exhaust fumes from oil furnace

[hvac/airplanes]

I had a customer complaint about smelling oil from furnace during a call for heat but only before fan kicked on. Once fan energizes, the smell went away. I smelt a faint oil smell once I arrive. I'm suspecting possible heat exchanger. This system is a 1994 lowboy front flue. By removing the blower assy. and/or burner assy. will I be able to gain enough access to heat exchanger with a mirror and flashlight to look for cracks? Short of depaneling the furnace and without a borescope, what is the best way to gain access. Also, I had another customer ask if a 90% direct vent gas furnace can be vented through a chimney with sch 40 pvc. I have never seen it done nor have I done it myself. I looked in the code book and I couldn't find where it says you can't. Anyone with an answer I would appreciate it and a possible reference.

[beenthere]

Check that the clean out post's seals are intack.

Yes, you can drop PVC down a chimney to vent a 90%er. But not if the water heater is still vented into the chimney.

[Jim Davis]

When there is an oil smell, there has to be oil sitting somewhere. Many times it is in the air tube from some afterdrip. It can migrate out the air tube and be found on the underside of the burner. Wipe the bottom of the burner and check the inside of the air tube.

[hvac/airplanes]

Thanks for the advice, I will give this a shot and let you know what I find.

[snupytcb]

what furnace is it?

[MicahWes]

Is it definitely unburned fuel that you smell, or partially combusted fuel? A lot of oil furnaces puff out a little when they first light off, especially if the unit doesn't have the best draft when it ignites.