I have a older HEIL furnace with the ignitor and pilot light. Thing is, lately when the furnace turns on, you can hear the ignitor going, you can see spark, but the pilot won't light. If I stick a match in there the pilot then lights up and the furnace works normal until it shuts off.
Any ideas why the spark wouldn't be lighting the pilot?
Usually that is the spark not going through the pilot gas path to ignite it.
First check if some rust or scale is not in the pilot cobra head, diverting the pilot gas away from the ignition spark. Often tapping the base of the pilot assy where it is attached to the furnace with a screwdriver when the furnace is trying to ignite the pilot gas will do it.. You are using the tapping vibration and pilot gas pressure to dislodge any debris.
If it is clear...
A small judicious repositioning of the igniter tip to move the spark through the pilot gas is the answer.