LOSS OF PRESSURE FROM PRESS CYLINDER

TM 94940-539-14&P

2. The only other reason for failure of the high-pressure pump to develop pressure is oil escaping around the inlet check

while on the compression stroke, 'caused by dirt or a faulty valve seat. Also, but most improbable, is the possibility of

leakage of the relief valve.

3. In the low pressure circuit the two possible reasons for leakage of fluid to the reservoir (not developing pressure)

during the compression stroke are leakage of the inlet check valve located above the large plunger, or fluid escaping

at the high volume pump control valve (right side of pump unit).

If any of the above mentioned check valves leak, it is best to order a rebuilt pump unit as described above. If you

wish to repair it yourself, remove by using a 5/16 hexagon wrench. After examination of same, clean, reseat, or

replace as indicated. If the valve seat is to be reseated, squeeze the ball and valve seat together in a vise, using only

enough force to perfect the seat, avoid making a wide seat. A narrow valve seat is essential. Re-machine or replase

if necessary.

4. If the pump handle rebounds, that is, if the pump handle lifts up, this indicates a faulty outlet check valve of one of the

pumps (fluid under pressure leaking from the cylinder circuit back through the outlet check valve into the pump area,

resulting in moving the plunger out). If this occurs while using only the high pressure pump (small plunger), then

obviously the high pressure pump is at fault.

5. If rebounding occurs while using both pumps but stops rebounding when the high speed pump (large plunger) is

turned to the SPEED SLOW position, this proves the high speed pump check valve is leaking. This condition allows

fluid to leak from the cylinder circuit, resulting in a pressure drop which is indicated by the pressure gauge.

The pump outlet check valves are located above the pumps under the solid 3/% pipe plugs as shown in the

schematic hydraulic circuit drawing.

P. LOSS OF PRESSURE FROM PRESS CYLINDER

There are four ways that fluid can escape from the cylinder: by a leaking ram cup, through the ram limit valve, by way

of the pump outlet check valves, and at the cylinder release valve located in the pump unit.

If a leak exists at the ram cup or through the ram limit valve, fluid will come out of the fitting in the lower end of the

cylinder which connects to the top of the pump reservoir. Dis- connect the drain hose at the cylinder and maintain

pressure on the cylinder (continue to pump if necessary) to see if fluid continues to come out of the drain line fitting on the

side of the cylinder. If so, one of the two above mentioned conditions exist. Remember that fluid will escape if the ram is

at the end of its normal travel.

Sometimes, if dirt is causing the limit valve to leak, it can be washed away by pumping the cylinder ram all the way out

with the fast pumping speed and continuing to pump after the limit valve opens. Allow ram to retract and test. If

necessary, remove ram from cylinder to inspect leather cup and limit valve. The limit valve must have from .010 to .015

clearance between the ball and its push rod. Before reassembly clean thoroughly.

If it is determined that the cylinder ram cup and ram travel limit valve do not leak, and the pump handle does not

rebound, then the cylinder control valve located in the pump is at fault. If it is at fault, purchase an exchange rebuilt pump

from our factory as described above.