I have a Lennox Pulse (circa'88) and it has this problem. In the AM, when the furnace is started to heat the house, the furnace will try to start for 30 seconds or so. (buzz then stop then buzz then stop) I will listen to this try for 4 complete "buzz / stop" cycles then it stops completely. When i look at it' I'll find a blinking LED on (I think the) ignition control module. When I turn off power to the furnace for 10 seconds and turn it back on again, it usually starts normally.Once the house is warmed, the furnace usually runs normally, untill the next morning. Does anyone have any ideas?