CA Hydraulic Pump Priming Method

Status Update:  The AGCO guy found a burr that was messing with the control valve operation.  He also replaced the broken control valve spring with one from a WD pump.  The broken one (what was left) was about 4 inches in length.  Supposed to be 7 inches in length per one source. 

Anyway, although it took a considerable time to prime, it now raises, slowly, but does not seem to want to lower as long as the pump is running, although with the control lever down, you can apply quite a bit of force and push it down part way (with pump running).  It goes down fine with the pump not running and the handle down.  Initially, with the handle lowered, it slowly crept up.  It seemed to get slightly better as the test progressed.  With the handle all the way up, it seems to be applying maximum force (even if that may be a diminished maximum).

He did not replace the gasket on the front end (flow control adjustment).  He thought it would not leak there, but leaks quite profusely.  Also leaking around the check valve fittings.  I suspect he didn't tighten them or the copper seals need replacing.

I've seen postings with similar behavior, but haven't had time to review.  Ideas?

Status Update:  It seems that the control mechanism is mal-adjusted.  I'm unsure where adjustment is needed.  The pump works best (full pumping force) with the traction booster lever just before the lock hole.  With the knob in the lock hole position, the main control works as follows (hold valve disabled):  Maximum lift occurs just before the full up position. This might be ok, with the slide/guard installed.  However, in all other positions, there is a slight lift action.  There is no lever down position (below the maximum lift position) that does not exhibit at least some lift action.  The only position that releases the lever arms is full up, just beyond the max lift position.  With the traction booster lever in the sweet spot (just before (to the rear) the lock position), the pump exhibits what I would remember as full pumping force.  It seems to have a pretty strong lift.  So I think the pump itself is fine except for some mal-adjustment (or assembly order problem).  I've had the thing apart 4 times and reassembled with all parts in the order specified in the I&T manual (I think).  The AGCO guy did the same thing last.  They at least have experience doing it. 

I've exhausted my time this trip.  I'm considering another trip in Nov, and/or taking the tractor to the (former) AGCO place. 

Additional progress.  I've discovered two issues with the hold valve.  

1) There were no spring shims on the adjustment screw so the spring was not making contact with the check ball and caused it to chatter in the full out setting.

2) After adding a fresh detent ball bearing and cleaning up the sticking spring, the outward pressure on the cam plate increased and the clip and washer on the left side (non-control lever side) were not pulling the cam in quite far enough.  So it was not changing setting because it was riding outside of the channel.  There isn't very much room for error.  Too thin of a washer and it doesn't pull in, too thick and you can't get the clip on :( I used a different style clip this time that seems to be holding it in place better than the E clip.  At least I know what to look for.

As far as I can tell, (with adjustments for hold testing) the plate orientation is correct but I'm not fully sure of the behavior.  Unless the check valve is overcome by pressure going up, it seems that the "hold" check detent position (and full up position) would prevent the right port (left cylinder) from lifting.  At least it seems blocked with light air pressure, but it is against the check spring which is supposed to block down not up (I think).

I hope to test again soon but I need to let some sealant dry.

Winter storm is roaring this way, so this was the last 70 degree day for awhile I fear.  I'm not looking forward to working on it the rest of the week :(  But I do have some boring hole drilling things I can do and stand in one place by a heater.

No change in behavior.  It goes up perfectly in the lift position.  But it goes up (slower but still fast) in all non-full-up lever positions (drawbar control is disabled and in the lock position) and all screw adjustment settings (per the manual...and beyond).  In full up position, it behaves correctly with fast strong lift even at idle engine RPM.  I know the hold valve is open in the full down or thumb screw lock position (closed in the detent ball position).  I think I have to assume that the control valve itself is not shutting off fully.  AGCO guy said it was sticking and that he fixed that.

On the bright side, I got ALL the leaks fixed (until it comes apart again :(.  The copper sealing washers for the outlet check valve caps were not crush washers like I thought, they were just severely deformed copper washers.  But they cleaned up nicely and are now sealing.

Given that my trip is about over, I'm inclined to take the tractor to the AGCO guy and let him mull it over for awhile.  This long distance renovation work is a pain in the rear.