Suburban NT-12SE furnace - gas and spark, but no fire - why?

Ok, I repositioned the electrode gap – it is now 1/8" between the electrodes and 3/16" between the electrodes and the burner. The gap is directly over the burner opening. I turned it on and for a brief second I did see flame in the burner but it went right out. I tried several more times afterwards but no fire. ??? Sigh.

We'll build a manometer later tomorrow.

Dave