MDP Operation & Maintenance Manual | 29
TROUBLESHOOTING
FIRST STEPS
• Ensure the hydraulic ow and pressure from the base machine meets specications (see “Hydraulic Circuit
Requirements” on page 8).
• Inspect all hydraulic lines for kinks or damage. Replace any damaged hydraulic lines.
Symptom Cause Remedy
Jaw will not move, moves too fast or
moves too slow.
No hydraulic ow to the MDP or
hydraulic ow is too high.
Check the excavator hydraulic circuit
and ensure the hydraulic lines are not
kinked.
Check speed valve operation.
See “Adjusting the Speed Valve” on
page 23.
Jaws drift open or closed
Base machine valve is open-center or
is faulty.
Use a closed-center spool. Use the
base machine manual to check the
valve.
Speed valve needs adjustment.
See “Adjusting the Speed Valve” on
page 23.
MDP cannot process or hold material
in it’s jaws.
The material is too big. Consult the factory.
Speed valve needs adjustment.
See “Adjusting the Speed Valve” on
page 23.
Back pressure is too high.
Check all hydraulic lines. Ensure they
are not kinked and are the proper size.
Check the base machine circuit for a
restrictor.
MDP will not rotate or rotation is very
slow/fast.
Crossover relief valve is bypassing
oil or the manifold block has internal
leakage.
Replace the crossover valve. Replace
the manifold block on the motor
and check cartridge valve seals for
damage.
The rotation motor/gearbox is worn
out or has a broken output shaft.
Replace or reseal the motor/gearbox.
Jaw rotation drifts left or right.
Control valve ports are open with
spool in the neutral position. There is
leakage in the control valve spool.
Inspect the base machine hydraulic
system.
Crossover relief valve is leaking or is
set too low.
Replace the crossover relief valve.
The jaws don’t shift speed when
closing.
Pilot valve pressure is too high.
Adjust the pilot valve adjustment
counter clockwise in small
increments until issue is corrected
(see “Adjusting the Speed Valve” on
page 23).
Back pressure is too high in the base
machine return line.
Use larger diameter hydraulic lines
to minimize back pressure. Move
the main spool adjustment screw
clockwise in small increments until
the issue is corrected (see “Adjusting
the Speed Valve” on page 23).
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