a 100lb tank holds about 25 liquid gallons of LP. There is NO WAY to determine the actual amount of Liquid in that tank without weighing the tank. So, If it is filled and holds from 23 to 25 gallons of LP your tank was empty and THAT would be the cause of your problem. I have 2- 100 lb tanks on my outdoor grill and they BOTH will completely drain before the switchover happens. If you have Liquid, it will vaporize. The only thing that may cause a vaporization problem is if the tanks have moisture in them. But, if they are empty, then moisture is not your concern. Doug