Intermittent ignition problems.


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Old 01-15-10, 06:25 PM
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Smile Intermittent ignition problems.

Mobilehome, Miller furnace, Beckett Model AF10 series oil burner. I was having problems with air in line and no ignition. I replaced the entire supply line from tank to oil burner in one piece. I still could not get furnace to start at first even though there was no excess air to bleed. I checked the igniter. Opened it and reset furnace and crossed spring terminals with screwdriver and there was no spark. Said Oh well and closed it up and it started and ran for 36 hrs. Came home today and it was down. Tried to bleed, very little air and it would not start. Checked igniter and there was no spark. My brother suggested I start it manually one time. I did and it has been running for about 6 hrs. I think I was dealing with two problems. The supply line I fixed but I don't know what my ignition problem is. Any help will be appreciated. Thank you.
 
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Old 01-15-10, 07:15 PM
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Miller w/Beckett

I suspect you have a weak igniton transformer. Other causes could be a fouled nozzle or worn/maladjusted electrodes.
 
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Old 01-15-10, 07:46 PM
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Question

Thanks for the feedback. The furnace is 2 years old. I changed the nozzle this year and the diodeselectrodes are in great shape and adjusted properly. How do I check the ignition transformer. Thanks
 

Last edited by hunt7777; 01-15-10 at 07:48 PM. Reason: part description
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Old 01-15-10, 08:13 PM
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Ignitor

With the furnace being only 2 years old, you would have an electronic ignitor. With the power shut off, measure from each spring to ground (such as a burner mounting bolt). The reading should be less than 2,000 ohms. If there is more than a 20% difference in the readings, the ignitior needs to be replaced.

Another way is dangerous & must be done with great care.
Remove the cad cell eye. (If the eye sees light it shuts off the ignitor.)
Disconnect the 3/16" nozzle line & direct it into a container.
Start the burner & use a WELL insulated screwdriver (no wooden handles, plastic only) to jump across the springs. Maintain contact with one spring while drawing the screwdriver blade away from the other spring. The arc should be blue, at least 3/4" long, & have a sharp crack sound.
 
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Old 01-17-10, 07:39 AM
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Thanks for the suggestions Grady. I'm just getting back to the furnace after being away for a day. In the meantime the furnace ran almost 24 hrs and then shut down again. So I tried bleeding it. There was some air (not much). Question? Why is there any air. I have one continious piece of supply line with just one flair fitting at the burner. Where is the air coming from? ....And the burner did not ignite. I tried a second time with no success.
So I did once again what I do not like to do and I manually ignited the furnace by pushing a little piece of kerosene paper into the chamber and reset. It started right away and has been runningfor the past eighteen hrs. Question? Why will the furnace constantly go to temp by igniting time after time using the electronic ignition and then shut down and then fail to lite? Why will the ignition work but not work? I am going to check the igniter as you suggested but I have to get the tester from my brother when I see him today.
 

Last edited by hunt7777; 01-17-10 at 07:40 AM. Reason: spelled word incorrectly
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Old 01-17-10, 08:45 AM
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Air/Ignition

I really wonder if you are getting air. As a test, the next time it locks out don't open the bleeder until you confirm air. This can be done by disconnecting the 3/16" nozzle line & directing it into a container. If you don't get fuel thru a safety cycle when you reset the control, you do have air. Making a good, air tight, flare is not as easy as one would think. It takes practice. This video is a classic "how not to flare tubing":
Copper Tubing Flaring Tool Video
This, while not a video, is the ONLY thing I've found on the web which mentions preparation of the end of the tubing before flaring. Copper.org: Applications: Tube, Pipe & Fittings: Copper Tube Handbook: VIII. Flared Joints
Also make sure there is no debris on the cone of the tool & you coat it with a drop or two of oil before flaring (even cooking oil is better than nothing).

Ignition transformers can be intermittent but the slightest fleck of 'junk' in a nozzle can exibit the same symptoms.
 
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Old 01-17-10, 09:29 AM
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Thanks for the quick response and the additional information. Your helping me to to better understand my problem and how to proceed to resolve it and I appreciate your efforts. I previously had an old Miller furnace and I did not have these kinds of problems. I could run out of Kero, fill up, bleed the furnace and it woul run all winter. Service it once a year and it was good. Hope you don't mind all the questions but it's my way of thoroughly understanding the problem. By the way Question: If there is a small piece of debri in the nozzle, would it not consistently cause a problem? The thing that puzzles me most about a problem such as this is that the furnace will go to temp and shut down and ignite again over and over and then shut down and will not ignite. (Just shoot me.)LOL...Thanks again and I will update you ASAP.
 
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Old 01-17-10, 10:20 AM
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Nozzle junk

Because of the way oil swirls in a nozzle a fleck of debris can cause erratic spray patterns. Before I install a new nozzle I flush the assembly with carburetor cleaner, then attach the assembly to the nozzle line & run a cycle of fuel thru it, then install the nozzle. The smaller the nozzle, the more critical "clean" is. In applications where a .50gph nozzle is used, I always suggest a 10 micron spin on fuel filter.

After 20+ years in the trade, intermittent problems still make me crazy. It's awfully hard to fix something which isn't broke when I get there.
 
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Old 01-17-10, 11:19 AM
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Thanks again. I see youe experienced on this site also. I was looking fora way to express my frustration. That icon at the end of your text was so funny it made me laugh out loud. I'll let you know what happens.
 
 

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