Posted for "Matt Hapgood" <matt.hapgood@alumni.duke.edu>:

 Thanks Mike,
 
 I tend to agree with your observations.  Vern has also suggested the
 possibility of a sticky spool valve.  I think I'll start by having the pump
 checked over.  Then start dealing with individual cylinders.  How do you
 check each cylinder?
 
 Thanks,
 
 Matt