I need help with a Trane Model TUC120C960B7 LP Gas Furnace. The furnace is laying on it's left side with the hot surface ignitor at the top and the flame sensor at the bottom. The problem is sometimes on a call for heat the inducer powers up then the hot surface ignitor glows then the gas valve opens and only the top burner ignites the goes off.
I changed the gas valve and converted the valve to LP by changing the valve spring. The inlet LP gas pressure is 12 inches of wc and the outlet pressure is 11 inches of wc.
I also pulled the burners and cleaned them and made sure the crossovers were clean and in line with one another.
I got the burners firing better but they fire from top down to slow and sometimes will not make it all the way down to the flame sensor fast enough before the flame sensor cuts it of.
There is another Trane furnace in the same crawl space same model but 80,000 btu working fine.