If any pressure exists on the hydraulic system, the starter has difficultly turning over the engine as if the pump is under pressure. If hydraulic pressure is released on all cylinders, the starter has no problem. Is this correct operation for a 416c? thanks
no........
Any ideas on a possible cause?
From researching the functional diagrams, I suspect the relief valve in the boom valve segment could be the problem. I think the situation always ties back to pressure on the boom. Does anyone have any other ideas or agree with my suspicion?
It shouldn't matter about a load on the system. You have something causing the pump to stroke up when it shouldn't. Get a hose and a 6000 PSI gauge and connect to the pump outlet on the pump. Should have a signal and an outlet fitting. Outlet is the highest pressure and should be about 300 to 400 psi when not using hyd functions. If any spool is out of center the signal will come to the pump and the outlet will go up to maximum pressure. If this goes on long the hyd will overheat and melt the hyd tank. If you find more than 400 psi at pump outlet with all levers in hold try to find a lever stuck slightly out of center. Check backhoe controls for a pedal shaft stuck. Later Bob
Thanks Bob for the help. I think that the boom control valve is probably causing the "stroke up" situation.
Kind of think the cylinder which is not centered would start moving with the engine running. Put all the cylinders in mid point and let it run and find out which one(s) move.
Thanks for the input AllDodge. I did some testing yesterday but was unable to reproduce the "stroke up" situation. The "stroke up" situation is an occasional event. I don't have pressure gauges so I did what I could. I did not notice any movement in any spool with the engine running. I did notice dragging of the stick spool at certain times. It seems the spring would not pull the spool all the way to center at times. I assume that this may be the problem spool. I removed the spool and lightly sanded. The problem may have improved some but still exists. I tested the pressure on the spool spring and it runs around 22 psi to compress. Does anyone know the correct spring pressure? Part# 195-2406 Any suggestions on how to proceed?
I looked the part up and found there (I think) has been a part change in later S/N. SIS does not provide any info on the amount of tension the spring should have. I would call CAT parts department and ask them to provide input. Then talk to the service department and ask if service manager. Whayne Supply in KY has been very helpful on many occasions for me.