In December 2023 I noticed lottsa smoke coming from my furnace. I live in florida, so dont use it too much. I did a smoke test and draft check january 2023 and all was good.

It was still heating house fine.

Many years ago I started doing my own maintenance/tune ups because I could not find anyone in florida to do it right. Even the guy who installed it didnt set it up properly. So, I check smoke and draft at least once a year. I change filter at every take fill. Strainer, nozzle and electrodes (yes I adj them too) every year or two. There are a few other parts that Ive changed as called for in the maintenance manual, that I cant remember right now. I also got the proper specs from the manufactures. One service guy actually came with a later revised spec for a later model and some specs were different. I confirmed with the manufacturer that those specs were wrong for my model year. He also didnt check draft. I can post that letter.

Anyway Im having doubts about my tuning ability, so I again looked for someone qualified. I contacted over 70 HVAC service companies in my and neighboring counties in the past two weeks. I found no one. Many said they could, but when asked how they adj co or stack temp, then didnt know.

Last week I scrubbed out then chamber, heat exchangers, sight tubes, flue, and chimney. Whatta mess! Then I changed the nozzle which was less then 2 years old (it was dripping oil and Ive never seen that before) and even though it looked fine, I changed the pump strainer too.

Im going to order a pressure gauge to hook up permanently to the pump, to check and monitor the pressure which Ive never checked. Suggestions for a good accurate brand?

Any ideas why it was smoking so much?

tks, paul

  • 2
    Smoking should be a sign of rich burning, too much oil for the amount of air. Soot should have the same reason. Either your nozzle is too large or your oil pump/injection pump is set too high and not stopping oil flow.
    – crip659
    Commented Jan 6 at 19:20
  • 2
    If the nozzle is dripping, an oil pool in the burner is not good either.
    – crip659
    Commented Jan 6 at 19:58

1 Answer 1


A comment above mentions too-high oil pressure as a possible cause, but too-low pressure can cause a smokey flame as well. If the gear pump is severely worn, it will fail to develop enough pressure to properly atomize the fuel oil info fine droplets that burn easily and completely. You may get droplets too large, or worse, a stream instead of a fine fog of fuel oil.

In addition, a severely worn gear pump when not running will allow fuel oil to pass through to the nozzle if the nozzle is lower than the fuel level in the tank. You said the nozzle was dripping, so this could be the cause.

I think a permanent pressure gauge on the high pressure fuel line is a great idea, and should help you solve the smoke problem.

  • As soon as i choose a pressure gauge ill ck pressure and shut off.
    – Paul Mars
    Commented Jan 8 at 19:13
  • Because of clearance issues ill need a 4' tube between the pressure guage and pump. How do i get the air out of that?
    – Paul Mars
    Commented Jan 9 at 22:34
  • @PaulMars Air in the line won't change the pressure reading, but it could cause the flame to sputter on startup and shutdown due to the air in tubing being being a pressure reservoir. To remove air, install the gauge, start up the burner, then very slightly loosen the connection at the gauge. Air will be expelled. As soon as fuel oil starts leaking from the connection, tighten it. Protect your eyes. Best to cover the connection with a cloth to catch any spray and look for a wet spot. Remember, slightly loosen the connection so you don't make a mess.
    – MTA
    Commented Jan 9 at 23:25
  • Thanks 8 more to go...it says. Maybe now it will let me post
    – Paul Mars
    Commented Jan 11 at 1:06
  • Juck checked pressure and shut off. Running pressure was proper at 100 lbs Pump papers say "after shutdown it should be 80% or higher. NOTE: A and B model pumps could theoretically have a cut-off pressure of less than 80%. The important operation is that it drops to some value and stops." ​im type A pump (a2va-7116) ​how long should it stop? ​Mine dropped immediately to 63, then after 5 minutes on a timer it was 43, then after another 5 minutes it was at 40. Then i removed gauge.
    – Paul Mars
    Commented Jan 12 at 17:17

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