Cannot get propane to flow

KZowner49 wrote:
Both tanks were filled at the RV dealership in January. We only used one of them a little and had it topped off at the RV dealership a month ago. The Uhaul place weighed it (40 pounds) and said he didn't think it could take any more propane. I knew it was full. I just took it to the Uhaul place to see the process used to fill the tanks.

Your cylinders may have been overfilled and only allowing liquid to get to the regulator instead of gas.

The 20 lb cylinders are designed to hold 25 lbs of propane. They are not allowed to hold over 20 lbs which is 80% of the cylinders volume. That leaves a volume of gas at the top equal to a out 1.2 gallons. One gallon of liquid propane is equal to about 4.24 lbs.

I have only seen 20 lb cylinders with the tare weight (empty container weight) stamped on the collars that read 17-1/2 to 18-1/2 lbs. That means a full cylinder might weigh between 37-1/2 to 38-1/2 lbs. You stated that your cylinder weighed 40 lbs after it was topped off. You need to check the tare weight of your cylinder to see if the tare weight is 20 lbs. If less than 20 lbs it is over filled. The next step is to loosen the spitter screw on the side of the shut off valve to see if liquid or gas comes out then retighten it. If only gas comes out you should be okay. If liquid comes out you need to take it to a safe place like an open field far away from any open flame and open the screw until gas starts to come out or take it to a propane distributor that has a burner he can connect it to so the excess propane can be safely burned off.

You might not have enough gas volume in the top of the cylinder for gas to flow through the regulator.

Have you tried connecting the cylinders to a BBQ grill or outdoor propane cooker and see if they will work. As others have indicated you could have bad hoses.