Good evening all, I have an old jcb 803 mini that I’m having a control issue with, the right stick operates fine (boom and bucket), the left stick only seems to work intermittently (slew, dipper) the dipper works very slowly and the turret sometimes does not rotate at all but when the boom is manipulated they come alive, this also applies to the 2 speed valve, when the boom is manipulated high range works but. The boom is very jerky as well. Is there a valve to the left hand control that can be adjusted?
Good day & welcome to HEF The description of this problem most probably relates to a non-return valve 2F, if this remains open it allows the swing pump to drain to tank. Activating the arm will pressurize the swing circuit. Unfourtunaly I do not have a good illustration of his valve however if you locate the link line between the the MCV,s . If my schematic is accurate the non return valve is a external component to the main valve chest. This may not be the case if you are finding it difficult, take some photo's and I will try to help some more. Kind regards Uffex
Thank you for the quick reply! I have a service manual for the machine, I see the 2f circuits in this diagram, are these the small aluminum blocks? I was able to get some pictures before I left for work, Thank you again
Good day I cannot see the part in the photo's, please look for a main line connecting the two M ain C ontrol V alves, I would guess in that line you will have a coupling similar to No.8 in the illustration attached. Often there will be a check valve symbol etched into one side of the valve. Kind regards Uffex
I looked all over the valve blocks that I could see and couldn’t find anything that looked liked a relief, do not have those fittings, are these black capped pieces in the pictures reliefs? There was one by the dozer arm that I undid and tightened and it sped the dozer up. Thank you
The service manual says the one I fiddled with was the main relief valve, it did not seem to effect the swing or dipper action.
Good evening, I spent a little more time with it tonight and adjusted the screw on the right in this picture half a turn, the left stick now works correctly, the service manual calls this “1A servo pressure maintenance”. Is it safe to do this or is it possible that it creates excessive pressure? Thank you
Good day It is possible that the schematic is badly represented and the valve I am suggesting is housed in the return segment of the MCV, do you have a parts book for the machine? Kind regards Uffex
Good morning, I do not have a parts book only a service manual, I couldn’t find anything that stood out as a check valve on any of the lines, I looked on the valve block for brass fittings as well. There have been quite a few lines replaced on the machine, maybe it was lost? Thank you
Good day A line that has been replaced discarding the valve would explain the problem, I will try to get hold of a part's illustration to get us on the right track. Kind regards Uffex