Hello Grunff, John and Owain:

As promised, here is the solution to my problem, as simple as it may
sound:
According to recommendations, the ignitor tip is supposed to be 5/8"
above the nozzle center (American Standard) and 1/2" (Internet). The
gap between the two tip ends is 1/8". Those dimensions are critical, as
my manual states.
When I called the serviceman today, he went right to
the ignitor and bent the tips down to within 3/8" above the center of
the nozzle. That's all there was to it. Can you imagine my reaction?
Those recommendations in all probability are tailored for clean fuel
oil.
After going through countless trials and tribulations,
one tiny action restored normalty, even without the need of any new
parts.
But, I look at the bright side, it gave me a much better insight into
the workings of my furnace
and will enable me to service it more efficiently.
Thank you again for your assistance and may you have the best of
holidays and a healthy and prosperous New Year.

webster72n.