Puzzled with an issue I've run into with a Hitachi EX120-5 that I have. Machine was running fine when parked, fired it up a month later and the hydraulics are non responsive. Played around with the Pilot Shut Off Valve and confirmed that the arm is controlling the linkage, and the valve body is being rotated in the housing. Strangely the first time I tried messing with this, the thumb function worked (although super slowly) but responded to the Pilot Shut Off valve being operated. Meaning it only worked when the valve is closed, leading me to believe the valve is functioning. However tried it again today and no thumb. No boom, stick, bucket or track functions are currently working. Machine still starts up immediately, and seems fine otherwise. Any suggestions on where a guy should start to look? Was thinking the Pilot Solenoid valves might be stuck. Thanks!
Please check the pilot pump pressure with a gauge; it should be around 40 kg/cm². Also, verify the Pi1 and Pi2 lines from the Control Valve to the Regulator by disconnecting them and directing them into a hydraulic oil container to check the flow. English is not my native language, so please excuse any mistakes!
Welcome to HEF BCman . Whats the sn # prefix 1E4 or 1E8 ?
thanks for helping out.
Verify pilot pump pressure first, as low pilot pressure (typically 30-40 bar) prevents main control valve spool shifting. Test at the pilot pump outlet and after the pilot filter using a gauge, clogged filters or worn pumps are common after inactivity. Inspect hydraulic oil level, condition, and filter status; contaminated or low fluid from sitting can cause system lockup.
1E4. Not 100% sure of the year
I don't have a gauge to verify pressure, but i have a friend bringing one out. I did pull the two pilot solenoids today and cleaned them. Both were stuck and fairly gummed up. However no change when I reassembled. I also checked the pilot filter, and pulled apart and cleaned the Pilot Relief Valve. Similarly no change. Cleaned the two pressure sensors mounted on the hydraulic tank and the ones in the shockless valve. No change. A friend was able to confirm hose movement at the shockless valve, with different hoses moving depending on function input. So that makes me think the pilot system is working and producing pressure, but for some reason the Control Valve isn't doing anything with those inputs. Oil level in the tank is right between the lines, and the main tank filter was replaced 150hrs ago. It was only sitting for about 6 weeks when this issue arose. Thanks all for the help!
Also confirmed voltage at the Pilot Solenoid Valves and checked all fuses.
1E4 is a machine intended for the Japanese market. The Main controller controls the ground side of the pump pilot control solenoids. As already suggested , check the pilot pressure. If the pilot pressure is good, as a test you can temporarily eliminate the pump pilot control solenoids by feeding the hydraulic pump regulators directly from the pilot pump outlet tee.
Disconnect the hose going from the solenoid valve to the Regulator. Then, connect the pilot signal line directly from the Control Valve to the Regulator. I tried this fix a few months ago and it worked perfectly. Good luck!