I wrote this post last fall and all I did is put the new glow plugs in and everything seems to work fine. Thanks for the feedback. It might help someone else down the road.
My operation and maintenance manual for 773C with V2203E engine shows 15.0 GPM @2850 RPM and system relief at quick couplers is 3000 to 3500 PSI. I do have the Service manual which is for a V2203EB and the RPM specs for it is max 2800, high idle is 2950-3050 and low is 1125-1175 RPM
What I am trying to say is that the valve assembly is your diverter valve. I'm not sure what the aluminum one is, I don't have that on my 773 . You could be right . That looks like a Hydraulic pressure relief valve. Must be handy for when you need to relief pressure out of the system.
It could be the control module is defective. I've had that problem before. Everything was working except the auxiliary part. Took me a long time to replace it because there is no way to diagnose the control module .unless you can switch it with one that is working. I checked everything I could...
I believe the diverter valve is right there in your own picture where you are showing the loose wires. the loose wires are from 2 solenoids and the solenoids are mounted on the diverter valve. I'm not a mechanic so I'm not 100% sure.
Do you know where the Control module is? I circled a plate on your picture. The control module is on the opposite side of the machine. Identical plate. The control module is mounted underneath it.
I'm trying to send you the wiring section of my maintenance manual. Not sure if you have this. You'll see on the upper right corner of the wiring diagram where the 2 solenoids are the wires go from them and splice into the joysticks and onto the control module