If you built a dam behind the oil reservoir would the pressure be the same? lol. Jeez, first you stir up shit over the fish tank.... now this!
Actually, I just went through this on a Tree mill that had no oil flowing. The problem was all the check valves were 100% clogged. The more I learned the system, the less of a surprise that is considering how small the passages are in the valves.
Usually, the valves are in an accessible place and the final outlet is just the end of the pipe so even if you can't access it, it's not gonna be the problem. But that all depends on how the machine was made.
BTW the Bijur manual says it puts out 60PSI. Even when I hit my valves with 125PSI of air they stayed stuck....not a speck of oil flow. Tossed them and installed $180 worth of new ones from Ebay.