Loader 2006 Jinma 284 Loader not lifting properly

[khanson2004]

Looking for some advice. I have a 2006 Jinma 284 with some hydraulic issues. The loader goes up very slowly unless you turn the steering wheel hard either way. I have recently changed the hydraulic oil and now the bucket dumps fine but coming back up to level is very slow and turning the wheel doesn't change anything.

What do you think is the problem? Pump? Proportioning valve? Air?
It does have an external filter in line. Does it also have one in the tank under the seat?

Any help would be much appreciated.

 

[piper184]

What weight of fluid are you using and what are your air temps these days?
Does it act any faster after the fluid has warmed up? If so, you might want to consider using a lighter weight fluid
Will the loader lift a load of 5 or 6 hundred pounds? If not, you might try increasing the pressure of the relief valve on the loader.
Will the 3pt lift a heavy load? The pressure relief valve for the tractor is located in the 3 point control valve and I think it is adjusted by adding or subtracting shims.
The diverter/priority valve is there to make sure the steering gets fluid priority over the 3 point lift and is in the circuit after the front end loader so it shouldn't have any effect on the loader.
I guess I should ask if this is the Jinma ZL20 loader?
The manual says it should lift 875 pounds.
Lift times (empty?) are listed as:
Raise 6.5 seconds
Lower 5.0 seconds
Bucket dump 5.0
Bucket rollback 4.0

These times seem backwards to me but considering the direction of the cylinder mounting this is at least theoretically correct. Maybe these should be listed as cylinder extend/retract times as the gravity acts on the bucket in the opposite direction.

If it is just the loader that is having problems there could be a partial blockage somewhere in the control valve or perhaps it is worn and leaking internally. The factory valves were less than "high" precision.