Dake press hydraulics

Here's a picture of the Dake 150 ton press that I bought.

The way it works is that there is a reservoir of hydraulic fluid surrounding the ram, below the top frame. It has a weird hydraulic power unit on top, comprised of what seems to be a Bosch injection pump for a 6 cylinder diesel engine, ran by a 2 HP electric motor.

The pump draws hydraulic fluid from the reservoir, pumps it into the ram. The fluid can be bled back into the reservoir by a valve, and the ram retracts, due to a powerful spring inside.

The injection pump has an oil fill port (for lubrication, not for hydraulics) and was, ominously, empty of lube oil. I added enough oil.

I also re-filled the hydraulic reservoir with fluid. It was nearly empty.

The motor ran, however the ram would barely move. It would move, very slowly, about 1/2 of an inch, then it would stop. It would retract if I open the release valve.

Changing the rotation of the three phase motor did not help.

At this point, I stopped and decided to ask for advice on why it is not working.

I see the following possibilities:

Any ideas here.

I can easily replace the hydraulic pump on top, as I have a nice hydraulic unit that is good for 5,000 PSI. So if there is no easy fix for the top mounted unit, I can easily junk it. I wanted to know if anyone has experience fixing such presses.

Thanks