Mark,
The result would depend on the pump. In most cases the flow control valve is simply an adjustable 'leak' of part of the pump output back into the tank.
1] Replacing the control valve wth a strait-through pipe between pump output and machine output would result in the pump delivering pressure up to the setting of its' internal bypass.
2] A blanking at this point would have the same effect but with no output from the machine.
3] A blanking on the return pipe would have the same effect as having the flow control valve on the full-pressure setting.
The reason I wrote "in must cases" is that it is possible to set up a system with a non-regulated pump (no internal by-pass) and to compensate with a flow control valve that had a limited range. I know of no commercially produced CC machine that has this set-up, but in such a system pump damage/burst pipes could result from setting 2] & 3] above.
John.