Ignition problems

[ageingrodder]

I have a DIY waste oil burning furnace using a siphon nozzle in a ckBurners heater block in a Beckett burner.  I have been using this setup for about six seasons with minimal problems but recently it has been having problems igniting.  The burner motor start and after about 3-4 seconds it will ignite but immediately go out, then quickly reignite, then go out again, then reignite.  It varies, but sometimes it will do this about five times before it settles into a steady burn.  The PID says it is reaching the proper preheat temperature.  Your thoughts and suggestions?

[Russ]

I would have to think it is either a spark or fuel problem.  I have in the past disconnected the air supply and watched the spark because my electrodes were grounding out to the retention head.  That would give you an idea if it is a spark problem.

Have you cleaned the nozzle lately?

[ageingrodder]

Yes, I checked the nozzle and fuel system.  I'd lean more towards spark because at times after it ignites and starts to burn, the furnace rumbles for a short time indicating what I believe to be too much accumulated oil.  Why would it fire then go out?  Wouldn't it continue to burn without additional spark after initial ignition?

Thanks for your response.

[Joe mamma]

Sounds like a safety feature such as a bad thermopile.

[Russ]

From what I have read, waste oil needs a continuous spark.  Because of impurities in the oil (water, antifreeze, etc...) there may not always be a continuous fire and could cause the fire to go out.

I have had ignitors go out, but usually they quit all together.  Some primarys are meant to be intermittent, so the ignitor doesnt have to run continuously, but if your furnace never did this in the past, I would doubt you have one of those.

Could the electrodes be shorting out somewhere? 

[ShopSpecialties]

Waste oil does not need continuous spark. The latest primary controls on commercial waste oil heaters actually turn off the ignitor when cad cell sees flame.

Sounds like you are sucking air.

[ageingrodder]

Russ, I checked for potential shorts and didn't find any obvious problems.  I also rechecked for the proper electrode position in relation to the nozzle, etc.  I currently have my preheat temperature set at 200 F.  I may up that a little bit in case there is some contamination.

[Russ]

ShopSpecialties might be on to something.  I had to replace the o-ring in my ckburner just a couple of weeks ago because it was sucking air.

I have a new Honeywell R7284U1004 sitting on the shelf waiting to be installed.  I wonder if it can cut the spark when it sees flame and turn it back on if something fails?

[ageingrodder]

Craig at CKburners suggested the o-ring also.  I plan to replace it as soon as I figure out the size.

[Russ]

It is a size 007.

I updated my post to include the size:
http://wasteoilheaterforum.com/index.php?topic=453.0

[ageingrodder]

I replaced the o-ring and although that seems like it may have helped, it didn't fix the entire problem.  I think I'm getting plenty of fuel because I'm getting puff-backs.  Beginning to think there may be a fuel contamination issue or igniter issue.  I'll look into that tomorrow.

[CBTech]

If it settles down after 4 or 5 tries, I agree with ShopSpecialties, I believe you're sucking air somewhere.