Have a cat 303.5 mini x that is having issues running a hammer attachment. Its the machine as the attachment work great on any other machine installed on. Checked psi at small valve bank fitting and it seemed low 250-500 when in full speed work. System should be around 3500PSI. I have not been able to get pressure reading down stream yet @ attachment. Plugged into Cat ET, found nothing. All other hydraulics seem very responsive and not lagging but when you use a bucket with a big load she falls a little. Per my knowledge, all points to a pump. But don't know that much about these mini x machines. Any help or pointers?? Serial #CAT3035ECJWY0075
Hammer circuit consumes most of the flow compare to other circuits. Seems like your aux circuit isn't building pressure, not the main pump (since other functions work fine). your cat has separate pressure/flow circuits - aux has its own relief valve, flow compensator, or priority valve that can fail independently of main boom/bucket circuits. Most likely causes: 1. Aux relief valve stuck open or set too low 2. Aux spool not stroking fully 3. Aux flow compensator failed 4. Check valve stuck at aux port Since your bucket "falls a little" under load, suggesting a slight pump wear or main relief on the edge. Not catastrophic but confirms system is marginal overall Do one thing. Test pressure directly at aux quick coupler under load (stall hammer). This confirms if pressure loss is at valve or downstream. Locate and adjust aux relief valve - turn clockwise 1/4 turn at a time, retest (don't exceed 3500 psi). Check pilot pressure to aux spool. It should be 400-600 psi when activated Don't replace the pump yet. Aux circuit issues are almost always valve-side on these machines. Focus on that aux relief valve first; it's probably your culprit.