Have two 988H with that no longer hoist boom and curl bucket at same time. both are BXY prefix. Both issues occurred with in the past month. pump will maintain 4000 psi. boom and bucket sensor calibrations have been completed. all pins are tight and sensors are not seeing any slop (unexpected movement) Does any one have any ideas what would cause the machine to NOT perform two functions at once? The boom will raise with no issues but as soon as you attempt to curl the bucket back while boom is still raising the boom will immediately stop. As soon as tilt lever is released the boom will resume raise. PLEASE HELP!!!
Hi does the bucket tilt back while this is happening or is it stopped as well mark
You say you have calibrated the linkage sensors. Did you also calibrate the hoist/tilt control lever position sensors and the proportional solenoid valves at the same time..? Also have you tested for cylinder drift..? Although TBH if a cylinder is drifting you would not be able to perform the proportional solenoid valve calibration.
Curl continues lift stops.
I preformed the calibration of main control valve tilt and lift and controll calibration. While preforming calibration if cylinders would drift outside of the range it kicks you out and throws a trouble code. All calibrated successfully.
Checked relief pressure with boom at top of stroke, 4800psi. As soon as tilt is engaged pressure drops to 1100psi. Schematic shows that hydraulic flow goes to tilt then hoist, could pump have psi needed but low flow? When tilt is used could it be robbing flow from hoist?.
Thanks for confirming the info regarding the calibrations. I've seen it before where cylinders leaking internally could cause all sorts of weird things to happen. Do the 2 machines happen to be equipped with ride control by any chance..? If they are, have you tried turning it off or even better blanking the lines, just in case..? Sorry for all the questions but your OP said the pump would maintain 4000psi, then in post 6 above you mentioned 4800psi. Can you confirm which of the two values is correct. Also please be careful when testing the relief valve with the lift cylinders fully extended, a better way is to power down the hydraulics, it puts less stress on the lift cylinder head bolts. Another suggestion to see if your pump is giving adequate flow is to do a pump performance test. The pump is a varaible displacement and the possibility exists that it may not be fully upstroking. With a full bucket and at high idle engine RPM the lift function should raise the bucket from fully lowered to the kickout in approx 8.5 secs. While you have it up there rack the bucket all the way back and then with the engine at HI dump the load. Full rackback to full dump should be approximately 3.0 secs. Are the machines above or below BXY4000..? The implement hydraulic systems are a bit different depending on S/N.
Serial numbers are Bxy00678 andBxy01480. Relief pressure is 4800 at top of cylinder stroke. Tilt and hoist cylinders have been rebuilt. Never thought of lowering hydraulics to check relief psi, the book says to check it with cylinders extended; great idea! Thanks. Not sure if I understand the pressure drop from 4800 to 1100 when tilt is racked back? Is this action due to pressure reducing valve and can it be adjusted for better performance?
Oh forgot, no ride controll on either machine.
Try the pump performance test from post #7 above and see what results it gives you. The spec for the relief valve setting is 4500 +/- 90psi BTW, so at 4800 you are actually 200+psi over spec provided of course the gauge you are using is guaranteed to be accurate, or are you doing the test using the onboard lift circuit pressure sensor..? Did the problem start after the rebuilt cylinders were installed by any chance ...?
Problem started before cylinders where rebuilt. 5000lbs manual gauge, not top of the line so might be off some.
Never thought to ask before. Any oil analysis results available..?
678
1480
That first one has what I would consider to be reportable silicon presence (18ppm) on the last sample. Although the reports mention Particle Count there does not appear to be any numbers to back up their comments, unless they are another part of the document. Generally those oil anlaysis results don't look too bad.
Having had the rest of the weekend to think about it I'm still of the opinion that a pump performance test (post #7) might just reveal something interesting.