Fill a large pot with lightly-salted water and bring to a rolling boil over high heat. Stir in the kielbasa and return to a boil. Cook until hot, 8 to 10 minutes; drain and cut into bite sized pieces. Place the kielbasa into a slow cooker; stir in the salsa, grape jelly, water, and lemon juice.
Meanwhile, beat the eggs in a mixing bowl; mix in the onion, ground beef, salt, pepper, and crushed cornflakes. Mix with your hands until evenly incorporated. Roll the mixture into balls the size of a large walnut; place into the slow cooker.
Set the slow cooker on High and cook until the meatballs are no longer pink in the center, about 1 hour.