) onto engine shaft (A). Maintain

dimension shown note 2 in Fig. 11. Chamfer side

must face engine.

Check dimension: Place rigid, straight steel bar (B)

across face of clutch housing (5). Use accurate

measuring device to measure distance between

bar and face of clamp. Adjust clamp as necessary.

Torque two screws (16) to 125 ±10 in-lb (14 ±1.1

Nm). Fig. 11

03483

Face of clutch housing

1.812 ±.010 in. (46.02 ±.25 mm)

Torque to 125 ±.10 in-lb (14 ±1.1 Nm)

4Chamfer this side

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