re :
> Does anyone know if activating the start signal causes the ECU to
> output injection pulses regardless of the RPM signal?

I can't imagine that it would. There is a 'start signal' input to the
ecu , but for that  to  cause the injectors to get triggered without
also knowing that the engine is turning - that really would seem 'not
right' at all.
   Sometimes people crank on the starter for a minute steadily.  That
just could not work.

of course..if hydro-locked with gas ..
just remove the spark plugs to clear the fuel out, Crank it on starter
with a remote starter switch with fuel and ignition systems not on.

I had an ECU do exactly this in a 1.9 wbxr ...injectors on all the time,
as soon as you turn on the key.
I sent that ecu to David B. to look at ..
basically we decided it was junk I think.  He may still have it.

scott