I have replaced the following with the problem still happening: replaced the primary control(R8184G 4009), cad cell--the oil unit was service at the beginning of the heating season. Ran like a champ.

Now for the past two weeks with new parts the problem is: Oil burner starts with a flame for about 15 seconds, then flame out for about 12 seconds---then unit flames on until heat temp is reached. Happens exactly the same all the time with new parts. I have a two pipe system, oil lines have flare fittings---everything is tight. I checked the filter still like new from the service. I also primed the oil pump--even though I have a two pipe system. Why is this happening. Now when there is the 12 second no flame and when it comes back on it is a normal ignition --no roar or big explosion just a normal ignition. I have a Beckett AFG unit, Weil-McLain Gold, Honeywell Primary Control/cad cell, High Limit, Suntec two stage oil pump (3450 RPMs), and an Emerson motor that matches.

Do you have an electric oil valve installed as shown on the below link drawings? The problem has to be in oil delivery since if it was ignition you would hear about it like in Boom. LOL

http://customer.honeywell.com/techlit/pdf/PackedLit/69-0618.pdf

No electric oil valve

It has to be fuel delivery but why the perfect timing I have no idea. The 15 second/12 second thing is very strange. What kind of tank do you have/ Above or below ground? Have you checked the vent on the tank or any anti spill device in the vent?

Tank is in the ground (1000 gallon tank), vent is unobstructed and clear--I measured the oil and I have 510 gallons in the tank. There is no leaking ---I monitor the oil burned by measuring and from Dec 9 to Jan 11(in which the burner was fine) ---from Jan 11 to Feb 01 >>burning about the same amount of oil.

If it is an in ground tank then it is drawing from the top so the old floating object at the bottom of the tank deal is not involved.

My last thought on this is the oil pump and king coupling. I am sure when you set up the burner you tested and set the oil pressure properly just as any service person would do but to confirm the issue put your gauge back on the units oil pump and fire it over. Watch the gauge as it runs and see where the pressure goes during the 12 seconds of flame out. This will confirm at least that the pump is good but it could also tell of a possible bad check valve in the pump or a slipping kin coupling.

Many years ago there was a delay style coupling that would wind up before exerting pressure on the pump to produce oil. Those items caused much trouble when they got old and really produced some strange effects. The possibility of you having one of those left on your burner is slim to none but I just thought I would mention that fact.

Post back with your oil system operating pressure during normal running and also during flame failure.

I am at work---will check later -- the entire system was installed new in 1997. Suntec two stage pump(model B2VA-8216) 3 GPH (100 - 150 psi, R.H. Rotation, #2 Fuel). Pressure was fine at the beginniung of the heating season but things due happen. Will get back to you... thanks.

Ok