Troubleshooting Hydraulic Issue - Yanmar

[K20017]

Hello, have an issue I've been troubleshooting but can't seem to pinpoint the exact issue or a simple way to do it.

Machine: Yanmar Vio40

My stick cylinder moves very slow and with little force on extension but works just fine on retraction. I have a gauge hooked up to the outlet of the pump line and display it in the video. The cylinder will also move by itself until I hit the stick the other way. The short length of the lines prevents me from swapping lines to confirm it is not the cylinder but I don't think it is that anyways. It is the only thing on the machine that is not working so it is isolated.

Here is the video showcasing the issue: https://photos.app.goo.gl/P8Li1mzQDgKmroAS9

My thoughts:

Relief valve: If it's stuck open, it would be venting pressure back to the return with little operating pressure
Spool Valve: Would this explain the thing moving on it's own if the internal seal is bad?
Pilot pressure?

Thanks in advance.

 

[heymccall]

My first thought would be the centering spring on that spool may have a loose bolt, or even a broken spring. As for seal in there, there are none on the spool. The spool is precision machined to its bore.
If it were the relief, it wouldn't move on its own.
The fancy bolt thing at the arrow.
Remove #10 cap and inspect.

 

[K20017]

Thanks for the quick reply.

Would this broken spring also cause low pressure? Before, I had the issue where the retraction would be very slow or just stop working completely. Then it seems to have swapped to the extension side.

Also this is a 40-1 model, grey market, and finding a service manual seems tricky. The 40-2 model is sold in the US and I imagine is nearly identical to mine so I figure that would be my best bet. Where would one look to get a copy of one of those?

 

[uffex]

Good day
Attached may be of help.
Kind regards
Uffex

 

[K20017]

Thanks, that certainly describes my symptoms!