It depends on which ranger, which generation, and what part of the series they are in.
Usually I'd say not much however certain points in the series have shown them to be 10 times more powerful in the suits. Most of the power rangers' ability are based on skill and weapons though, I mean if you had a fair fight Zedd and Goldar would in their own right decimate any generation of power rangers after the first one, unlike rangers who are subjected to age beings like Zedd and Goldar aren't even human, so things apply differently for them, just look at Rita being over 10,000 years old and still stronger than ever.
The rangers aren't all that tough considering they rely mostly on weapons and zords to fight their battles, without those zords and weapons they'd be screwed from the start. ---
In SPD one of the rangers reasonably easily picked up a car.