My regular oil burner (hydronic baseboard) cycles on an off every ~10 minutes even after the upstairs has just been warmed up. The combustion fan starts, oil ignites and runs for 2-3 sec's then, pow, the unit shuts down. The baro shakes. Burner is a Reillo, control is a Honeywell with min, max, and diff settings that were not touched from last year.
When I push up the temp on the thermostat upstairs, the circulator kicks in, burner starts and runs happy for several minutes like it should, then shuts down when temp is reached , this suggests it's not a oil supply issue.
What do you think is up?