Why is my GPU fan weak?

I got ati hd 5670 that requires a 6 pin PCI e (extra power) but my PSU doesn't have one and there is no free 6 pin to molex in my GPU.. anyways... My psu is powerlogic atx 550 watts that doesn't have a 6 pin that means if a PSU doesn't have a 6 pin PCI E it means its a weak PSU to run the GPU that requires one.

I bought my PSU 2006 LOL  D

I created a 6 pin I mean I buy a 6 copper wire and put it to the molex (Long story) But it WORKS!!
Before If I din't put a connector to the molex it does not start and no monitor picture but when I came up with this idea it works fine except for the gpu fan.

NOW!! about the GPU fan.. It still works.. But when I manually set the Fan to 20% it turns off (what I mean by turn off is the GPU fan stops spinning but it still spin in a very slow RPM maybe the snail is faster though) and My 100% manual fan is like 70% only..

So My REAL QUESTION IS THIS ONE:
What's the problem? Is it the Whole GPU OR MY PSU?

Thanks!!!