Deere 50D Slow hydraulics at all engine speeds

[Toddgarage]

First post, long time lurker and I want to thank you all in advance for your advice!
Deere 50D (gen1), 6000hrs, engine runs strong, and machine runs strong until a few weeks ago. The machine sees regular use and some abuse, but on average well maintained. We noticed the rotate function was slow and the forward/reverse travel speeds were also slow at all engine speeds. (tracking forward, moving the throttle up or down will not change the travel speed, the engine does not struggle either.)
A few weeks pass and the machine is sitting in the yard. Another guy mentioned the problem went away for a few days but has returned. I use it to smash the dumpster now and the same slow functions are present. Even the boom/jib/bucket seem slow at all engine speeds. One guy explained it "its like the main hydraulic pump doesn't swash and ramp up"
Fluid level correct, Hitachi oil (zinc free) always used, no leaks and no visible damage. No pressure readings yet. I want to carefully address the repair before applying the expensive parts cannon at it.
plan is:
Inspect suction strainer. Inspect main filter. Inspect pilot filter. Check fuses and relays.
Let's say those all look good, where would you guys start? Is there a priority valve? Hidden strainer filters? Electric solenoid for a main control valve to activate the main hydraulic pump?
Cheers Guys and thank you. (i'll be at the machine later this week, so specific questions will take me a day or 2.)

 

[Toddgarage]

Additional info: This has 2 speed travel. Another operator thinks the travel speed does adjust up and down with throttle selection. It's possible it was in rabbit vs turtle. I will double check the travel speed in both high/low at all engine speeds.

 

[muddog1975]

I'm not familiar with this machine. But get the specs. On hydraulic pump pressure, then test your pump pressures. Sounds like it's worn not producing enough pressure, with all hydraulic functions being slow. Seems likely, with 6000 hrs on it. Good luck, let us know what you find.

 

[mg2361]

Machine serial number.

With track off the ground, record from a running start the track cycle time in 3 revolutions. Fast idle, 120*F oil, travel speed fast (rabbit). Do that for both tracks. Post results.

Then need to check System pressure at both pumps (arm for pump 1 and bucket for pump 2)(3684—3974 psi, fast idle, oil @ 120*F), pilot regulating pressure (at pilot filter, 885-1030 psi, fast idle, 120*F oil). Pilot actuation pressure at the spool (305-493 psi, fast idle, 120*F oil).

Inspect suction strainer. Inspect main filter. Inspect pilot filter.

Make sure to cut them open to inspect.

 

[Toddgarage]

Thank you. I’ll test travel speed today with the tracks elevated off the ground. I did confirm the travel speed on the ground in both low and high are still slow regardless of of engine speed. However, the machine oil temp was probably ambient air temp of about 80.

 

[Toddgarage]

Tested travel speed with tracks suspend; idle vs full throttle. It was about 1/2 second faster at full throttle, well within the error of us using the timer on the phone.
I don’t think the pump is weak because it was able to pick itself off the ground for the track travel test without issue.
S/N 50Dx245484
Haven’t had time yet in the shop to check filters.

 

[mg2361]

What was your fast idle cycle time?

 

[Toddgarage]

The cycle time is the almost the same at idle and full throttle. It took the tracks 16.5 seconds to make a full lap at both idle and full throttle.
Update:
I pulled all the fuses and checked them, put them back in and the problem has been solved. Now I’m going to try and chase down which circuit it was. My first guess is the solenoid near the pump and this small inline filter housing. Pilot filter?

 

[Toddgarage]

Conclusion:
Pulled the fuses and found none that were blown. This however did fix the issue!!
This machine has an engine monitor and automatic idle down controls. The best reasoning we have is the control modules, interface and gauges got a reset when all the fuses got pulled out.
The engine speed can be set to max and if the machine pauses for with no operator input for 5-10 seconds the engine speed drops to idle. As soon as the operator moves the controls the engine will ramp back up to max throttle and work can continue. We think this system also unloads the main hydraulic pump to prevent the engine from stalling while idling down or ramping up again.
I don’t know exactly which module it is, or what solenoid is responsible for this action. But it’s fixed!

 

[muddog1975]

Glad you got it going!