I have an Olson furnace with intermittent pilot light with electronic spark ignition. There is a Honeywell S8610U furnace controller.

When thermostat calls for heat the ignitor sparks and the pilot flame lights. The flame continues to burn while the ignitor continues to spark for about 5+ seconds. Then the ignitor sparks and flame go out. Awhile later the process restarts. The main burners never light and fan does not come on.

Ideas?

If your system uses a flame sensor clean it with steel wool or sand paper.