Hi Guys I have the following problem on a JCB240 excavator when I stall arm out function my boom raises by itself and I cannot boom down while arm out function is stalled. I have done the following my pilot lines from the valve bank to the cushion valve have been checked and corrected according to the schematic supplied by JCB agents the pilot lines to the shuttle valve have been checked and corrected as per schematic form JCB agents. Please guys any information will be greatly appreciated. Regards Arnold
make sure on boom spool think might be two the allen key holding the spool return spring is tight as this will cause the spool to float as a thought.You can test this easy doing a neg control test on the machine with two gauges.