The wheel I have (on loan, second hand, well used) is a Logitech Wingman Formula Force GP.
I've had the very same as my first wheel and I loved it!
The downside is that pots started going out after a bit more than a year and there simply weren't spares to buy.
Force feedback is VERY strong and actually very good, gives you good feeling of the track and the car, so you must be doing something wrong there. When you calibrate it through Logitech Profiler it should give you the option to test it, did you try that and did you have FF then?
If not, check first if the cable from electric supply is connected well. Then see if the electric supply actually works.
Also, you should put the wheel turn to 180 degrees as it is its original limit. In LFS, look under "controls" section and see if FF is enabled and for how strong. It shouldn't be more than 40-50% if I remember well, because it does have strong FF.