Before doing some gas plumbing I turned off the main gas valve, together with the pilot lights for water heater and furnace. After finishing all the work, I turned gas back on but couldn't start pilot on the pretty old furnace Rheem 3240-80 HD. The low voltage seems to be created. I smell gas when attempting to light the pilot. Does there exist on the internet a repair guide for such an old model? I would like to locate the broken part to replace it or to troubleshoot it somehow. Thanks, h.