On a new construction house we trying to get the furnaces fired up. I have a 5 jet Concord 80+ LP Gas furnace down stairs and a 3 jet Concord 80+ LP Gas furnace up stairs. Neither will start. They both cycle through prepurge, then lite the glow plug and then only 1 jet ignites then goes out about 2 seconds later. All the jets can be manually lit but go out in 2 seconds. The incoming LP gas has been checked... psi good. The psi out of the mainfold is good (Heice guage). HELP.