MF165 rear links lifting while using log splitter

I have bought a second hand log splitter for my Massey Fergusson 165 and added some hydraulic fittings to the rear of my tractor to use it.
I have a Bare-Co B5210 divertor/isolator valve and used the previously plugged output to be the input for the splitter. I have used the return based on the left hand side below the seat and above the PTO lever.
When the divertor is "right" the front hydraulics run the front end loader control valve next to the steering wheel.
Whe the divertor is "up" the coupled fitting the feed the rear connected log splitter works.
When the divertor is "left" the rear link lift.
Every thing works in isolations althought the splitter isn't as powerful as it was when I tested it on a smaller ford tractor prior to buying.

My problem is that while using the splitter the rear links lift slowly. If you struggle on a piece of wood the lift faster. Once the links are all the way up the pressure to the splitter doesn't increase.
Hopefully a fix to this makes the power of the splitter increase. My theory is that the return I'm using mean the rear links are getting pressure. Have no idea how to fix that thought.

Help!

Your Bare-Co valve is not compleatly shutting off the oil supply to the lift cylinder and letting some oil leak past and raise the linkage.
Is the valve moving full travel? If you think it may be back feed from the return, then put the return line thru the gearbox filler plug and
see if the trouble goes away, if it does then an adaptor fitting can be put in the filler plug

Thanks for the ideas. I have replace the Bare-Co valve with another new one because I noticed it was leaking a little oil near the handle. it was always a bit loose
feeling anyway. That made no difference to the pressure or the links lifting.
I feed the return through the oil filler location next to the gear sticks but unfortunately that still made the links lift.
I read something else somewhere on these forums about putting your links up, locking them there with the valve so they are already pressurized when you use something
else. I don't mind the links lifting but the splitter seems to be losing power when they do and once they are all the way up it doesn't get better.
Ideas?

How good does the 3pt work? It should be able to lift 3600lbs, could have a weak bypass valve on the hydraulic pump. The stand pipe could be leaking, or worse case scenario a weak hydraulic pump.

How good does the 3pt work? It should be able to lift 3600lbs, could have a weak bypass valve on the hydraulic pump. The stand pipe could be leaking, or worse case scenario a weak hydraulic pump.

(quoted from post at 12:33:57 10/01/16) How good does the 3pt work? It should be able to lift 3600lbs, could have a weak bypass valve on the hydraulic pump. The stand pipe could be leaking, or worse case scenario a weak hydraulic pump.

Click to expand...

The Hydraulics would lift 1000kg (2200pds) I think. I'm not sure what the "stand pipe" is? Could it be the pipe that the divertor/isolator valve sits on top of?
There isn't any oil leaking from anything. The oil pressure gauge sits on 1/3 to 1/2 mark and the dipsticks for the engine and hydraulic sumps are close to full mark.
I'm hoping its nothing as serious as the hydraulic pump as that sounds a bit scary to fix.
All help is very much appreciated.

The stand pipe is the pipe that runs from the pump to the diverter/isolator valve. The MF hydraulic pump for the 3 pt only puts out around 4 1/2 GPM, what model of Ford tractor did you test the splitter on?