Peter Wells wrote:

It seems the pilot in our gas furnace doesn't reliably ignite the main
burner. The upshot is that sometimes, say 1 in 4, the furnace will start
with a real boom. The furnace is regularly serviced and works fine apart
from the starting issue, I explain the problem to the tech's and they take
the burner out, look at it but don't seem to fix it. Any suggestions.

Thanks,

Peter

My furnace did that after I cleaned it. Boom sometimes blew the furnace
door off. Got my attention immediately!

A metal channel that collected a bit of gas from each burner and led it to
the pilot was installed wrong (reversed end for end). If your problem
began after somebody was into it, you might have a similar problem.

In any case, it needs fixen'.

Roby