amd 6750 no boot issue

Hey guys im sure theres a post somewhere about this stuff but im on my phone and its kinda a pos to surf the net on but I just bought a amd 6750 to be able to play diablo 3 on this pc my issue is when I install the video card and connect the 6 pin adapter I can turn on the pc and all fans kick on even the gpu but I get no signal if I take out the card itll boot just fine ive tried even putting the card in and connecting via motherboard and still nothing the only two assumptions I have is the power supply cant handle it or the video card is no good. So if you guys can give me your thoughts on it that would be great

I doubt it makes a difference but its plugged in via hdmi its the only way I can have it plugged in atm

more specs would be nice sp please tell us your systems specs so we can help ya better.