General Pump Pressure Washer System Manual

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INSTALLATION
OPERATION
SERVICE
MANUAL
TABLE OF CONTENTS
Introduction ..........................................................2 Selecting Remaining Components . . . . . . 6 - 7
Typical Operation & Requirements .......................2 Upstream or Inlet Side
Pressure.........................................................2 Components . . . . . . . . . . . . . . . . . . . 6
Flow................................................................2 Downstream or Outlet Side
Designing Your System ...................................3 - 5 Components . . . . . . . . . . . . . . . . 6 - 7
Pump Selection ..............................................3 Installing Your Components . . . . . . . . . . . 7 - 8
Motor/Engine Selection ..................................3 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . 9
Determining Spray Tip Size............................5 Servicing Your Pump. . . . . . . . . . . . . . . 10 - 11
Drive System ...................................................5 - 6 Valve Assemblies. . . . . . . . . . . . . . . . . . 10
Pulley Selection..............................................5 Removing Manifold ead . . . . . . . . . . . 10
Belt Selection .................................................6 Replacing Plungers . . . . . . . . . . . . . . . . 11
Replacing Packings . . . . . . . . . . . . . . . . 11

INTRODUCTION
Thank you for purchasing a GENERAL PUMP Pressure
Washer Pump. With proper installation and maintenance
it will provide you with many years of dependable,
trouble-free service.
This manual was developed as a basic guide to
understanding the operation and requirements,
installation, and servicing of GENERAL PUMP positive
displacement pumps.
Pressure cleaning equipment is potentially hazardous
and could cause personal injury or property damage if
installed, repaired, or operated in an unsafe manner, or in
a manner which is not consistent with the manufacturer’s
recommendations or requirements.
There are many manufacturers of pressure washer
pumps and complementary components. Be sure that the
required components you choose to use are consistent
with the high quality standards of GENERAL PUMP
pumps.
GENERAL PUMP does not assume liability or
responsibility for the design of a customer’s high
pressure system.
TYPICAL OPERATION AND
REQUIREMENTS
PRESSURE
The pressure produced in a pressure washer
system is the result of forcing a known volume
(or flow) of water through a known size orifice
(spray tip). Pressure is measured in pounds per
square inch (PSI).
FLOW
The flow or volume produced in a pressure washer
system is determined by the speed that the pump
shaft is rotated (RPM). The faster the shaft is
rotated, the higher the output volume. Flow or
volume is measured in gallons per minute (GPM).
The pump, which is driven by an electric motor or a gas
engine, draws or accepts filtered water in through a se-
ries of inlet check valves as the plungers move back. As
the plungers move forward, the inlet valves close, forcing
the water to travel through a series of outlet check valves,
and to the outbound side of the pump.
After the water exits the pump, its flow direction must be
controlled with an unloading or regulating valve. A
positive displacement pump is always delivering a
certain volume of water whether the spray gun is open
or closed, therefore a device is needed to control the di-
rection of flow, either allowing the flow to go through the
open spray gun, or redirecting (by-passing) the flow back to
the inbound side of the pump when the spray gun is closed.
Without an unloading or regulating valve, dangerously high
pressures will be produced when the spray gun is closed
because the water being forced out of the pump has no
place to go. Serious bodily injury or property damage could
be caused by failure to properly utilize an appropriate un-
loader or regulator valve in your pressure washer system.
As a safety device, at least one pressure relief valve should
be installed in the outbound side of the pump to guard
against failure of component parts, and the development of
dangerously high pressures.
Cleaning chemicals or detergents may be introduced into
the flow of water either inbound or outbound of the pump.
An inbound or upstream type of chemical injector simply
uses the pump’s ability to draw or suck fluid in to introduce
a chemical into the stream of water. Care must be taken to
avoid introducing any chemicals which are not compatible
with the materials in the pump and downstream compo-
nents. An upstream injector does allow chemicals to be ap-
plied to the work surface at the normal high working
pressure of the system. An outbound or downstream type of
chemical injector uses a venturi (very similar to that used in
an automotive carburetor) to draw a chemical into the water
stream. A downstream injector requires low pressure to ac-
tivate chemical flow. Low pressure is achieved by chang-
ing to a large sized spray tip, or opening up a large orifice
at the outlet end of the spray gun using an adjustable noz-
zle or a double lance. There are several advantages to
using a downstream injector over using an upstream type.
1. Fewer component parts are exposed to the cleaning
chemicals, extending system life.
2. The operator can control the flow of chemical (on and
off) by changing the system pressure at the nozzle.
3. Applying chemical at low pressure is more
economical because less chemical bounces off the
work surface.
eated pressure washers and steam cleaners increase
the ability of a high pressure flow of water to break down
dirt and grease. They also increase the action of most
cleaning chemicals. These systems are very comples,
and add more potential personal injury and property
damage hazards. Design of these systems requires many
more additional components as well as experienced de-
sign personnel with knowledge of fuels, heat transfers,
electronics, etc.
2

TYPICAL PRESSURE WASHER SYSTEM
WANDSPRAY GUN SPRAY TIP
HIGH
PRESSURE
HOSE
CHEMICAL
INJECTOR
UNLOADER OR
REGULATOR VALVE
PRESSURE
GAUGE
PRESSURE
RELIEF VALVE
PULSATION
DAMPENER
PUMP
THERMAL
RELIEF
VALVE
FLUID
BY-PASS
HOSE
INLET FILTER
POWER SOURCE
(MOTOR/ENGINE)
Drive
System
3
DESIGNING
YOUR SYSTEM
PUMP SELECTION
The heart of any pressure washer system is the high
pressure pump. Size the pump according to your clean-
ing needs. igher than required pressure and volume will
cause needless wear of all components in the system,
and could actually damage your work surface instead of
cleaning it. Never exceed the maximum pressures of ro-
tation speed as is stated on the Technical Data Sheet
supplied with each pump.
Refer to the Pump Data Sheet to determine what pump
RPM is needed to deliver your required GPM output.
MOTOR/ENGINE SELECTION
The size of the electric motor or gas engine required to
drive your pump is determined by the pump GPM and
PSI output desired. Refer to the Technical Data Sheet
supplied with each pump, or the following chart. Both
charts are based on electric horsepower requirements;
for gas engines multiply by 1.8. Gas engine output
horsepower varies with running RPM. Be sure to run a
gas engine fast enough to supply required horsepower,
but do not exceed manufacturer’s specifications.

4
ELECTRIC MOTOR HORSEPOWER REQUIRED TO DRIVE A PUMP
GPM 100 PSI 200 PSI 250 PSI 300 PSI 400 PSI 500 PSI 700 PSI 1000 PSI 1250 PSI 1500 PSI 2000 PSI 2500 PSI 3000 PSI 4000 PSI
.5 .04 .07 .09 .11 .14 .18 .26 .35 .44 .53 .70 .88 1.10 1.40
1.0 .07 .14 .18 .21 .28 .35 .52 .70 .88 1.05 1.40 1.76 1.92 2.80
1.5 .10 .21 .26 .31 .41 .52 .77 1.03 1.29 1.55 2.06 2.58 3.09 4.12
2.0 .14 .28 .35 .42 .56 .70 1.04 1.40 1.76 2.10 2.80 3.53 4.20 5.60
2.5 .17 .34 .43 .51 .69 .86 1.29 1.72 2.15 2.58 3.44 4.30 5.14 6.88
3.0 .21 .42 .53 .63 .84 1.05 1.56 2.10 2.64 3.15 4.20 5.28 6.30 8.40
3.5 .24 .48 .60 .72 .96 1.20 1.80 2.40 3.00 3.60 4.80 6.00 7.20 9.60
4.0 .28 .56 .70 .84 1.12 1.40 2.08 2.80 3.52 4.20 5.60 7.04 8.40 11.20
5.0 .35 .70 .88 1.05 1.40 1.75 2.60 3.50 4.40 5.25 7.00 8.80 10.50 14.00
6.0 .42 .84 1.05 1.26 1.68 2.10 3.12 4.20 5.28 6.30 8.40 10.56 12.60 16.50
7.0 .49 .98 1.23 1.47 1.96 2.45 3.64 4.90 6.16 7.35 9.80 12.32 14.70 19.60
8.0 .56 1.12 1.40 1.68 2.24 2.80 4.16 5.60 7.04 8.40 11.20 14.08 16.80 22.40
9.0 .62 1.24 1.55 1.86 2.48 3.10 4.65 6.18 7.73 9.28 12.40 15.56 18.58 24.80
10.0 .70 1.40 1.75 2.10 2.80 3.50 5.20 7.00 8.80 10.50 14.00 17.60 21.00 28.00
*Tip
Size
Orifice Dia.
(Inches)
OUTPUT VOLUME (GPM) AT VARIOUS PRESSURES (PSI)
40 PSI 100 PSI 250 PSI 500 PSI 600 PSI 700 PSI 800 PSI 1000 PSI 1200 PSI 1500 PSI 2000 PSI 2500 PSI 3000 PSI 3500 PSI 4000 PSI
2 .034 .20 .32 .50 .71 .77 .80 .89 1.0 1.1 1.2 1.4 1.6 1.7 1.9 2.0
4 .052 .40 .63 1.00 1.40 1.60 1.70 1.80 2.0 2.2 2.5 2.8 3.1 35. 3.8 4.0
4.5 .055 .45 .71 1.10 1.50 1.70 1.90 2.00 2.2 2.4 2.8 3.0 3.6 3.9 4.3 4.5
5 .057 .50 .79 1.30 1.80 1.90 2.10 2.20 2.5 2.8 3.1 3.6 4.0 4.4 4.7 5.0
5.5 .060 .55 .87 1.40 1.90 2.10 2.30 2.50 2.8 3.0 3.4 3.8 4.4 4.8 5.2 5.5
6 .062 .60 .95 1.50 2.10 2.30 2.50 2.70 3.0 3.2 3.7 4.2 4.8 5.2 5.6 6.0
6.5 .064 .65 1.00 1.70 2.30 2.50 2.70 2.90 3.3 3.6 4.0 4.6 5.2 5.7 6.0 6.5
7 .067 .70 1.10 1.80 2.50 2.70 2.90 3.10 3.5 3.8 4.3 5.0 5.6 6.1 6.6 7.0
7.5 .707 .75 1.20 1.90 2.70 2.90 3.20 3.40 3.8 4.1 4.6 5.3 6.0 6.5 7.0 7.5
8 .072 .80 1.30 2.00 2.80 3.10 3.40 3.60 4.0 4.4 5.0 5.6 6.2 7.0 7.5 8.0
8.5 .074 .85 1.30 2.20 3.00 3.30 3.60 3.80 4.3 4.6 5.3 6.0 6.7 7.4 8.0 8.5
9 .076 .90 1.40 2.30 3.20 3.50 3.80 4.00 4.5 5.0 5.5 6.4 7.1 7.8 8.5 9.0
9.5 .078 .95 1.50 2.40 3.40 3.70 4.00 4.30 4.8 5.2 5.8 6.8 7.6 8.3 9.0 9.5
10 .080 1.00 1.60 2.50 3.50 3.90 4.20 4.50 5.0 5.4 6.1 7.0 8.0 8.7 9.4 10.0
12 .087 1.20 1.90 3.00 4.20 4.60 5.00 5.40 6.0 6.4 7.3 8.4 9.5 10.4 11.2 12.0
15 .094 1.50 2.40 3.80 5.30 5.80 6.40 6.80 7.5 8.2 9.2 10.6 12.0 12.9 14.0 15.0
20 .109 2.00 3.20 5.00 7.10 7.80 8.40 9.00 10.0 10.8 12.2 14.2 16.0 17.4 18.8 20.0
30 .141 3.00 4.70 7.50 10.60 11.60 12.80 13.60 15.00 16.40 18.40 21.2 24.0 26.0 28.0 30.0
40 .156 4.00 6.30 10.00 14.20 15.60 16.80 18.00 20.00 21.60 24.40 28.4 32.0 34.8 37.6 40.0
SPRAY TIP SELECTION CHART
NOTES: 1, A gasoline engine should be sized 1.8 times the electric horsepower requirement.
2. Always select a motor/engine with a horsepower rating above the minimum requirements shown
above. Example: 5.0 GPM - 1250 PSI is 4.40 mi imum electric horsepower requireme t, use a
5 horsepower electric motor.
If you wish to direct drive your pump from an electric
motor, you may want to use a “C” face motor.
Check with your motor supplier for technicla
information.
* A commonly used standard for tip size is the “nozzle number” which is equivalent to the nozzle
capacity in GPM at 4000 PSI. Spray angle does not affect nozzle volume.

Pump Pulley
Outside Diameter
(inches)
MOTOR PULLEY OUTSIDE DIAMETER (inches)
2-1/2 2-3/4 3 3-1/4 3-1/2 3-3/4 4 4-1/4 4-1/2 4-3/4 5 5-1/4 5-1/2 5-3/4 6 6-1/2 7 8 9 10 11 12 13 14
2-1/2 1725
2-1/4 1574 1725
3 1431 1590 1725
3-1/4 1310 1460 1604 1725
3-1/2 1210 1346 1480 1615 1725
3-3/4 1125 1250 1375 1500 1625 1725
4 1050 1168 1283 1400 1518 1634 1725
4-1/4 985 1094 1201 1311 1420 1530 1640 1725
4-1/2 926 1030 1131 1235 1339 1440 1543 1650 1725
4-3/4 876 974 1070 1168 1285 1362 1460 1558 1652 1725
5 830 922 1013 1105 1198 1290 1382 1473 1568 1660 1725
5-1/4 788 875 963 1050 1137 1225 1312 1400 1487 1575 1662 1725
5-1/2 750 834 917 1000 1082 1167 1250 1333 1417 1500 1581 1646 1725
5-3/4 715 795 875 955 1032 1113 1192 1270 1350 1430 1510 1575 1650 1725
6 685 760 937 913 990 1065 1140 1217 1290 1370 1450 1509 1581 1653 1725
6-1/2 630 700 771 840 910 980 1050 1120 1190 1260 1330 1393 1460 1526 1592 1725
7 584 648 713 778 843 907 973 1039 1102 1168 1231 1294 1355 1417 1500 1602 1725
8 507 564 620 676 734 789 845 902 959 1016 1072 1132 1186 1240 1312 1421 1509 1725
9 450 500 550 600 650 700 750 800 850 900 950 1006 1054 1102 1166 1263 1342 1533 1725
10 405 450 495 540 585 630 675 720 765 810 855 906 949 992 1050 1137 1208 1380 1553 1725
11 366 407 448 488 530 570 610 652 692 733 774 823 863 902 954 1034 1098 1255 1411 1568 1725
12 336 373 410 446 485 522 560 596 634 671 708 755 791 827 875 947 1006 1150 1294 1438 1581 1725
13 309 343 378 412 447 480 515 549 584 618 652 697 730 763 807 875 929 1062 1194 1327 1460 1592 1725
14 286 318 350 382 414 445 477 509 540 573 605 647 678 708 750 813 863 986 1109 1232 1355 1479 1602 1725
15 267 297 326 358 386 415 445 475 505 534 564 604 633 661 700 758 805 920 1035 1150 1265 1380 1495 1610
16 250 278 306 333 361 389 416 445 473 500 528 566 593 620 656 711 755 863 970 1078 1186 1294 1402 1509`
DETERMINING SPRAY TIP SIZE
As stated earlier in this manual, the output pressure is
determined by forcing the output volume of water
through a certain size orifice or spray tip. Spray tip
size is a very important factor of proper pressure
washer performance, using a tip that is sized too
small will allow overpressurization of the pump and
components. You must know your output GPM and
your desired output PSI to properly select a spray tip
size. To use the chart on page 4, find the desired PSI,
read down the column until you find the output GPM
closest to your pump application. Read to the far left to
find the spray tip number and orifice diameter. Example:
1000 PSI at 4.0 GPM eeds a umber 8 spray tip.
Spray tips are available in various spray angles. It is
advisable to have different spray angle tips in the same
size for different cleaning applications. Some spray
tips or nozzles are available with an adjustable spray
angle.
DRIVE SYSTEM
There are three common methods of driving or
connecting the pump and motor/engine. Direct
drive and gear reductions drive require special
components that are matched to the pump and to the
motor.engine, as well as other technical
considerations. A belt and pulley system is the
recommended method of driving the pump because
it allows easy reduction of the motor/engine RPM
to your required pump RPM, as well as absorbing
shocks produced by both the engine and the pump.
5
PULLEY SELECTION
There are many types of belts and pulleys available,
the following is a basic guide. Manufacturer’s
representatives should be consulted concerning your
specific requirements.
From the Motor Pulley Guide (below) determine the
pulley size (A, B or C section), and number and size
(A, B or C section) of belt required. the larger in size
and/or number of belts used will increase the life
of belts. Be sure to consider space limitations of your
finished assembly.
To determine pump pulley size (based on a 1725
RPM motor), find the motor pulley size on the chart
below, follow the column down until you find your
required Pump RPM to meet your requirements, or
the next higher RPM. Follow the column to the left to
find pump pulley diameter.
To Transmit:
HORSEPOWER
“A” SECTION BELT “B” SECTION BELT “C” SECTION BELT
1 Belt
Single
Groove
Pulley
2 Belts
Double
Groove
Pulley
1 Belt
Single
Groove
Pulley
2 Belts
Double
Groove
Pulley
1 Belt
Single
Groove
Pulley
1 2-1/2 Dia - - - -
1-1/2 3 - - - -
2 3-1/4 - - - -
3 3-3/4 3 Dia 4-1/2 Dia 3-1/2 Dia -
5 5-1/4 3-1/2 5 5 -
7-1/2 - 4-1/2 66 5 -
10 - 5-1/4 8 5 8 Dia
15 - 7 10 6 9
20 - 9 - 7 10
MOTOR PULLEY GUIDE
PUMP PULLEY GUIDE (1725 RPM Motor)

6
If your motor/engine will be operated at a speed
other than 1725 RPM, the pump pulley diameter can
be calculated using the following formula:
Example: Usi g a 1200 RPM motor, a d a pump that
you wa t to tur at 850 RPM for your desired GPM
output, a d you have chose a 4-1/2” diameter motor
pulley.
1.412 x 4.5 = 6.39 actual pump pulley diameter.
There may not be a pulley available in the exact size as
calculated. Simply use the closest one.
BELT SELECTION
Be sure to use the same section belts (A, B or C) as the
pulleys were sized for.
Use the following formula to calculate belt length.
Where: L = Effective outside length of belt(s) in
inches.
C = Distance between centers of pulleys
in inches.
D = Outside diameter of pump pulley in
inches.
d = Outside diameter of motor/engine in
inches.
Always install a safety cover or guard over belt and
pulleys to avoid serious bodily injury or property
damage.
SELECTING REMAINING
COMPONENTS
UPSTREAM OR INLET SIDE COMPONENTS
Inlet Filter - A very important component to increase
system life and avoid operating problems. A 60 - 120
mesh screen filter is necessary to stop foreign matter
from entering the system and possibly holding valves
open, clogging orifices, scratching plungers, tearing
packing, and causing unnecessary wear on all
components.
By-pass Provision - As mentioned earlier in this manual,
the unloader or regulator valve by-passes or recirculates
pumped water when the gun trigger is released. A
provision must be made in the inlet plumbing (or inlet
water holding tank) to accept this flow of water without
restricion.
Thermal Relief Valve - This is a temperature sensing
valve that opens and dumps water to the atmosphere
at a predetermined temperature. Recirculating water
(through the by-pass loop) has a tendency to heat up
to temperatures that can eventually damage internal
pump parts. A thermal relief valve is an inexpensive way
to avoid costly repairs.
Upstream Injector - A device which uses the pumps
ability to draw or suck fluid to introduce a cleaning
chemical into the water stream. This type of injector is
recommended for very mild chemicals only as the entire
system (especially the pump) is exposed to the
corrosive tendencies of the cleaning chemicals.
Pressure Reducing Valve - If the water supply entering
the pump is above maximum inlet pressure rating called
out on the Pump Data Sheet. A pressure reducing valve
must be installed for proper pump operation.
Back-Flow Preventer - When using cleaning chemicals,
care must be taken to avoid these chemicals fom being
back-flushed and contaminating the city water supply.
Check your local plumbing codes. An alternative option
to a “back-flow preventer” is the use of a water holding
tank. If a holding tank is used, be sure not to exceed
the negative pressure rating of the pump.
DOWNSTREAM OR OUTLET SIDE
COMPONENTS
Unloader or Regulator Valve - As mentioned earlier,
this device is required to direct the constant flow of water
either through the spray tip when the gun is open, or by-
pass the flow back to the inlet side of the pump when the
gun is closed. Be sure to adhere to manufacturer’s re-
quirements when selecting, installing, setting-up and
RPM
Ration X
Motor
Pulley
Diameter
X
Pump
Pulley
Diameter
1200
850 = 1.412 RPM Ratio
L = 2(c) + 1.57 (D + d) + (D - d)2
4C

WATER
FLOW
GAL/MIN
PRESSURE DROP IN PSI PER 100 FT OF HOSE
WITH TYPICAL WATER FLOW RATES
( OSE INSIDE DIAMETERS, INC ES)
1/4 5/16 3/8 1/2 5/8 3/4 1”
0.5 16 5 2
1 54 20 7 2
2 180 60 25 6 2
3 380 120 50 13 4 2
4 220 90 24 7 3
5 320 130 34 10 4
6 220 52 16 7 1
8 300 80 25 10 2
10 120 38 14 3
15 250 80 30 7
20 121 50 12
25 200 76 19
40410 162 42
60 370 93
servicing unloader valves. The valve should be mounted
as close to the pump outlet as possible; do not use any
hose between the pump and the unloader.
Pressure Relief Valve - A safety device which when
installed and set-up according to the manufacturer’s
specifications will open and dump to atmosphere a
quantity of water if the system becomes overpressurized
due to a failure of system components.
Pulsation Dampener - Pulsation Dampeners are
installed in systems either to smooth out the pulsations
caused by the pump itself or to absorb pressure spikes
when the gun is shut off. A duplex pump may require a
pulsation dampener because of the pulsation not
experienced with a triplex pump. When there are long
runs of pipe, a pulsation dampener may be required to
soften the hammer effect when a gun is shut off.
Pressure Gauge - Allows the equipment operator to
monitor the system for peak performance. A worn spray
tip will be evident with a decrease in system pressure.
igh pressure may indicate a partially plugged spray tip
or other restriction, or a defect in the unloader valve.
Important factors in gauge selection:
• Liquid filled - to absorb the pressure fluctuations
in the system.
• Restriction orifice installed to avoid damage from
pressure “spikes”.
• Select a gauge so that normal system operating
pressure is in the middle of the gauge’s range.
Downstream Injector - Introduces a cleaning chemical
into the water stream after or downstream of the pump.
Care must be taken to size the injector to the system
volume or GPM. Check with manufacturer’s literature.
Too small of an injector causes a large pressure drop
across the injector and injects a very high concentration
of chemical. Too large of an injector will not draw any
chemical. Downstream injectors require low pressure,
generally about 200 PSI, to activate the chemical flow.
A double nozzle holder, rollover nozzle, and a double
lance are a few accessories that allow mounting a low
pressure spray tip, as well as the standard high pressure
spray tip. An adjustable nozzle allows a large orifice to
be opened around the high pressure spray tip.
High Pressure Hose - A required component of your
system. Be sure that the hose that you select to use is
compatible with all chemicals that will be introduced
into the system, is rated at least 50% greater
than the system operating pressure, has
good quality Permanite couplings on each end (do
not use hose clamps), and is as short as
possible to avoid pressure accumulation when
releasing trigger, and to minimize operating
pressure loss in hose.
7
If quick disconnect couplings are used on the ends of
the high pressure hose, be sure that they are of the
“straight through” design. Air type quick couplers with
internal “shut-offs” are not acceptable because
pylsations in the water flow will destroy the moving parts
and lodge them in the gun and/or spray tip.
Spray Gun - Must be selected to withstand pressure,
volume, temperature and chemicals in the system. Guns
must be durable to withstand the kind of abuse typical in
pressure wash applications. Consider comfort to reduce
operator fatigue. Ease if servicability is also important.
There are many types and styles of guns available. Be
sure to “shop around” and select one that most closely
fits your needs.
INSTALLING YOUR
COMPONENTS
Refer to manufacturer’s printed literature and install
all components according to manufacturer’s
recommendations to avoid serious bodily injury or
property damage and to insure proper system
operation.
All plumbing and component parts must be of the same
size or larger than is on the inlet and outlet of your pump.
The thread sizes are a guide to the required
sizes of plumbing for proper water flow both in and out
of the pump.
All plumbing and component parts must have an
operating pressure rating of at least 50% above the
maximum rated output pressure of the pump, and should
have an actual burst pressure of 3-5 times the normal
system working pressure.
HOSE FRICTION LOSS

Avoid bends and restrictions in the inlet and outlet
plumbing. They force the motor.engine to work harder to
drive the pump (reduction of efficiency) and create
turbulence in the water flow which can cause cavitation
on the inlet side and premature wear in the pump and in
the outlet plumbing. Bends and restrictions will cause a
reduction in outlet pressure and increased amp draws
with and electric motor.
Use a thread sealant on all plumbing connections and
tighten all connections securely to avoid air entering the
system. Avoid using hosed which are secured with
hose clamps, they are very susceptible to air leaks,
and will not retain very high pressures. Permanently
coupled hoses with appropriately sized pipe threads
installed are the best way to connect hose to hard
plumbing. Air leaks in the inlet plumbing will cause a re-
duction of outlet pressure, noisy pump operation, and
excessive wear and tear on the pump.
When mounting the pulleys on the pump and motor/
engine, install them as close as possible to the crankcase
(and crankcase bearing) to avoid an excessive side
load on the rotating parts. Be sure that the pulleys
are properly aligned to avoid excessive belt and pulley
wear and belt noise. Do not overtighten belts to avoid
an excessive side load on the rotating parts.
Mount the motor/engine in relationship to the pump
such that when running, the rotation of the pump
crankshaft is counterclockwise as you face the
pump crankcase or pulley. A gas engine has only
one rotation direction, which may vary between
manufacturers. Be sure you know the rotation direction
before you begin assembly. Most electric motors may be
operated in either rotation direction by changing the
wiring. Check the manufacturer’s specifications of your
motor to determine the proper rotation direction for your
application.
Water and electricity can be a very dangerous combina-
tion. Use extreme caution when installing or working on
electrical components. Always use watertight conduit,
connections, boxes, motors, switches, and other
electrical components. Never allow a water spray or leak
to come in contact with any electrical components to
avoid serious bodily injury or property damage. If you are
not sure about your electrical requirements, component
selection, or hook-up, seek the advice of a professional
electrician.
Always install a guard over belts and pulleys which meets
OS A standards to protect personnel from injury due to
contact with moving parts. Any moving part must be
covered to guard against serious bodily injury and
property damage.
Do not introduce acids or other caustic materials or any
abrasive into your pressure washer system or warranties
will be void and components in the system will be
damaged. Protect the pump and system from a freezing
condition.
8

9
PROBLEM CAUSE REMEDY
Pulsation Valve stuck open. Check all valves, remove foreign matter.
Faulty pulsation damper. Check precharge; if low, rechargeit or install a new one.
Low pressure
Worn nozzle. Replace nozzle, of proper size.
Belt slippage. Tighten or replace; use correct belt.
Air leak in inlet plumbing. Disassemble, reseal and reassemble.
Relief valve stuck; partially plugged or
improperly adjusted valve seat worn.
Clean, adjust relief valve; check for worn and dirty
valve seats. Kit available.
Inlet suction strainer clogged or improperly sized. Clean. Use adequate size. Check more frequently.
Worn packing. Abrasives in pumped fluid
or severe cavitation. Inadequate water.
I nstall proper filter. Suction at inlet manifold must be limited
to lifting less than 20 feet of water or -8.5 PSI vacuum.
Fouled or dirty inlet or discharge valves. Clean inlet and discharge valve assemblies.
Worn inlet, discharge valve blocked or dirty. Replace worn valve seats and/or discharge hose
Leaky discharge hose.
Pump runs extremely rough,
pressure very low.
Restricted inlet or air entering the inlet plumbing. Proper size inlet plumbing; check for air tight seal
Inlet restrictions and/or air leaks. Stuck
inlet or discharge valve.
Replace worn cup or cups, clean out foreign material,
replace worn valves.
Water leakage from under
manifold. Slight leakage.
Worn packing. Install new packing.
Cracked plunger. Replace plunger(s).
Oil leak between crankcase
and pumping section.
Worn crankcase piston rod seals. O-rings
on plunger retainer worn.
Replace crankcase piston rod seals. Replace
o-rings.
Oil leaking in the area of
crankshaft.
Worn crankshaft seal or inproperly
installed oil seal o-ring.
Remove oil seal retainer and replace damaged
o-ring and/or seals.
Bad bearing. Replace bearing and any spacer or cover damaged
by heat.
Excessive play in the end of
the crankshaft pulley.
Worn main bearing from excessive
tension on drive belt.
Replace crankcase bearing and/ or
tension drive belt.
Water in crankcase.
May be caused by humid air condensing i
nto water inside the crankcase
Change oil intervals. Use General Pump SAE 30
non-detergent oil.
Worn packing and/or piston rod sleeve,
o-rings on plunger retainer worn. Replace packing. Replace o-rings.
Cracked plunger Replace plunger(s).
Oil leaking from underside
of crankcase.
Worn crankcase piston rod seals. Replace seals.
Scored piston rod. Replace piston rod.
Oil leaking at the rear portion
of the crankcase.
Damaged crankcase, rear cover o-ring,
drain plug o-ring, or sight glass o-ring.
Replace cover or-ring, drain plug o-ring, or sight
glass o-ring.
Loud knocking noise in pump.
Pulley loose on crankshaft. Check key and tighten screw.
Broken or worn bearing on rod(s). Replace bearing or rod(s).
Valve stuck open or shut, or not opening enough. Replace bad valve.
Frequent or premature failure
of the packing.
Scored, damaged or worn plunger. Replace plungers.
Overpressure to inlet manifold. Reduce inlet pressure.
Abrasive material in the fluid being pumped. Install proper filtration on pump inlet plumbing.
Excessive pressure and/or temperature
of fluid being pumped.
Check pressures and fluid inlet temperature; be
sure they are within specified range.
Overpressure of pump. Reduce pressure.
Running pump dry. Do not run pump without water.
Upstream chemical injection. Use downstream chemical injection.
TROUBLESHOOTING

SERVICING YOUR
PUMP
VALVE ASSEMBLIES (Figure 1)
1. All inlet and discharge valves can be serviced
without disrupting the inlet or discharge
plumbing. The inlet and discharge valves
are identical in all models.
2. To service any valve, remove valve cap and
extract valve assembly.
3. Examine o-rings and replace if there is any
evidence of cuts abrasions or distortion.
4. Remove valve assembly (retainer, spring valve,
valve seat) from valve cavity.
5. Remove o-ring from valve cavity.
6. Only one valve kit is necessary to repair all the
valves in the pump. The kit included new o-rings,
valve seat, poppet, spring and retainer, all
pre-assembled.
7. Install new o-rings in valve cavity.
8. Insert assembly into valve cavity.
9. Replace valve cap and torque to specifications.
REMOVING MANIFOLD HEAD (Figure 2)
1. Remove the fasteners retaining the head.
2. Separate head from crankcase. NOTE: It may be
ecessary to tap head lightly with rawhide
mallet to loose . CAUTION: Whe slidi g head
from cra kcase use cautio ot to damage plu gers.
3. The V-packing assemblies may come off with
the head. At this point, examine plungers.
Plunger surfaces should be smooth and free
from scoring or pitting; if not, replace.
4. Reinstall manifold head and torque to
specifications per sequence described below.
TORQUE SEQUENCE FOR TIGHTENING HEAD
(Figure 4)
Install all head bolts fingertight. Torque to 10 foot pounds
in sequence as shown, then retorque to specifications,
again in sequence shown.
10
1
2
4

REPLACING PLUNGERS (Figure 3, 5 & 6)
1. Remove stainless steel piston screw and
plunger from piston rod.
2. If slinger washer comes off with plunger, be
certain this is replaced before new plunger is
installed.
3. Separate piston screw from plunger.
4. Install new o-ring and teflon backup ring on
piston screw. NOTE: A film of grease on the
outside of the o-rings insures a better
installation.
5. Carefully press piston screw into plunger.
6. Slide new plunger over the piston guide and
torque to specifications.
11
3
5
6

REPLACING V-PAC INGS (Figure 7, 8, 9 & 10))
1. Remove manifold from crankcase.
2. Insert proper extractor collet through main seal
retainer. Tighten collet and extract retainers,
v-packings and head rings.
3. Place proper insertion tool in cylinder and
install front head ring, v-packing and long life
ring and press firmly into cylinder until they
will go no further using proper insertion tool.
4. Insert intermediate seal retainer, pressing it
firmly into cylinder until it will go no further using
proper insertion tool. Install rear head ring,
v-packing and main seal retainer into cylinder
in order shown and press firmly into cylinder.
5. Repeat this sequence for each cylinder.
6. Coat each plunger with grease and carefully
remount manifold. Torque head to specifications.
General Pump
is a member of
the Interpump Group
GGEENNEERRAALL PPUUMMPP 1174 Northland Drive • Mendota eights, MN 55120
Phone: [phone] • Fax: [phone] • e-mail: [email protected] • www.generalpump.com
7
8
9
10
O-ring
Packing
Retainer
Low
Pressure
Seal
Intermediate
Ring
Restop
Ring
igh
Pressure
Seal
ead Ring
PAC ING ASSEMBLY