Steps to Reproduce:
1) Place a rail down and then place a normal minecart on it
2) Enter the minecart
3) Face down, looking at the rail and place a Furnace Minecart and right click with Coal
4) Dismount the minecart and place a few rails down and push both minecarts to easily see that there is smoke coming from the Furnace Minecart but it won't move