Ah, "Slow Ignition" is covered -, summarising;It’ll be covered by something like “burner fails to light”. What you have is delayed ignition.
Yep, there could be lots of factors. Many more than what’s listed in the manual. If for example the head/electrode settings are on the edge of ok with a cold flue and you don’t have any ventilation you could end up with something silly like only lighting smoothly when hot if the kitchen extractor is on!Ah, "Slow Ignition" is covered -, summarising;
>check oil pressure/ nozzle/ filter
>electrode adjustment and HT system
>bad/wrong fuel.
Hot/cold starts are not mentioned but I'm sure that is a factor and could be a central one here. The more I listen the more I sure there is a big variation in ignition delay, but not yet got a good correlation with anything much.