<<  I had all of the problems with the hydraulics/pump that are being
posted
  recently and over the years.  Last August I replaced the original
pump (1989
  kit) and now everything works like a finely oiled system.  Yes, it
was
  expensive ($600.00) and a pain to reconfigure the installation but
all the
  hiccups and headaches are gone.>>

George,
I am not familiar with the older pumps, in particular on the inside, so
I can only speak to what I believe is the current configuration.  I
assume your old pump had the round cylindrical reservoir as shown in my
old building manuals.  The two pumps I own were purchased in '95 and
around '00 and are identical inside and out.  The Oildyne schematic
hasn't changed since then so I assume the currently produced pumps are
still the same and agree with the schematic.  There are factors within
each pump that probably influence this locking-up behavior, relief valve
settings for example.  When I swap pumps between the test bench and
plane, these settings have to be changed to compensate for the
interaction between the pump, relief valve, pressure switch and one
cylinder vs. 6 cylinders with 20 feet of hydraulic line.  Given the
rarity and apparent randomness of the event, it appears that a number of
parameters have to come together for the system to lock.  It took
several hundred hours for mine to lock-up for the first time.
Chris Zavatson