U.S. Jack D-51404, Instruction Manual

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FAILURE TO OPERATE
1. Release may not be completely closed.
2. Air-bound—see instruction No. 1.
3. Foreign matter in valve line—Repeat instruction
No.1
4. Too much oil—Lower to filler screw level.
5. Interior parts may be worn allowing oil to bypass.
Contact nearest Authorized Service Center.
MAINTENANCE AND LUBRICATION INSTRUCTIONS
1. Periodically check fluid level in power unit. Filler
plug is behind back cover which is removable with
four screws. Fluid level should be checked with lift
arm in lowest position and with unit on a level
surface. Fill to pipe plug level with recommended
hydraulic fluid.
2. Keep all moving parts clean and well lubricated.
Screw threads on tilt mechanisms require periodic
cleaning and lubricating if used in extremely dirty
areas.
3. Check all links and structural members for damage
or excessive wear.
TO REMOVE POWER UNIT—5-51903
1. Remove roll pin on bridge block at front of ram
2. Disconnect handle socket pin on top of pump piston
assembly.
3. Disconnect release knob by removing groove pin.
4. Remove “U” bolt at front of power unit.
5. Remove two (2) bolts holding base to frame.
SETTING THE RELIEF VALVE —See Figure 1
To set the relief valve, turn in the relief valve screw until
tight. Pump the power unit until the support plates are at
a height of 10 inches. Place a load of 2500 lbs. on the
support plates. Lift the load to see if the unit is function-
ing properly. While pumping, slowly turn out the relief
valve screw until the load cannot be lifted. The unit is
now set to lift a maximum of 2500 lbs. Place the
expansion plug in the relief valve hole to cover the screw
and prevent tampering.
After the unit has been rebuilt, an extended load test
should be run to determine if all parts have been
assembled and tightened correctly. The support plates
should be loaded with 2000 lbs. And the lift arm placed
at a height of 10 inches. The drop of the support plates
after a 30 minute period should not exceed .008 inches.
TROUBLE SHOOTING THE POWER UNIT
The following schematic drawings and reasons for
malfunction are a guide for solving power unit operation
problems.
SEE FIGURES 2 AND 3 on Page 4
A. POWER UNIT WILL NOT HOLD THE LOAD
When the power unit is under a load, the oil that is
supporting the load is trapped in the cavity bounded by the
ram, the release valve, and the discharge ball. If the oil is
escaping from that cavity, the jack will slowly retract.
Places from which oil can be escaping are:
1. The release valve, if it is not fully closed or if the seat is
damaged.
2. The ram packing, if it is worn out or damaged.
3. The discharge valve, if the seat is damaged or a for-
eign particles is holding the ball off its seat. If the suc-
tion valve is working, this normally results in a “handle
raiser”.
4. The valve block casting, if it is porous and incapable of
confining high pressure fluids.
5. The ram cylinder, if it is not turned in tight enough to
seal on the base.
6. The release insert, if it is not turned in tight enough to
seal in the base.
7. The relief valve, if it is not properly set or if the seat is
damaged.
B. RAM WILL NOT MOVE WHEN HANDLE IS PUMP.
This could be due to one of the following:
1. There is no oil in the reservoir or oil is low in the
reservoir. The oil level should be up to the filler plug
hole.
2. The intake valve is not functioning. The ball is either
jammed into the seat and will not dislodge or the ball is
being held off the seat by foreign materials and the oil
merely swishes back and forth.
3. Power unit is air bound. Every jack has air in the
reservoir, along with the oil. As long as the air stays at
that location, it does not cause any trouble. However, if
air finds its way to any other part of the system, the jack
might become air bound.
When a large air bubble forms between the intake and
pressure ball, the jack usually becomes inoperable. As the
pump moves up and down trying to pump oil, the bubble
just expands and contracts, preventing the formation of a
vacuum in the pump chamber and halting the flow of oil
from the reservoir.
A large bubble under the ram is not nearly as damaging,
but it gives the ram an annoying “bouncy” action.
To bleed the system of air, make sure the unit is on a level
service. With no load on the unit, pump to full height and
open the relief valve wide to lower the unit. Remove the
reservoir plug to allow any excess air to escape. Repeat
this several times and all air should be removed from the
pumping chamber.
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