I have the dreaded sporadic ignition lockout. I have seen what happens. The first three burners on the right all light off. The fourth one has only a 50/50 chance of lighting. Of course, that is where the flame sensor is. Had a service man in today - and naturally it did not do it for him.
I have pulled out the manifold and checked the orifice for #4 burner - it looks fine, not blocked. In fact, once it manages to light it burns just fine.
(This is a Carrier Weathermaker Infinity high-efficiency job - fuel is LPG).
The manual says that bad flame carryover or propagation of flame between the burners could be the problem.
No kidding.
But they don't say what to do about it.
Thanks any info.