Early 1990's vintage, sn 133-2989, no pump electronics. When bucket function is combined with stick in or out, boom up, or swing, bucket speed increases dramatically. also if left track is slightly actuated same bucket / swing higher speed results When bucket curl / uncurl and swing functions are combined both circuits have dramatic increase in speed. Bucket only actuation at high idle - curl 9 sec, uncurl 7 seconds Swing only actuation at high idle - 24 seconds for one revolution, either direction. When both functions above are combined speed improves for both, bucket curl 4 seconds, uncurl 3 seconds. Swing speed 7 seconds for 1 revolution- very significant improvements in speed. Has three solenoids on pilot hydraulic circuit. two solenoids are for engine speed control, this is disabled. One solenoid limits pump stroke, this has been hydraulically disabled by running pump controller line back to pump suction to ensure full pump stroke can be achieved. Hydraulic pump configuration is 2 pumps within 1 case. One of the pumps had severe elongation of piston barrels, piston bores were oval shaped instead of round. Entire pump assembly refurbished and bench tested at hydraulic shop. I suspect this damage was due to improper system setup. Hydraulic tank drained and flushed, hydraulic cooler removed and flushed. I realize that there is some material from the pump failure in the system but there was very minimal material in the valve body when it was diss-assembled. Went through the flow sensing pressure feedback adjustment procedure and pump pull down checks. Tracking is straight and tracking speed is acceptable. Pump pull down adjustments used to attain equal tracking speeds. Removed the main valve body to inspect. Found a couple if spools were stiff to move, don't remember which circuits these spools were in. After working / cleaning all spools moved freely, no damage observed on any spools. Swapped boom and bucket pilot connections at main valve body, no change in bucket speed. Boom speed also not affected (still normal). Makes me think pilot circuit is OK Bucket circuit has 2 check valves located in the main valve body according to the manual, both have been inspected and appear ok. System pressure at 4200 psig at each end of bucket cylinder travel Boom speed, stick speed and travel speed are about right, just seems very odd that the bucket and swing functions are very slow when actuated alone, and very fast when actuated together. Appreciate any help on this.
You may want to investigate the load sense piston in the pump regulator. I've seen them seize up and cause similar symptoms.
Thanks for commenting. I feel confident that the shop replaced the rotating assemblies but not sure how well they went through the control side. We haven't looked into that part of the pump. Looks like we can remove those parts without going all the way into the rotating side. Just seems strange that other functions work well and two do not.
Found I had swapped load sensing feedback hoses in earlier troubleshooting and must have forgot to swap back. Bucket and swing functioned correctly. went through all relief valves and adjusted all per the manual. Used machine for about 2 hours with no issue. after 2 hours began noticing engine bogging down. Fuel was verified ok. began adjust pressure feedback and forward pump horsepower limit, eventually adjusted to opposite problem, now issue is front pump will not upstroke, leading to slow bucket and very slow right track. Pulled pump and noticed forward pump was not at full stroke when viewed through pump suction, rear pump was at full stroke. when pump regulator end was loosened observe forward pump stroke go to full stroke (spring position). Pump regulator appears ok, all is clean, spools are free. Inspect swash plates and find some scoring, maybe explaining why forward pump was initially not at full stroke when pump was removed. The fact that the forward pump was not at full stroke when pulled but then popped to position when the bolts were loosened seems to be pointing to an issue with the clearance of the forward pump swash plate. Anyone know how this clearance is set? I believe this is a rexworth 8V86 pump.