Turn crockpot onto low, and cut ribs into 6 servings.
Prepare a large skillet by coating it with cooking spray. Place ribs in the skillet over high heat and brown all sides.
Peel potatoes and carrots. Cut them into thirds, then halves. Place half of potatoes and carrots in the bottom of the crockpot.
Place the spare ribs on top in a single layer if possible. Cover with the remaining carrots and potatoes.
In a blender, combine onion, lemon juice, vinegar, Worcestershire sauce, brown sugar, and chili sauce.
Blend on high until all ingredients are mixed well. Evenly distribute the sauce over the carrots and potatoes.
Cook on low for 8-10 hours, or low for 6-7 hours then turn to high for an additional 1 1/2 hours, stirring occasionally.