2. Charge pressure relief valve in the motor manifold stuck
open. Pressure will be normal when the pump is in neutral
but low in stroke.
3. Internal damage to pump or motor.
G. Faulty Check Valves.
1. Remove the two ball check valves located in the end cap of
the pump under the charge pump and check the following:
a. Check valve to see if poppet or ball is missing.
b. Check to see if the valve seat is eroded.
NOTE: If any of the above conditions exist, replace both
check valves.
H. Internal Damage to Pump or Motor.
Indicated by:
1. Low or zero charge pressure (see I-E). Charge pressure may
also fluctuate rapidly.
2. Maximum obtainable operating pressure in both forward and
reverse is less than the normal relief valve setting. Charge
pressure, which will also be lower than normal, will drop to
zero when the maximum pressure is reached.
3. Pieces or flakes of brass in the reservoir and filter.
4. Noisy unit (pump or motor). If either unit is considerably
worn or damaged, the other unit should also be carefully
checked.
I.
Plugged Control Orifice
1. Remove displacement control valve from pump and inspect
orifice and "0" rings.
II. System Operates in One Direction Only.
Cause
Remedy
A. Faulty Control Linkage.
1. Check the entire linkage to make sure it is connected and
free to operate as it should.
2. Make sure the control "stop," if used, is not out of adjustment.
B. High Pressure Relief Valve Stuck Open.
1. Switch the two high pressure relief valves. If the system
operates in the direction in which it would not operate before,
one of the high pressure relief valves is stuck open. Both
relief valves should be examined and the stuck relief valve
disassembled, cleaned, and then reassembled and both relief
valves should then be reinstalled in the system.
C. One Check Valve Faulty.
Follow instructions given in I-G.
D. Faulty Directional Control Valve.
NOTE: Do not change the position of any of the hex nuts or
(Located on Pump).
the slotted plug on the end of the control unless it is
necessary to remove the control valve spool.
1. Disconnect control linkage at directional control arm. Move
the control arm back and forth by hand. If it moves freely
with no resistance, even as little as 150, the control valve
should be removed and checked for broken parts or a bent
control shaft to which the control arm is attached.
E. Displacement Control Valve"0" Ring Leaking
1. Remove displacement control valve from pump and inspect
"0" rings.
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