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TomGood Member Posts: 3
I do commercial refrigeration, but a friend of mine asked me to look at his furnace last week. It would lite , flicker a little then go out.
he had already changed the nozzle. And there was no air in fuel, flue and chimney all clear. 
I guessed probably a bad pump, so I made up a pump pressure tester and the pump was fine. I pulled out the nozzle assembly and adjust the electrodes slightly , checked the blast tube and retention head. Put it back together. If I raised the pressure to 110 psi it would run fine , but would not run at 100 psi. 
He had fuel delivered about 2 days before that , so I thought maybe poor fuel quality. 
It is a trailer with an outside tank, but ambient temp was about 40F. 🤷🏼‍♂️


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,378
    edited December 2021
    Tell your friend to call a competent oil burner tech, and/or the company that provides him heating oil.
    I'm an oil burner tech. I'm not going to my friend's place to work on his commercial refrigeration.
    Nozzle/pump pressure change requires full combustion testing when finished.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,753
    There is a problem with the air fuel mixture. The nozzle could be partially plugged, the air adjustment could be off, there could be a build up of dirt on the combustion air fan, there could be a partial blockage in the fuel system, the pump strainer may be clogged, the vet may be blocked, the flame sensor eye could be defective, the flame sensor eye could be dirty, the motor may be failing, the pump coupling may be failing, the fuel line from the tank may have a kink in it, are there any blades missing on the combustion fan?, Is the Finickin pin out of alignment?, are all the Kronston valves open? have you checked the headlight fluid? are muffler bearings worn out? Did you check the superheat with a digital thermometer? were the ailerons in line? were the flaps set for the proper vector? were there any resistors on the flux capacitor relays? Did you have sufficient RAM for the megabits of carbon monoxide in the exhaust inlet retention facilitator?

    Are you sure you want to play with FIRE in your friends home?

    If it is the muffler bearings here is a DIY to watch

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • TomGood
    TomGood Member Posts: 3
    edited December 2021
    I figured I’d get comments like this. Lol 
    he did have a heating company look at it after I was there. I just went to get him heat until they could make it out. They changed the nozzle and air filter and left the pump pressure where I set it. 
    He says it’s working fine , but I like to know why , not just make it work. They charged him $$$. And didn’t really solve the problem and left my band-aid solution in place. 
    I recommended he get a different company to check it out, but he says it’s working fine and he can’t afford to keep having people look at it. 
    The pump pressure stays right where I put it , it’s not a kinked line or plugged screen or air or muffler bearing. Lol. 
  • MaxMercy
    MaxMercy Member Posts: 456
    edited December 2021
    TomGood said:

    They charged him $xxx. And didn’t really solve the problem and left my band-aid solution in place.

    You'll have to redact the price you quoted - verboten on this site.

    They might have repaired it even if they left the pressure where you set it. The nozzle's gph rating is generally determined at 100 lbs, but you can find charts on line that will show you the same nozzle's flow at different pressures. A lot of new burners are shipped with higher pressures pre-set for better atomization.

    The price you quoted isn't that high, so they likely didn't replace anything other than typical maintenance items: filter, screen, nozzle, points (if worn), and hopefully adjusted combustion to match the nozzle's flow at 110 lbs.

    More than likely, it would now run correctly if the pump pressure was set back to 100lbs (with the combustion air set to match).
    EBEBRATT-Ed Member Posts: 14,543

    Sometimes a weak pump will sometimes deliver oil at a lower pressure and if you raise the pressure and it quits it's a bad pump. Doesn't sound like the pump is bad.

    Raising the pressure delivered more oil to the nozzle and then it ran which doesn't really make sense unless the burner had way to much air adjustment but that is doubtful
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,378
    The main problem is you didn't perform a complete combustion test (and also you didn't really diagnose the problem). You may have left the burner in a worse state, even unsafe. If that burner soots up the house, or worse, you were the last person to touch it-from there you'll get to find out how good of friends you are if something bad happens.
    No one knows if the burner is working 'fine'.
    Kudos for getting him out of a jamb. He should take your advice and get some local recommendation for a competent oil burner tech. He's going to need one again, maybe soon, but Murphy's Law predicts it will happen when it's very cold, or a snow storm, and then he'll be SOL.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,753
    edited December 2021
    This sounds like a mobile home or manufactured housing furnace like a Nordyne or Coleman. These furnaces are difficult to put a combustion test on them. They are designed with a front door that seals the burner compartment from the living space because the blower inlet is the front door of the furnace. That usually puts the exhaust vent in the same air space zone as the blower inlet. They get away with that by making the exhaust vent a sealed unit from the exhaust outlet straight thru the roof of the home. No elbows or seems in the pipe. Putting a hole to take a combustion test in the vent pipe will cause exhaust gasses to leak out into the blower compartment and be distributed thru the home.

    I rarely did combustion tests on those old Miller Furnaces. When there was a problem, and I thought it prudent to check the Smoke, and CO2, I would use high temperature RTV red silicone to seal a 1/4" bolt in the sampling hole. Draft over fire was doable but you could not check draft at the breach. The blower comes on and screws up the air pressures in the place you are taking the test.

    This is one that you just had to get to know how they worked and set the burner buy the color of the flame. I know that many of you are going to say that I'm wrong to do it that way, but unless you work on a lot of manufactured housing oil furnaces, you don't really understand the way they work. But an inexperienced oil burner tech would need to do the testing and carry plenty of 1/4" bolts and a tube of red silicone until they get the hang of it. Get to see what the flame looks like at 11% CO2 and zero smoke.

    When I moved from Philadelphia to South Jersey I could not believe how these furnaces were legal, not having a ducted return into the living space. After researching the concept and design, I understood how they worked. I must have worked on over 200 Mobile Home Furnaces in my years in South Jersey. There are lots of Trailer parks there, Not so many in Philadelphia.

    You learn on what equipment is in your area of operation. Trailer parks = mobile home furnaces. It also = lower income consumers and more DIY failures.

    It sounds like there was a service tech there after @TomGood looked at it. If he is experienced on MH furnaces, then you are probably fine. If he does not work on a lot of MH furnaces then your friend should ask his oil dealer for help or a recommendation on a good burner mechanic. His furnace should get maintenance every year to include the oil filter cartridge and nozzle replacement along with cleaning the burner fan, combustion head, and electrodes. Some of the older motors have oil cups and the electrodes need to be properly set for smooth ignition. The air gate adjustment should be done by an experienced MH burner tech or the rookie should do the combustion test and properly seal the test port with a high temp sealer. Air filter on the blower door should be cleaned by the homeowner several times a season.

    And finally, don't use automotive muffler bearings on Oil Furnace Exhaust pipes. You must use the ones designed for Furnaces.

    I hope this is helpful.

    Mr. Ed
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    rick in Alaska
  • TomGood
    TomGood Member Posts: 3
    Very educational Mr. Ed. 
    It’s been bothering me , why I had to raise the fuel pressure from 100 to 110 to make it run right. 
    The experts that came and looked at it didn’t think that was a big deal and left it that way. 
    I will figure this out. I’ve been doing commercial refrigeration since 1995. Mostly self taught. Things bother me. 
    EBEBRATT-Ed Member Posts: 14,543
    Never liked that mobile home stuff, very touchy.

    I had a bad experience with a Miller oil fired furnace a brand new replacement. The homeowner kept complaining about smelling fumes which was the same problem they had with their old furnace. I thought she was nuts. She wasn't.

    We finally pulled that new furnace back out and stripped it down and found a small hole in the hx where Miller had missed a weld. I don't remember if they got us a new hx or a new furnace but that fixed it

    Left a bad taste in my mouth for anything Miller

    The last one I looked at was Miller gas fired for a distant relative who guess what....complained of smells.

    With the door open to the furnace I held some plastic wrap over the combustion opening over the fire and started and stopped the indoor blower several times (burner off) and the plastic wrap moved. That was good enough for me.

    She didn't like my price and got someone else to replace it.

    I was thrilled