You're saying that the fuel primer bulb pumps up hard when connected directly to the carburetors... BUT... does not get hard when connected normally to the VRO as it should be?
If so, that indicates that a faulty diapragm within the VRO is allowing pressure and fuel to flow from the VRO thru the line that leads from the VRO to the crankcase. Remove that hose from the crankcase (or the VRO) and observe it while someone else pumps that fuel primer bulb.
However, if this is the case, I don't see how the engine could run at all with a problem like that.
What do you mean by the "Fuel Pressure" alarm goes off? There is no fuel pressure alarm on that engine.
There is:
A combined overheat and fuel restriction alarm... constant steady beep.
A low oil alarm... a beep every 20 seconds.
A VRO failure, no oil alarm... a beep every other second.