S0708460K
Page 15
Main Pump (Denison T6DMY Series)
TROUBLESHOOTING, TESTING AND ADJUSTMENT
The following table lists common difficulties experienced with vane pumps and hydraulic systems. It also
indicates possible causes and remedies for each of the problems listed.
It should always be remembered that many apparent pump failures are actually the failures of other parts
of the system. The cause of improper operation is best diagnosed with adequate testing equipment and a
thorough understanding of the complete hydraulic system.
Problem Possible Cause Remedy
Pump not delivering fluid. Driven in wrong direction of
rotation.
The drive direction must be
changed immediately to prevent
seizure. Refer to “Reassembly” on
page -22, for correct ring position
for each direction of rotation.
Coupling or shaft sheared or
disengaged.
Disassemble pump and check
shaft and cartridge for damage.
Replace necessary parts.
Fluid intake pipe in reservoir
restricted.
Check all strainers and filters for
dirt and sludge. Clean if
necessary.
Fluid viscosity too heavy to pick up
prime.
Completely drain system. Add
new filtered fluid of proper
viscosity.
Air leaks at intake. Pump not
priming.
Check inlet connections to
determine where air is being
drawn in. Tighten any loose
connections. See that fluid in
reservoir, is above intake pipe
opening. Check minimum drive
speed which may be too slow to
prime pump.
Relief valve stuck open. (Models
with integral relief valve only).
Disassemble pump and wash
valve m clean solvent. Return
valve to its bore and check for any
stickiness. A gritty feeling on
valve periphery can be polished
with crocus cloth. Do not remove
excess material round off edges
of lands or attempt to polish bore.
Wash all parts and reassemble
pump.
Vane(s) stuck in rotor slot(s). Disassemble pump. Check for dirt
or metal chips. Clean parts
thoroughly and replace any
damaged pieces. If necessary,
flush system and refill it with clean
fluid.
Insufficient pressure build-
up.
System relief valve set too low. Use a pressure gage to correctly
adjust valve.
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