Posted for "Christopher Zavatson" <Christopher.Zavatson@udlp.com>:
Hank, Scott,
Adjusting the pressure switch upward can mask another root cause for
this symptom, a spool valve that is installed backwards.  I have already
come across three Oildyne pumps which had the valve installed backwards.
  If this is the case, the low pressure side will not dump freely to the
resevoir, but must be forced past the relief valve.  The up side has to
fight the down side pressure.  The net working pressure is equal to the
high side minus the low side when the pump shuts off.  That is why the
gear does not make it all the way up.  The bumping is caused by the low
pressure side slowing bleeding down past the relief valve.  This then
relieves pressure on the high side until the pump cycles on again.
You need to see if your low side is remaining pressurized to find out
if the spool valve is in backwards.  Either check the low side with a
pressure gauge or see if your down side pressure switch remains open
once you have selected gear up.
Increasing the up side pressure setting will get the gear up by brute
force, but you will be covering up the problem.  The real downside to
this is that if you select gear down right after the gear has come up,
you will have to wait until the pressure bleeds down on the low pressure
side before the low pressure switch will close again.
Chris
N91CZ
360std