Another quick update...
I now have a no-contact tachometer and was able to make an accurate measurement of the engine RPMs:
Idle = 1800-1850 RPMs
WOT = 3450-3500 RPMs
As for the hydraulic pressure at WOT, I'm still below 1000 PSI.
It's possible but it could be broken or the plunger stuck as well. More likely is the pump is worn. Is there a filter screen in the system? Also a collapsed hose can be the issue especially on the intake side of the pump. The outside of the hose can look fine but the inside can be restricted.
I have a filter on the return line, but there is no filter screen in this system. Hoses are all new 3000 PSI hydraulic lines. Now, I did change the feedline from the tank to the pump to a 3/4" hose rather than 3/8". I don't see how that would cause low pressure on the output side, but that is a change I made with this loader project.
The other thing I have not done is test a different port off of the control valve.
When I hit the limits and the pressure relief opens, I'm hearing the squeal at the control valve...I think. If the pump were worn and allowing bypass, wouldn't I be hearing something there? I have a stethoscope for finding bad bearings, so I may see if that can help me figure out the definitive location of the pressure relief squeal.
I can try to swap out the pressure relief parts - QCC quoted me $50. This loader project has already cost me a bit of cash...what's another $50?!?! The existing parts are 43 years old so new couldn't hurt. Then if my PSI is still low, the pump is the only thing left.
The good thing is that everything works, and I'm slowly eliminating any leaks.
Edited by zuren, September 10, 2020 - 08:08 PM.