I have a Day and Night Furnace Model 394JAW036065 with electric ignition. The pilot sometimes does not turn on. I can see the igniter sparking. But sometimes the pilot comes on ~3 to 4 minutes after the igniter starts sparking. Once the pilot comes on, everything is working fine and subsequent on off cycles the pilot comes on as soon as igniter is on. Looks like the problem is only on a cold start. The wall thermostat is programed to turn the furnace ON during the Morning and Evening. The problem occurs during the first start of the Furnace in the Morning and Evening. What could be the cause of this problem. Is it the ignition the Pilot or the gas control valve?

The most common cause of problems like this is a dirty pilot orifice.