I ran into a problem with a H9mpd075 furnace today that has me stumped. The burners ignite inside the burner tubes about .75 inches in front of the orifices, they burn there for about 30 seconds before jumping to the front of the burners where they belong. Furnace is on propane with an inlet pr. of 12 iwc, manifold pr 10 iwc. No adjustment of the manifold pr had any effect (tried from 6 iwc to 11 iwc). Anyone run into this before?