Firewire drive - Not recognized when Imac already on

[matteusclement]

I have my imac running
my fw external drives are off
I turn them on.
sometime they pop right up, sometime they don't.
why is that?

 

[satcomer]

Disconnected the Drives and and Reset Your Pram. Then once you boot back up try to connect the drives and see if it works now.

 

[matteusclement]

no dice.
To be clear, it is when I have my imac already running and I have to eject them for some reason I try to plug them back in and they don't show.

IS THERE A WAY TO RECONNECT THE DRIVES WITHOUT PHYSICALLY UNPLUGGING AND PLUGGING THEM BACK IN?