'65 Door won't shut without a good, hard slam!

I already know that the problem involves the latch spring. If I disengage it, the latch moves quite easily, but when the spring's in place, the latch is hard to move and thus requires significant force to engage the striker. Is there a way to relax this spring a bit? I'm believe on my '65 it's attached to the latch plate assembly and can't be removed separately.

The other door shuts almost too easily, so I suspect (haven't taken the panel off yet) that the spring has been disengaged on that one.

Thanks,
VR

Thanks, I will keep the spring in place then for now. I'd rather have to slam the door shut than to watch it pop open on the road.