Will the bean salad dressing that I made ahead of time still work? I have been making bean salad for a long time. Recently I mixed together the vinegar, oil, sugar and black pepper for the dressing, and put it in a pint sized canning jar with 2-pc lid and refrigerated it, intending on making in the next day or so, but it never happened.

I still have this nice dressing in the refrigerator, and am wondering about food safety - all the ingredients are fine for long periods unrefrigerated, so there should not be a food safety issue, right? I'm also wondering about staleness. I don't want to use it to make bean salad, and have a less-than-wonderful salad. I hate to throw out perfectly good food. Can anyone help me?
It's fine. Vinaigrettes last pretty much indefinitely in the fridge.

If the oil was exposed to too much light or air it might have become a little rancid. Smelling and tasting it before using it on the salad is a good idea. I wouldn't expect anything like that after just a couple months.

Catija alluded to garlic above. Garlic in oil is dangerous because it has an elevated risk of developing botulism- however in a separated vinaigrette all the particulate matter is submerged in the vinegar portion. More than acidic enough to prevent any botulism.