connecting 2 macs

Hopefully someone can help me out here. I have an older G4 which I've been having problems booting it up so I'm trying to connect through a firewire to an Imac. (basically i just need to grab some files off of it, and i want it to show up as an external drive). It's not showing up as an external at all and I've even tried going through Target Disk mode but it stays on the gray screen with the firewire symbol.
Am i forgetting to do something or does anyone know how i can get this to work. Any help is appreciated......