Hello, I’ve recently bought a 420D IT, BLN06042. After replacing a chunk of the wire harness to get the water temp gauge functioning I started my first project. I’ve noticed the boom function is extremely weak, I cannot lift the back of the machine up with it. The stick also seems weak but not as bad as the boom. All other hydraulic systems seem to work well. Does anyone know where to start troubleshooting and have a hydraulic schematic available? Is it possible the cylinder itself is the problem?
Start checking pressures on the functions. Chances are they'll be low if the hydraulics lack lifting power. Could be as simple as adjusting the reliefs or it could be something more serious. But that's where I would start.