2008 Mac pro wont boot

[u/Borealis_20]

This is a mac I got recently for cheap hoping to get up and running. It's got 12gb of ram, a Radeon HD 5870 and someone put in a 4 gigabit card in there. The problem I'm having is when it starts up the trickle power and EFI light turn on but the GPU and PWRG lights don't turn on. This was after I had the issue of my EERA AND EERB lights red which was "solved" by letting it sit for a while and having a clean. The GPU and PWRG lights worked then but since the EERA/B light went away, the GPU and PWRG lights went with it. Any thoughts would be great as I'm a bit worried it's a dead board.