Freezing indicates that there is a lack of calories. Does the freezing already start at the bottle, running up to the vaporizer? In that case the LPG bottle may be wrongly positioned with the dip tube up getting vapor instead of liquid gas to the vaporizer.
If the bottle is OK, it might be a lack of heat coming from the waterflow through the vaporizer regulator, with the engine running you should feel a regulator temperature of at least 50°C (122 F) If the heat is ok, it could be an defective primary stage vale that is leaking, letting past a quantity of liquid gas that is to important for the regulator to cope with. What make of LPG system do you have, Impco?
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