Randy,

<<I am absoluteley baffled over how both the high and low sides build pressure during flight.
Thoughts?>>

Your case is somewhat perplexing.  The retention of pressure would indicate a reversed spool valve, but only seeing 200 psi during retraction does not.  If the system only retains 200 psi (normal while pumping), how does it retain 600 psi while static?  What bothers me is that the fundamental purpose for the back pressure circuit is to relieve pressure on the low side to avoid tripping the pressure switch

 

As an aside, I always view pumps coming straight from Oildyne as suspect until operational tests confirm correct assembly.  Back in the '98 time frame, I had my pump in for servicing - I let it run dry while working on some cylinders.  Their shop manager called me to find out why my spool valve was in backwards.  After several minutes describing the hydraulic system to him, he determined that my 'backward' spool valve was actually correct.  The build instructions were wrong.  Low and behold, one pump after another in the field started exhibiting the symptoms of a reversed spool valve.  I don't know if the paperwork ever got fixed.  Even the pump I had borrowed while mine was out had a reversed spool valve.  I had to crank up the high pressure side to get the gear up all the way.  Are you able you retrieve a part number off your pump?

 

Chris

 

 

 

 

Chris Zavatson

N91CZ

360std.