hi guys i got some trouble on this excavator hitachi EX120-2. The only slow fonction is the boom up and down, fuse ok pilot 700psi pilot sensor changed with the other one wire changed too relief valve changed with another one selenoid valve on the pump changed with the ohter one tried to change the hoses with another fonction but the problem stay at the same place boom up and down Spool is good too, All fonction work good but not for the boom fonction, any ideas? thank you
Welcome to HEF Field Tech ! Did you swap the cylinder hoses or the pilot hoses? Did you check pilot pressure at the pilot cap of the spool in question? If so and you have good pilot pressure at the cap you may be dealing with a load sense issue. Does the boom work faster if you operate another function? Does the boom work faster if you stall another function?
yess it’s faster when i actioned antoher foction, yess i swap the pilot hose and the pressure is good on the spool cap,
Sounds like a load sense issue. Look at this Deere 490E thread (490E is the same machine as an EX120-2, just a different engine). In that thread Lachau posted some really good graphics. Look at post #8. That is where I think your problem may be. HeavyEquipmentForums
Hi HEF have solve the slow boom issue. Its more on load sensing issue. Remove shuttle valve for boom. Just clean and check again.
Hi Field Tech, I am having the exact same problem with a John Deere 490E. Did you fix the problems on yours? If so, what fixed it for you?
Had same problem and if your looking for quick fix, unplug boom solenoid and boom should work again. hope this helps