Alright, The verdict is in: No hardware problems. The crossovers in inshot burners had surface corrosion blocking the 2nd burner from catching flame. Lighting from bottom burner by hand at moment of hsi ignition of top burner lit the 3 lower burners and then would confirm flame as per sensor rod. Removed and bead blasted burners. All is fine except she started to short-cycle. Condensate was not comming out of header box fast enough. Daveb 1972 held my hand through all this and was even good enough to call me to help !! He suggested adding a couple degrees pitch to furnace case to help drainage. It is originally a updraft unit so the condensate needed field made drainage. That was all it needed. Corroded crossovers and too little pitch was all that was wrong. No parts needed. Cannot say thank you too all who stayed with me on this. And a shoutout to Dave. All really caused by furnace being in a damp crawlspace.
Thank you guys !!
- kdog likes this