We purchased a used GP Air Seeder a couple years ago.  At first we hooked it up to a Case 7240 and it would not lift it.  Messed with the compensator valve to increase pressure and removed the weights.  We managed to get it to work but it raised very slowly.  We then purchased a Cat55 from the same owner we bought seeder from and he said he had no problem.  The Cat was better but still agonizingly slow.  Now today it will not lift it more than 6-7".  The right wing was all the way down.  We took a payloader and took some of the weight off to where it would raise fully so we could rephase the cylinders - which it did.  The unit is level.  But it will still not lift it by itself without the loader.  I do not think it is practical to have a loader follow the seeder around the field.   We hooked up a high pressure gauge with a tee to see what the pressure is.  It would not go above 1550psi while lifting the seeder.  For grins we hooked it up to the wing fold side and the pressure went to 2850 when the cylinders fully stroked so I know the tractor has sufficient pressure (GP told me it should only require about 1700 psi).  There is a non-adjustable relief valve in the system so we installed a new one - no difference.

I am thinking we have a leaking cylinder and oil is leaking past the piston to the point the pressure will not build enough.  There are 6 cylinders with 3 on each side (main - on a rockshaft), rear and wing.  Each cylinder is a phasing cylinder with each one sequentially smaller - as it should be.  Phasing ports are on the correct end.  If I do have a leaking cylinder I can't quite figure out how to figure which one it would be to cause the symptoms.  Any suggestions would be appreciated.  Tomorrow we are installing a new seal kit in the cylinder that drops over time.  It does have some tiny bits of metal in it but other than that no real evidence of a big leak past the piston seals.  No idea where the metal bits may have come from.  Oh, at some point in the past the cylinders were all rebuilt based on a sticker attached to all the cylinders.