Yale MPB040-E User manual

Maintenance
WALKIE HYDRAULIC
SYSTEMS
MPB040E [B827];
MPW045-E [B802];
MPW050-E [C802]
PART NO. 524154894 1900 YRM 1018

SAFETY PRECAUTIONS
MAINTENANCE AND REPAIR
•When lifting parts or assemblies, make sure all slings, chains, or cables are correctly fas-
tened, and that the load being lifted is balanced. Make sure the crane, cables, and chains
have the capacity to support the weight of the load.
•Do not lift heavy parts by hand, use a lifting mechanism.
•Wear safety glasses.
•DISCONNECT THE BATTERY CONNECTOR before doing any maintenance or repair on
electric lift trucks. Disconnect the battery ground cable on internal combustion lift trucks.
•Always use correct blocks to prevent the unit from rolling or falling. See HOW TO PUT THE
LIFT TRUCK ON BLOCKS in the Operating Manual or the Periodic Maintenance section.
•Keep the unit clean and the working area clean and orderly.
•Use the correct tools for the job.
•Keep the tools clean and in good condition.
•Always use YALE APPROVED parts when making repairs. Replacement parts must meet
or exceed the specifications of the original equipment manufacturer.
•Make sure all nuts, bolts, snap rings, and other fastening devices are removed before using
forcetoremoveparts.
•Always fasten a DO NOT OPERATE tag to the controls of the unit when making repairs, or
if the unit needs repairs.
•Be sure to follow the WARNING and CAUTION notes in the instructions.
•Gasoline, Liquid Petroleum Gas (LPG), Compressed Natural Gas (CNG), and Diesel fuel are
flammable. Be sure to follow the necessary safety precautions when handling these fuels
and when working on these fuel systems.
•Batteries generate flammable gas when they are being charged. Keep fire and sparks away
from the area. Make sure the area is well ventilated.
NOTE: The following symbols and words indicate safety information in this manual:
WARNING
Indicates a condition that can cause immediate death or injury!
CAUTION
Indicates a condition that can cause property damage!

Walkie Hydraulic Systems Table of Contents
TABLE OF CONTENTS
General................................................................................................................................................................ 1
Operation............................................................................................................................................................. 1
Lifting a Load................................................................................................................................................... 1
Lowering a Load.............................................................................................................................................. 1
Hydraulic Lines................................................................................................................................................ 1
Hydraulic Oil.................................................................................................................................................... 2
Cleanliness...................................................................................................................................................... 2
Sound Level .................................................................................................................................................... 3
Hydraulic Unit ...................................................................................................................................................... 4
Remove........................................................................................................................................................... 4
Special Precautions ........................................................................................................................................ 4
Install............................................................................................................................................................... 4
Hydraulic Pump ................................................................................................................................................... 5
Remove........................................................................................................................................................... 5
Install............................................................................................................................................................... 5
Hydraulic Pump Reservoir................................................................................................................................... 7
Remove........................................................................................................................................................... 7
Install............................................................................................................................................................... 7
Hydraulic Cylinder ............................................................................................................................................... 8
Remove........................................................................................................................................................... 8
Repacking ....................................................................................................................................................... 9
Install............................................................................................................................................................... 9
Relief Valve Adjustment....................................................................................................................................... 10
Relief Valve Pressure Check........................................................................................................................... 10
Relief Valve Adjust .......................................................................................................................................... 11
Troubleshooting ................................................................................................................................................... 12
Lift Assemblies ................................................................................................................................................ 12
Hydraulic Cylinders ......................................................................................................................................... 12
Hydraulic Pump............................................................................................................................................... 13
This section is for the following models:
MPB040E [B827];
MPW045-E [B802];
MPW050-E [C802]
©2007 Yale Materials Handling Corp. i

1900 YRM 1018 Operation
General
The hydraulic system provides the force required to lift
the loads on all motorized lift trucks.
The hydraulic system on the motorized lift truck consists
of the following individual components:
•Pump Motor Assembly
•Hydraulic Pump Assembly
•Solenoid Lowering Valve
•Pilot Relief Valve
•Lift Cylinder
•Reservoir
The hydraulic pump and motor assemblies are mechan-
ically joined together as a compact unit, combining the
reservoir, pump, and motor together as a single assem-
bly. The pump is located inside of the hydraulic tank and
coupled to the motor by an adapter plate, coupler drive,
and four capscrews.
Hydraulic unit servicing is best performed by removing
the unit from the truck to a clean work area.
Operation
LIFTING A LOAD
To raise a load, the lift button must be depressed. De-
pressing this switch will activate the pump motor. This
torque is transferred to the pump from the motor through
the motor shaft and shaft coupling.
Hydraulic oil is pumped through the system as the
pump begins to operate. A vacuum created inside of
the pump draws oil out of the reservoir through the suc-
tion line. Air which is drawn into the reservoir through
the breather displaces the pumped oil, allowing it to
be sent through the system. See Figure 1, Figure 2,
and Figure 3. If the breather is clogged or blocked the
ability of the system to lift a load will be greatly reduced.
Figure 1. Hydraulic Schematic
As oil is pushed out of the pump, it passes through a
one-way check valve to the lift cylinder. The check valve
prevents oil from flowing back to the pump when lifting
ceases, holding the lift cylinder in the raised position
until lowered.
The piston will begin to lift the load when fluid pressure
acting against it is high enough to overcome the weight
of the load at rest on the forks/platform.
When the piston is fully extended to the end of its stroke
or if the load is too heavy, pressure will continue to
build until the rated pressure needed to operate the
relief valve is reached. When this occurs, the relief
valve, which is normally closed, is forced back against
its spring, creating a path for the fluid to flow back to the
reservoir.
Once relief valve pressure is reached, hydraulic oil will
continue to be diverted from the lift cylinder to the reser-
voir until the lift button is released or electrical power is
interrupted.
LOWERING A LOAD
A load is lowered by depressing the lower button. When
the lower button is depressed, electric current is sent
to the normally closed solenoid lowering valve, which
causes it to change position and open a path for the
trapped hydraulic oil to flow from the cylinder back to
the reservoir.
HYDRAULIC LINES
1. All hydraulic lines must be thoroughly cleaned be-
fore installation.
1

Operation 1900 YRM 1018
2. When making repairs, use the least number of fit-
tings and connections to minimize flow resistance
and the possibility of leakage.
HYDRAULIC OIL
The hydraulic oil in the system performs the dual func-
tion of the power transmission and lubrication. Using
the correct fluid is essential to proper system operation.
Refer to the Lubrication Charts for the recommended
hydraulic oil to be used.
Check the reservoir level when troubleshooting lifting
problems. Low oil levels will make it appear that a prob-
lem exists with the battery or hydraulic system.
CLEANLINESS
Adhere to the following precautionary steps to ensure
that the hydraulic system remains clean.
1. Flush the entire system when a failure is encoun-
tered to make sure all paint, metal chips, welding
shot, and debris are removed.
2. Filter each change of oil to prevent the introduction
of contaminants into the system.
3. Provide continuous protection from airborne con-
tamination by keeping the breather clean and ser-
viceable.
1. HYDRAULIC POWER UNIT
2. CAPSCREW
3. WASHER
4. LOCKWASHER
5. CAPSCREW
6. FITTING
7. HOSE
8. TUBE
9. FITTING
10. ADAPTER
11. FITTING
12. LIFT CYLINDER
13. SPACER PLATE
Figure 2. Hydraulic System - 12 Volt
2

1900 YRM 1018 Operation
SOUND LEVEL
Hydraulic system noise is caused by both improperly
selected oil and loose or damaged system components.
•Hydraulic oil with high or moderately high viscosities -
At startup, temperatures can cause pump noises due
to cavitation and also impedes the release of trapped
air. Air does not have sufficient time to purge itself
from the fluid while in the reservoir before recycling
through the system.
•Aerated Hydraulic Oil - Results in system noise that is
similar to cavitation. Aerated oil is caused by the in-
gestion of air through the pipe joints of the inlet lines
and high velocity discharge lines, as well as cylinder
rod packing. Aeration can also be caused by oil dis-
charging above the fluid level.
1. HYDRAULIC POWER UNIT
2. CAPSCREW
3. WASHER
4. LOCKWASHER
5. CAPSCREW
6. FITTING
7. HOSE
8. TUBE
9. FITTING
10. ADAPTER
11. FITTING
12. LIFT CYLINDER
Figure 3. Hydraulic System - 24 Volt
3

Hydraulic Unit 1900 YRM 1018
Hydraulic Unit
REMOVE
WARNING
Batteries are heavy and can cause personal injury.
Usecaretoav
oid injury. DO NOT put hands, arms,
feet, and/or legs between the battery and a solid
object. Make sure the capacity of the crane and
spreader bar is greater than the weight of the bat-
tery. The weight of the battery is normally shown
on the battery case. The maximum battery weight
is shown on the lift truck nameplate. The spreader
bar must NOT be made of metal or it must have in-
sulated straps.
WARNING
Put blocks under each side of the truck under the
drive unit frame. Position blocks on both sides of
the load wheels. The blocks must prevent the lift
truck from falling and causing personal injury or
property damage.
WARNING
The capacitor in the transistor controller can hold
an electrical charge after the battery is discon-
nected. To prevent electrical shock and personal
injury, discharge the capacitor before inspecting
or repairing any component in the drive unit com-
partment. Wear safety glasses. Make certain the
battery has been disconnected. Refer to the sec-
tion Steering Mechanism 1600 YRM 1004.
CAUTION
Make certain the hydraulic cylinder is fully col-
lapsed.
1. Remove the drive unit compartment cover.
2. Disconnect the battery. Use a spreader bar and
lifting device to remove the battery. DO NOT allow
the battery move from side to side. Make sure the
battery cables have clearance.
3. Raise the drive wheel off the floor and put blocks
under both sides of the drive unit frame.
4. Drain the hydraulic oil from the hydraulic unit into
an appropriate container.
5. Tag and disconnect all of the electrical wires from
the hydraulic unit.
6. Remove the hydraulic lines from the hydraulic unit.
7. Loosen and remove the three capscrews attaching
the hydraulic unit to the frame. Remove the hy-
draulic unit and place in a clean work area.
SPECIAL PRECAUTIONS
WARNING
To avoid personal injury and prevent electrical
shock, perform the following steps before perform-
ing any troubleshooting and/or adjustments, and
connecting or disconnecting a handset or PC.
CAUTION
To avoid controller damage always disconnect the
battery. Discharge the capacitor, and never put
power to the controller with any power wire dis-
connected. Never short any controller terminal or
motor terminal to battery. Make sure to use proper
procedure when servicing the controller. Refer to
the section Steering Mechanism 1600 YRM 1004.
1. Block the lift truck so that the drive wheels are off
the floor. See the section Periodic Maintenance
8000 YRM 1009, How to Put a Lift Truck on Blocks.
2. Turn the key switch to the OFF position and unplug
the battery.
3. After key-off, the capacitors in the unit remain
charged for several minutes. To discharge the
capacitors, connect a 200-ohm, 2-3W resistor be-
tween +BATT and BATT on the controller. Hold
for 5 seconds.
4. Tag and disconnect all electrical wires to the hy-
draulic unit.
5. Disassemble and plug the hydraulic lines to the hy-
draulic unit.
INSTALL
1. Align the hydraulic unit with the mounting holes in
the frame and install the three capscrews. Tighten
the hydraulic unit mounting capscrews to 49 N•m
(36 lbf ft).
2. Install the hydraulic lines to the hydraulic unit.
3. Connect all the electrical wires to the hydraulic unit.
4

1900 YRM 1018 Hydraulic Pump
4. Remove the blocks and lower the lift truck to the
floor.
5. Remove the breather and add the recommended
hydraulic oil until the oil level reaches the full level
mark. Replace the breather. If too much hydraulic
oil is added, the oil will leak from the breather during
operation.
6. Install the battery and connect the battery. Operate
the lift truck until the hydraulic oil reaches operating
temperature. Add additional oil if necessary. Check
for hydraulic oil leaks.
7. Install the drive unit compartment cover. Test the
operation of the lift truck prior to returning the truck
to service.
Hydraulic Pump
REMOVE
1. Remove the hydraulic unit from the lift truck. Refer
to the Hydraulic Unit in this section.
2. Cleanthereservoirandpumpareatopreventcon-
taminants from entering the hydraulic system.
3. Remove the capscrews retaining the reservoir to
the hydraulic unit. Tap around the perimeter to
break the seal and separate the reservoir from the
motor assembly.
4. Remove the spring retaining screw from the suction
tube.
5. Remove the suction tube and strainer by pulling
down and out.
6. Remove the four capscrews retaining the pump to
the drive motor.
7. Disassemble the pump assembly and coupling from
the adapter.
INSTALL
NOTE: The hydraulic unit includes four separate kits as
showninFigure4.
1. Clean and lubricate all components using clean hy-
draulic oil.
2. Replace all O-rings and seals within the unit.
3. Grease the coupler and coupler cavity with the mo-
tor resting with the adapter plate up. Align the pump
mounting holes with the holes in the motor. Ensure
that the tank is seated into the motor.
4. Install the four capscrews and tighten to 13.6 to
16.3 N•m (10 to 12 lbf ft).
5. Install the O-rings into the pump cavities. Apply
grease to the return tubes. Insert tubes into pump
cavities and O-rings. Grease the suction tube and
insert into locking device with hole. Install and
tighten the spring retaining screw to secure the
suction tube.
6. Remove the retainer and replace the O-ring. Lightly
grease the O-ring before installation.
7. Align the reservoir so the hose connections will be
in the same position as they were prior to removal.
Install the four capscrews to retain the reservoir.
8. Install the hydraulic unit. Refer to Hydraulic Unit,
Install in this manual.
9. Remove the breather and fill the reservoir with the
recommended oil. See the section Capacities and
Specifications 8000 YRM 1010. Add oil until the
oil is up to the full mark. If too much oil is added,
the oil will leak from the breather during operation.
If too much oil has been added, drain the excess or
useasuctiondevicetoremovesomeoftheoil.
10. Run the pump for 5 seconds and energize the low-
ering valve at the same time so that oil gets through
the pump body and valve at 0.0 psi. Operate the
forks up and down three or four times to remove air
from the system. Operate the lift truck until the hy-
draulic oil reaches operating temperature. Remove
the breather and check the hydraulic oil level. Add
additional oil if necessary. Check for hydraulic oil
leaks.
11. Install the drive unit compartment cover. Test the
operation of the motorized hand truck before return-
ing the truck to service.
5

Hydraulic Pump 1900 YRM 1018
Figure 4. Hydraulic Unit
6

1900 YRM 1018 Hydraulic Pump Reservoir
Legend for Figure 4
1. MOTOR
2. ELECTRO-POPPET VALVE 3. HYDRAULIC SUB UNIT 4. FILLER TANK
Hydraulic Pump Reservoir
REMOVE
The reservoir of the hydraulic pump unit can be re-
moved without removing the complete hydraulic unit.
The motor will also come loose, with one set of screws
holding the reservoir to the subunit to the motor.
WARNING
The capacitor in the transistor controller can hold
an electrical charge after the battery is discon-
nected. To prevent electrical shock and personal
injury, discharge the capacitor before inspecting
or repairing any component in the drive unit com-
partment. Wear safety glasses. Make certain the
battery has been disconnected. Refer to the sec-
tion Steering Mechanism 1600 YRM 1004.
CAUTION
Make certain the hydraulic cylinder is fully col-
lapsed.
NOTE: The reservoir must be lowered below the suc-
tion tube before attempting to move the reservoir away
from the lift truck. Remember the reservoir may contain
hydraulic oil. Dispose of all used oil in accordance with
local regulations.
1. Move the key to the OFF position. Disconnect the
battery.
2. Remove the drive unit compartment cover.
3. Discharge the capacitor in the transistor controller.
4. Disassemble and plug the hydraulic lines to the hy-
draulic unit.
5. Remove the four capscrews retaining the reservoir
to the hydraulic unit. Carefully remove the reservoir.
6. Clean the reservoir and the suction screen. Inspect
the screen for damage and replace if necessary.
NOTE: On 24-volt trucks, the capscrews that hold the
reservoir to the subunit also hold the motor to the sub-
unit. When the capscrews are removed, the motor will
be resting on the subunit. When reinserting the cap-
screws, ensure that the motor is located correctly and
the coupler is seated properly.
INSTALL
1. Lubricate a new O-ring using clean hydraulic oil and
install into the pump body.
2. Align the reservoir in the proper position and install
the four capscrews to retain the reservoir to the hy-
draulic unit.
3. Install the hydraulic lines to the hydraulic unit.
4. Remove the blocks and lower the lift truck to the
floor.
5. Remove the breather and add the recommended
hydraulic oil until it reaches the full mark. Replace
the breather. If too much hydraulic oil is added, the
oil will leak from the breather during operation. If
too much oil has been added, drain or use a suction
device to remove excess oil.
6. Connect the battery. Run the pump for 5 seconds
and energize the lowering valve at the same time
so that oil gets through the pump body and valve
at 0.0 psi. Operate the forks up and down three or
four times to remove air from the system. Operate
the lift truck until the hydraulic oil reaches operating
temperature. Remove the breather and check the
hydraulic oil level. Add additional oil if necessary.
Check for hydraulic oil leaks.
7. Install the drive unit compartment cover. Test the
operation of the lift truck prior to returning the truck
to service.
7

Hydraulic Cylinder 1900 YRM 1018
Hydraulic Cylinder
REMOVE
WARNING
Put blocks under each fork. Position blocks on both
sides of the drive wheel. The blocks must prevent
the lift truck from falling and causing personal in-
jury or damage.
WARNING
Be careful when removing or installing snap rings.
The snap rings can come loose during removal or
installation with enough force to cause a personal
injury. Always use the correct snap ring pliers, and
wear eye and face protection during removal and
installation.
1. Raise the motorized lift truck forks/platform to one
half its maximum height.
2. Place blocks under the forks. Block the drive wheel.
See the section Periodic Maintenance 8000 YRM
1009, How to Put a Lift Truck on Blocks.
3. Remove the drive unit compartment cover.
4. Separate the frames. Refer to the section Frame
100 YRM 1015.
5. Manually collapse the piston into the cylinder while
depressing the lower switch.
6. Relieve pressure from the hydraulic cylinder. See
Figure 5.
1. ROD
2. SEAL
3. RING
4. SEAL
5. SEAL
6. GLAND
7. SEAL
8. BARREL
9. PISTON
10. SEAL
11. NUT
12. BEARING
13. RING
Figure 5. Hydraulic Cylinder
8

1900 YRM 1018 Hydraulic Cylinder
7. Drive the roll pin retaining the top clevis pin out of
the frame and clevis pin. Remove the top clevis pin.
8. Remove the roll pin retaining the bottom clevis pin.
Remove the bottom clevis pin and the hydraulic
cylinder.
REPACKING
CAUTION
Lubricate the seals, packing, and O-rings with clean
hydraulic oil before assembling. Make certain to
install spacers, if any were removed.
CAUTION
Make certain that none of the sealant gets into the
cylinder. Allowing sealant to get into the hydraulic
system may cause damage to the components
within the hydraulic system.
1. Move the cylinder toward the rear of the truck.
Loosen the gland nut. Extract the piston, gland
nut, and rod from the cylinder.
2. Disassemble the nut and piston from the cylinder
rod. Remove the spacers, if used, and slide the rod
out of the gland nut.
3. Replace all seals, packing, and O-rings.
4. Install the seals, packing, and O-rings as necessary
into the gland and piston after coating them with
clean hydraulic oil.
5. Carefully install the rod through the gland nut. In-
stall the piston, spacer (if necessary), and the lock
nut. Tighten the lock nut (lubricated) to 150 N•m
(110 lbf ft).
6. Carefully install the rod assembly into the cylinder.
Apply Loctite®242 or equivalent to the threads of
the gland nut. Tighten the gland nut to 27 N•m
(20 lbf ft).
INSTALL
WARNING
Be careful when removing or installing snap rings.
The snap rings can come loose during removal or
installation with enough force to cause a personal
injury. Always use the correct snap ring pliers and
wear eye and face protection during removal and
installation.
1. Align the bottom of the cylinder with the frame and
install the bottom clevis pin.
2. Install the roll pin to retain the clevis pin.
3. Alignthetopofthecylinderrodwiththeframeand
install the top clevis pin. Install the roll pin to retain
the clevis pin.
4. Assemble the frames. Refer to the section Frame
100 YRM 1015.
5. Remove the blocks and lower the lift truck to the
floor.
6. Remove the breather and add the recommended
hydraulic oil until the oil is up to the full mark.
Replace the breather. If too much hydraulic oil is
added, the oil will leak from the breather during
operation. If too much oil has been added, drain
the excess or use a suction device to remove some
of the oil.
7. Run the pump for 5 seconds and energize the low-
ering valve at the same time so that oil gets through
the pump body and valve at 0.0 psi. Operate the
forks up and down three or four times to remove air
from the system. Operate the lift truck until the hy-
draulic oil reaches operating temperature. Check
the hydraulic oil level. If necessary add additional
oil. Check for hydraulic oil leaks.
8. Install the drive unit compartment cover. Test the
operation of the lift truck prior to returning the truck
to service.
9

Relief Valve Adjustment 1900 YRM 1018
Relief Valve Adjustment
RELIEF VALVE PRESSURE CHECK
WARNING
DO NOT make repairs or adjustments unless you
have been properly trained and authorized to do so.
Improper repairs and adjustments can create dan-
gerous operating conditions. DO NOT operate a lift
truck that needs repair. Report the problem to your
supervisor immediately. If repairs are necessary,
turn the key switch to the OFF position, attach a DO
NOT OPERATE tag to the control handle, and dis-
connect the battery.
Always wear the proper protective equipment in-
cluding eye protection and petroleum resistant
gloves when servicing hydraulic components.
Thoroughly wash oil from exposed areas of skin as
soon as possible.
Completely lower all lift components and relieve
pressure before disassembling any part of the lift
pump or disconnecting any hydraulic hoses.
The hydraulic oil is hot at normal operating temper-
atures. Be careful when draining the oil.
Never put your hands on pressurized hydraulic
components. Pressurized hydraulic oil escaping
through pin-hole leaks can be injected into the
skin.
CAUTION
DO NOT OVERFILL. Oil will leak from the breather/
filler cap if too full.
NOTE: Check the hydraulic oil level in the reservoir
when oil is at room temperature. Remove breather cap
and add recommended hydraulic oil to proper level, as
required. See Hydraulic Pump Reservoir.
1. Operate lift truck until hydraulic oil reaches operat-
ing temperature (43 to 49 C (110 to 120 F)).
2. Lower the forks completely to relieve pressure from
hydraulic circuit.
3. Tur n key to the OFF position and disconnect the
battery.
4. Block load wheels to prevent lift truck from moving.
5. Remove the drive unit compartment covers.
6. Discharge the capacitor. See Special Precautions.
7. Clean any buildup of dirt from around the lift pump
and motor assembly.
WARNING
Hydraulic oil hoses and lines may be under pres-
sure. Slowly loosen the hydraulic connections to
ensure pressure has been relieved.
8. Disconnect the hydraulic hose at the pump.
9. Install a tee fitting and a pressure gauge of at least
24.8 MPa (3600 psi).
10. Verify the oil is at an operating temperature of 43 to
49 C (110 to 120 F).
11. Raise the forks completely and continue to hold the
lift button. Read the pressure gauge while the pump
is in relief. See Relief Valve Settings for correct
pressures.
Table 1. Relief Valve Settings
Model Relief Setting*
4000 lb 16.9 MPa (2450 psi)
4500 lb
12 Volt
19.3 MPa (2800 psi)
4500 lb
24 Volt
18.6 MPa (2700 psi)
5000 lb 22.0 MPa (3200 psi)
*+0.6 0.0 MPa (+87 0psi)@21C(70F)
Oil Temperature Full Flow
NOTE: Thepumpwillstopafterashortperiodoftime.
Releasethelowerbuttonthenpressandholdagainto
continue.
12. If the relief pressure is incorrect, refer to Relief
Valve Adjust.
13. After the proper relief pressure is obtained, lower
the forks completely to relieve pressure from hy-
draulic circuit.
10

1900 YRM 1018 Relief Valve Adjustment
14. Tur n key switch t o OFF position. Disconnect the
battery.
15. Discharge the capacitor. See Special Precautions.
16. Remove the pressure gauge and tee.
17. Reconnect the hydraulic hose to pump.
18. Connect the battery and turn the key switch to ON
position.
19. Operate the hydraulic functions several times to
purge the air from the hydraulic circuit.
20. Remove blocks from wheels.
21. Test the lift truck by lifting and lowering a load sev-
eral times. Visually check for leaks.
CAUTION
DO NOT OVERFILL RESERVOIR. Oil will leak from
the breather/filler cap during operation if reservoir
is over filled.
22. Check the hydraulic oil level in the reservoir.
Remove breather cap and add recommended
hydraulic oil to proper level, as required. See
Hydraulic Pump Reservoir.
23. Install the drive unit compartment covers.
RELIEF VALVE ADJUST
Refer to Relief Valve Pressure Check to determine if
adjustment is necessary.
1. Verify the key switch is in the OFF position and the
battery is disconnected.
2. Remove the hydraulic reservoir. See Hydraulic
Pump Reservoir.
3. Loosen the locking nut on the relief valve. See Fig-
ure 6.
4. Adjust the relief valve screw in small increments.
Turn the adjustment screw clockwise to increase
pressure. Turn the adjustment screw counterclock-
wise to decrease pressure.
5. Tighten the lock nut and torque to 15 N•m (11 lbf ft).
6. Install the hydraulic reservoir as removed.
Connect the battery and turn key to ON position.
7. Recheck the relief pressure. See Relief Valve Pres-
sure Check.
8. Repeat as necessary, until the correct relief pres-
sure is measured.
9. Perform Step 13 through Step 23 in Relief Valve
Pressure Check to complete procedure.
1. LIFT MOTOR
2. PUMP HOUSING
3. TUBE
4. CLAMP
5. INLET ADAPTER
6. SCREEN
7. SNAP RING
8. ADJUSTMENT SCREW
9. LOCK NUT
10. RELIEF VALVE ASSEMBLY
Figure 6. Relief Valve Adjust
11

Troubleshooting 1900 YRM 1018
Troubleshooting
LIFT ASSEMBLIES
PROBLEM POSSIBLE CAUSE PROCEDURE OR ACTION
Forks fail to elevate. Faulty hydraulic equipment. See Pumps and Hydraulic Cylinders
below.
Deformed lifting components. Disassemble and replace damaged
parts.
Slow lifting speed and insuffi-
cient handling capacity.
Faulty hydraulic equipment. See Pumps and Hydraulic Cylinders
below.
Deformed lifting components. Disassemble and replace damaged
parts.
Forks failtolower. Deformed forks. Disassemble, repair, or replace.
Deformed lifting components. Disassemble, repair, or replace.
Bent hydraulic cylinder piston rod. See Hydraulic Cylinders below.
HYDRAULIC CYLINDERS
PROBLEM POSSIBLE CAUSE PROCEDURE OR ACTION
Oil leaks from cylinder gland
around piston rod (An oil ring
appears on the piston rod).
Foreign matter on packing. Replace packing.
Score on piston rod. Remove any foreign matter. Smooth
rod surface with an oil stone. If oil still
leaks, disassemble and repack cylin-
der.
Scores on wiper ring lip. Replace wiper ring.
Unusual distortion of wiper ring. Replace wiper ring.
Chrome plating is stripped. Replace piston rod or renew chrome
plating.
Oil leaks from welded portion. Cylinder tube damaged. Replace cylinder tube.
12

1900 YRM 1018 Troubleshooting
PROBLEM POSSIBLE CAUSE PROCEDURE OR ACTION
Rod spontaneously retracts. Scores on inner surface of tube. Smooth surface with an oil stone.
Score on tube. Replace cylinder tube.
Scoreonpisto
nring. Replace pistonring.
Foreign matter on packing ring. Replace packing.
Considerablescoreonlipofpacking
ring.
Replace packing.
Unusual distortion of packing ring. Replace packing.
Wear limit (clearance between
cylinder tube and wear ring).
Excessive clearance between cylinder
tube and wear ring.
Replace wear ring (included in packing
kit).
HYDRAULIC PUMP
PROBLEM POSSIBLE CAUSE PROCEDURE OR ACTION
Pump not delivering oil. Pump does not draw oil. Check pump, piping, and valves for
leaks.
Low oil level in reservoir. Check fluid level.
Clogged screen at pump inlet. Change oil and clean screen.
Pump pressure fails to rise. Improperly adjusted relief valve. Increase to specified pressure using a
pressure gauge.
Relief valve clogged. Disassemble and clean with fresh oil.
Interfering relief valve or broken relief
spring.
Disassemble valve and replace spring.
Air suction. Check piping on suction side for leaks.
Add oil to reservoir.
Check pump seals.
13

Troubleshooting 1900 YRM 1018
PROBLEM POSSIBLE CAUSE PROCEDURE OR ACTION
Pump produces noise. Cavitation caused by collapsed suc-
tion hose or clogged screen.
Drain and clean system.
Faulty oil suction. Add oil to specified level.
Air suction through loose connections
on suction side.
Tighten all hose connections on suc-
tion side.
Air suction from pump oil seal. Disassemble pump and replace oil
seals.
Breather clogged. Clean or replace breather.
Cavitation caused by high oil viscosity. Change to recommended oil and op-
erate pump in recommended temper-
ature ranges.
Abnormal temperature rise of
hydraulic oil.
Overwork. Adjust workload to fall within pump’s
operating range.
Improper viscosity or contaminated oil. Drain and replace oil with recom-
mended oil.
Pump case or drive gear bro-
ken.
Incorrect pressure setting. Check for excessive resistance in hy-
draulic circuit. Make certain relief pres-
sure is properly adjusted and valve is
working properly.
14

Yale Materials Handling Corp.
1400 Sullivan Dr., Greenville, NC 27834-2011
1900 YRM 1018 4/07 (8/05)(9/03)(1/02) Printed in U.S.A.