As has been said, 1 pump goes bad and both motors are out.

Not knowing anything about all this, what of the opposite situation:
One engine has some different problem and is stopped. Does
the fuel pump still pump gas to it....or can some line shut-off
work to prevent that?

Also: On my mechanical fuel pump, there is a little manual
pump lever. To fill the bowl you can pump that by hand
instead of cranking the engine.

Gary