I have a recurring problem with Coal Generators where they randomly stop requesting fuel and incorrectly report "Insufficient Resources - Coal" even though there is plenty of coal available. When this happens I have to restart the game and deconstruct/re-construct the generator to temporarily fix the problem. This is really frustrating. Effects both auto-sweeper and manual delivery.
Build and operate coal generators. I always use automation to try to limit wasted resources. I'm not sure what causes the coal generators to get stuck like this.