Good day guys, need some troubleshooting advice, Initially the excavator had swing problem where the pressure from the pilot manifold (that holds the accumulator, prv, and other solenoids) weren't sending pressure to the main control bank for the swing implement For the time being I used a Tee off the swing brake pressure that goes to the swing control brake valve on the swing motor to supply required oil flow and pressure to the MCV that requires that pressure and the swing responded well after. Tried some pressure test, Stick and Boom Implements stalled at 4200 psi Swing stalled at 3500 psi The travel need some attention, tried adjusting the cross over relief valve and most gotten from it; 3500 psi forward and reverse, left track and right track The bucket however, extremely slow cycle times and pressure readings less than 1000 psi while moving the bucket close or open I blanked off the lower pump NFC to a gauge, the bucket speed increased dramatically (the gauge would vary from 1800 psi to as low as 300 psi (nfc pressure) once moving the respected controls for that NFC) which i suppose to be good reading? When I blanked off the upper NFC to a gauge, the bucket speed slowed down (again, the reading on this gauge similar to as the upper pump - neutral; 1800 psi, function of the bucket lever would drop to as low 300 psi; nfc pressure) Tried swapping bucket relief valve with stick relief valve same results, (stick good, bucket no good) Looked at the regulators for upper and lower,, they're just as good as each other when opened up, nothing broken or worn out Oh, the machine has been down for years and we've just started to get her up and functional, hydraulic tanks cleaned out, new filters, clean strainer, clean new oil, no water, dirt etc... Any advice as what checks I should perform?
oh, just to clarify, when I blanked off the Upper Pump, the lower pump NFC line would be reconnected to the pump like it's supposed to, So basically when it's only the NFC at the lower pump blanks off then only would the Bucket speed increase...
Update, by interchanging the NFC lines between the upper and lower pumps, the bucket responded well after. Just curious if I can leave it this way? All other implements works fine without loss of power to the engine.
Good day forum, Could still use some advice on this problem With the NFC lines swapped between the upper and lower pumps; the bucket speed increased but the swing operation got slow instead... Tomorrow I'll reconnect the lines to it's original position and focus as to why the bucket operation won't upstroke the pump.... i do know the NFC pressure drops when the bucket control is moved, this would be good enough to upstroke the pump, or maybe I'm missing something else? If the pump were at fault, would it not upstroke with the other functions from the Right side of the MCV , the other functions seems to work fine concerning the upper pump Upper Pump -> Right Travel, Attachment, Bucket, Boom I, Stick II Lower Pump -> Travel Straight, Left Travel, Swing, Boom II, Stick I
Your machine is old enough that possibly there aren't many people with experience with your specific problem. An issue on only one function would lead me to start with checking all the possible issues that could happen on that one circuit. Does the bucket cylinder drift. Is using it creating heat or noise anywhere. Have you pulled and checked the return filter? Have you done any cycle times on the rest of the functions?
Make sure the hydraulic tank cap is on tight, the tank has to be able to pressurize or all functions will slow. The pump will starve for oil and cavitate.
Thank you for your replies, yesterday spent an entire day working with an old schematic of the system... that was torture following an old poorly printed black and white copy, but it was better than nothing. I retraced to my first initial problem of the Pilot Manifold that was not sending a pilot signal from one port, for those that may know of the trenching solenoid, (troubleshoot this valve and turned out to be faulty) Can't even get a replacement for it so I shifted the spool and locked it towards fully open. I did cleaned and tested all the other solenoid coils and valves. Changed suspected collapsed hoses (return from manifold to suction pipe on pump) and another hose to deal with the automatic change over valve, Well in fact I removed the entire manifold and serviced whatever that could be removed and cleaned in this small but seriously heavy block I also removed the negative flow control valves, had no seals on them, corrected that issue, also went ahead and pulled the travel straight spool and bucket spool checked for any issues With every check and test I did, I only saw a huge positive difference when I serviced the pilot manifold and manually opened that trenching solenoid spool. The pressure that wasn't coming through finally did came and the swing brake functioned as it should with it's original plumbing and at the same time the bucket function increased rapidly like it's supposed to. From this point; recalibrated the powershift solenoid, engine speed, performed sweep test on both, also before fine tune adjustments to the pump and she's working like a beast. First time I'm doing work on a machine this old, think it's a 92', good learning experience.
I don't know if this is any help. I don't know if it's any better than the paper one you have. Would a document explaining the system operation be of any use to you.?