Just over one year on —- Yes I know this is an old thread —
However, I was having problems with leakage past the end cover gaskets plus the wells filling up when stationary.
So, the pump comes apart, the ends are converted to “O”ring seals beaks removed and ball valves re seated.
All reinstalled only to find one side behaving as it should, the other seeming to be unable to pump the well dry.
I tested the pressure required to overcome the non return valves and found the working side was at less than 2 psi, the none functioning side needed in excess of 30psi to overcome the valve.
I doubt the pump is perfect, so I removed the NR valves and re-tried the system.
Everything seems to work as it should, when running the engine sucks the oil from the pipe, the wells empty.
I am running without glands, just using lip seals, I also run nylon tube so I can see what’s going on.