You can smell my oil furnace suddenly!? :(

tipoftheislandgirlJanuary 30, 2007

This is the first time I have lived in a place that you can not tell I have an oil furnace for heat.

ALMOST every time my furnace has turned for the last 3 weeks, you can smell the burnt oil smell when the blower kicks in. We had started reno's in the house and we were turning off the digital thermostat during the day. At this time, we had noticed the furnace still kicking in at times. My husband then started turning off the emergency shut off and turning it back on at night. Guess what? After this the smell started!!! It doesn't always smell though??? I have tried multiple ways to shut down the house like: turn thermostat down first below room temp, letting the furnace completely turn itself off and then flicking the switch and then making sure that when I turned it back on the thermostat was turned down lower that room temp. so that if the furnace was flooding itself it didn't have a chance too. The smell is becoming more frequent.

As a migraine sufferer, this smell will trigger a migraine for me! :(

Please tell me whether we are creating this problem by using the emergency shutoff or if our furnace needs some TLC to make it all better. :D

Thank you kindly for your help.


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Uh oh...can one crack a heat exchanger by not letting it cool down ?

    Bookmark   January 30, 2007 at 5:08PM
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So, That's nice. What are you smelling ? Raw oil or the
products of combustion ? There is a world of difference
in the two. Do you know the difference ? It would help.
If you can smell " oil " in any oil furnace there is a problem. If set up properly with no leaks. They DON'T smell.

    Bookmark   January 30, 2007 at 6:22PM
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likely that you have let the chimney cool signifigantly by extending the furnace off-time. this reduces draft, which causes the exhaust gasses not to be completely sucked up the flue when the furnace is turned on, thus the smell. this is my theory.

stop playing with it! set the thermostat and let it run normally for a day or two, see if this solves the problem, if not, call a tech.

    Bookmark   January 30, 2007 at 6:35PM
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I have turned off my boiler every single night for the last 30 years before the last two showers and turned it back on in the morning. I have never had an oil smell or an equipment failure.

You might have an oil leak somewhere or a crack in the heat exchanger depending upon when you smell the odor.

    Bookmark   January 30, 2007 at 9:23PM
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berlin, your theory is way off, with the amount of air a modern burner uses for combustion the chimney would have to be about 600 feet tall, on a minus 50 degree day with about a 150 mph wind blowing across the top to create a down draft that would effect the burner operation.
tipoftheislandgirl, shutting off the furnace at the t-stat, emergency switch or anyplace is not going to make the smell go away. Somebody mentioned a cracked heat exchanger, thats an educated possibility and describing smells is very difficult. As kalining states, there is a difference depending on what exactly your smelling. The best advice anyone here can give someone who is getting strange odors coming out of their oil fired furnace is to have a professional come and take a look "pronto"! More then likely that furnace has not been cleaned and PM'd in a long time.

    Bookmark   January 30, 2007 at 9:28PM
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Your chimney can't be 600 feet tall if it's in Philly. You can't go higher than Ben Franklin.

    Bookmark   January 30, 2007 at 10:06PM
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That was an exagerated example to explain a point Mr. baymee sir. ;-)

    Bookmark   January 30, 2007 at 10:35PM
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"berlin, your theory is way off, with the amount of air a modern burner uses for combustion the chimney would have to be about 600 feet tall, on a minus 50 degree day with about a 150 mph wind blowing across the top to create a down draft that would effect the burner operation"

you completely misunderstood my point. anyone who thinks oil exhaust never has a smell hasn't stuck their head near a chimney when a furnace is starting up etc. properly tuned, an oil burner will produce little to no oder while in operation, however upon cold startup and in some cases shut-down, an oil burner will produce a noticable and strong oder, however, this is not an issue if the furnace is venting properly.

now, whether it's a downdraft or just a poor draft from an exterior chimney, i have seen on certain setups, when not having been run for a long time, on a poor chimney, the oil exhaust will feed, for a few moments, out of a stuck baro or poorly sealing vent pipe. this has NOTHING to do with anything interfering with the burner. point is, i've seen it happen and it will leave a lingering oder in the home. period. having said that, whether this is their particular issue or not, i don't know, but it's worth a try. yes, baymee, most chimneys draft fine cold, hot, or otherwise, but some don't; they need the periodic warmth of flue gasses to keep them drafting well or at all.

    Bookmark   January 30, 2007 at 11:44PM
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The smell is like burnt oil. My husband says to tell you that there are no leaks from the tank to the furnace. We have had some high winds come through, will a blown off chimney cap make this smell now?

    Bookmark   January 31, 2007 at 12:28AM
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The smell is always stronger at the vents than by the furnace itself. and only when the blower turns on not when initial start up.

    Bookmark   January 31, 2007 at 12:34AM
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It sounds more like a crack in the heat exchanger and that would require that the furnace be replaced asap!

    Bookmark   January 31, 2007 at 5:50AM
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The carbon monoxide detector started chirping when my heat exchanger went. If you have not one already CO (carbon monoxide) detector, GET SOME. Mount one a wall over a vent. Put the other near the furnace. Be could take 20 minutes to sound an alarm. If it starts chirping, you've a CO problem; shut off your furnace. If it makes that god-awful BRAAAP! sound, you've a life-threatening CO problem. Shut off the furnace and open your windows...and leave the house for a while.

This is only a non-pro's (second) guess...yet I briefly had a similar problem with my new oil furnace. When I fitted the flue pipe to the back of my Crown lowboy, I pushed it too far. The flue collar was loose, so this allowed the pipe to push behind it (mistake #1). I hadn't yet clamped the flue to the outlet (mistake #2). So when I test-fired the furnace some flue exhaust was getting sucked into the return. It was not an overpowering smell; It failed to trip the CO detectors. However it was a real problem caused by errors on my part.

Is it possible your husband made similar mistakes? Could he have given the furnace a good whack, shifting flue pipes that were not tightened? Did he make some sort of change to the furnace that seemed inconsequential at the time? A cracked heat exchanger means a new furnace. You want to first rule out other problems, if you can.

Good luck.


BTW...I always shut off my furnace by the thermostat switch. This allows the fan to run until the heat exchanger has cooled.

    Bookmark   January 31, 2007 at 9:22AM
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Oil doesn't product much CO and the detectors may never sound for a crack.

    Bookmark   January 31, 2007 at 11:18AM
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Oil furnaces don't crack as often as gas furnaces, the heat exchangers seem to be a little more well made.

    Bookmark   January 31, 2007 at 11:59AM
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Thanks for that, Baymee. That makes a lot of sense. A four-inch crack in my old Magic Chef only caused the detectors to chirp. Even so, it didn't smell too healthy. I found some soot in the old supply plenum and some of the ducts when I replaced the system. It might have stained the walls above the registers had I kept on going.


You can have a pro check your heat exchanger with a "smoke bomb".



    Bookmark   January 31, 2007 at 12:19PM
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Thank you for all your help. :) We are going to start with a filter change and then replace the Spray jets. A d.i.y. tune up. lol My husband was talking about cleaning up the electrodes to the furnace at the same time. Is their anything else we can do to tune it up brfore we call in a specialist. We are trying to keep cost down. We want to install a woodstove instead. But our budgets not quite there yet. haha murphy's law.

    Bookmark   January 31, 2007 at 2:54PM
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Oil at least gives you a warning that you are leaking CO into the air supply. You smell the odors and are warned. Gas heat gives no warning without the detector.

    Bookmark   January 31, 2007 at 5:09PM
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tipoftheislandgirl,when was the last time this furnace had a good brushing and vacuum? Partially plugged flue passages and baffles will also give similar symptoms like what you're describing. Cleaning that section of the furnace involves removing the burner and depending on the particular brand furnace you may even have to remove the plate the burner mounts to. And I could almost guarantee snapping a few mounting studs trying to unbolt the plate. Take a look inside of the barometric, (that damper looking thing in a tee in the flue pipe) and see if there is a pretty good build up of soot. If so you're partially plugged.

    Bookmark   January 31, 2007 at 8:39PM
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take some pics of your furnace, and venting setup, perhaps even the primary heat exhanger and oil burner if you can and post them. this could help potentially diagnose a problem.

    Bookmark   February 1, 2007 at 12:17AM
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woke up and my wife told me she smelled a strong oil smell and shut off the furnace. i'm so groggy and out of it in the morning i have no idea. she told me to "check it out", whatever that means. I go look at it. It's a furnace allright. half a tank of oil. i call emergency service and tell them and they tell me 6 hours. i noted some soot on the outside, but these things are so filthy that who knows when it got there and how long it's been there. my theory was it sooted up because that's what happened last time we had oil smell (turned out the cause then was the wrong size nozzle installed).

It's been very cold here lately due to an arctic snow blast. single digits a few nites. teens in the days. well, today when the oil smell happened, it was a balmy 31 when we woke up. turning the furnace off all day waiting for the guy to show wasn't a big deal. strategically placed electric heaters and a roaring fire in the fireplace ensured that it never really got cold.

he took the guts of the furnace apart and it all looked good. no significant soot or anything. he suggested that it could be a cracked heat exchanger but didn't check it per se. after he got the furnace back together he said there was one more thing he wanted to check. he started examining the run of pipe to the exhaust stack and discovered a 2-3 inch gap. i recalled a dead bird i found in the sealed off furnace room a month or so ago. couldn't figure out how it got in there and threw it in the trash. well i guess we know now.

so he squished the pipes back together and secured with a sheet metal screw. no more gap.

i have no idea if this fixed the problem. it may make sense. i've felt like $#!+ all day with a sore throat.. my wife complains that it's worse when she goes upstairs.

i have a few windows open, downstairs and up. With a huge roaring fire trying to suck everything out through the chimney.

oh and i ran out and bought a second CO detector, just in case the one i have is broken.

i just hope it fixes the problem. if it doesn't, do i just keep calling techs back until i find someone who can figure it out? how do you check a heat exchanger? (all he said was it was hard to see into my unit 'cos it's so small)

is there a reason why we haven't noticed "oil smell" until the first normal temperature day following an unprecedented coldspell?

i'm a couple hours from easton, pa, how much does our forum moderator charge? ;)

    Bookmark   January 18, 2009 at 9:25PM
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NOZZLE: You need to replace the oil nozzle with the correct size according to the rating plate (sticker) on the side of the furnace.

ELECTRODES: Then you need to set up the electrode gap to no more than 1/8 inch apart, which will ensure a good spark upon ignition. The electrodes must be cleaned of any carbon build-up. The electrodes must also be set 1/16 inch past the end of the nozzle, ensuring it does not touch the nose cone, and spark becomes hindered.

AIR: The most critical step now is setting the ratio of air to fuel input. The fuel is generally set to 100 psi on older oil furnaces and higher on newer ones. DO NOT MESS WITH AN OIL PUMP THAT HAS ALREADY BEEN SET UP TO WORK CORRECTLY! Only adjust the air input if you know what you are doing. Otherwise you may start a house fire.

Set the air by:
[A]using a smoke gauge to measure the amount of carbon in the smoke by putting a test hole into the vent 2/3 distance from furnace to draft regulator. Your successful reading will be 0 to 1, referring to an approved smoke scale. If there is too much air to fuel ratio, smoke will most certainly pour into your home and will smell like oil.
[B]set the draft in the chimney with an approved gauge. The results will vary depending on your oil pressure & air volume into the burner, by the the height & diameter of your chimney, by the temperature outside of your home. Setting this up in Winter is vastly different than Summer because the temperature rise is different. You want results to read -.03" wc to -.06" wc (water column). This essentially means that you have a vacuum at the top of your chimney sucking smoke out, so even if small openings exist in your venting, it is a negative pressure.

Licensed oil burner technician offering free advise.

    Bookmark   August 22, 2010 at 1:12PM
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We have a 1995 mobile home that has the oil tank outside and over the years we have had problems with the heating system. Forced hot air oil fired. We put a 5 gallon bucket on the oil tank fuel gauge to keep the snow off of the gauge and tank vent.

Over the years here in Maine we have gotten some serious snow. 2 ft overnight is not out of the ordinary. More like the norm. anyway one year we got 3 ft overnight and the furnace would not start, tripped the motor breaker. I checked the oil level, we had plenty. Looked in the little door over the motor when the furnace was trying to start and it was not burning, until I opened that little door.

Trailers, mobile homes, double wide have a fresh air intake in the same tube the exhaust goes out. Well not really it is a double walled stack and one it for exhaust and one is for intake/fresh air.

Now the snow on the roof got so deep you could not see the chimney at all. So the fresh air intake was plugged and the furnace would not fire. We smelled oil, kero actually when the furnace tried to start.

Now this year we had a 1� snow storm but it covered the oil tanks vent on the top. I ran into the same problem as I did when the roof vent was plugged. So I cleaned off the oil tank top and now she is fine. No smell, burns great.

Just a heads up to those who have a similar problem. Check all your vents, air intakes on your furnace and oil tank.


    Bookmark   December 28, 2010 at 10:48AM
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Our boiler has started to play up this last couple of months we have burned 500 litres of oil under 2months ,The boiler pours smoke out really bad also the smell of oil is really bad ,and our neghibours have complained to us about the smell as it even smells in there house ,
The boiler will go for about a hour and trips out so we have to reset it every time it can take up to half a hour to get it going ,when we finally get it to go the smoke pours out it any idea what could cause this

    Bookmark   February 25, 2011 at 4:19PM
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