oil burner stutters, hesitates

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Old 01-10-12, 05:04 PM
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oil burner stutters, hesitates

Hey and thanks for the forum/help

I have a 15 year dunkirk steam boiler with a beckett afg50 burner. I assume the burner is original. I do have the boiler serviced annually by a (I hope) a well recommended burner servicing company. The point is I am a believer in preventive maintenance for the boiler. The boiler was annually serviced in september 2011.

Once last tuesday and once ( 1week later) today the burner hesitates/stutters while running The stutter occurred after the boiler has been running for 10 minutes. The burner does not cycle off but hesitates then refires a second later. The tank is 3/4 full. I did have oil delivered the day/night the first stutter happened. The hesitation that night made me think some crud had gotten stirred up in the tank/ clogged the line. But I looked at the filter and it was pretty clean (replaced 4 months ago during annual tune up). The fact that almost 30 gallons burned in between the stutters makes me think it is not crud/clogged line/air. I suspect maybe the pump is failing and/or the motor (the motor runs the pump, no?).

I am going to have the pros fix it but am trying to avoid the multiple service calls for what may be the culprit. Any way to test the pump to know if it is failing? To note after is stuttered today I shut the boiler down and left it for 3 hours. It fired right back up when I turned it on and ran flawlessly for an hour before hitting thermostat temp.

Therefore I suspect the pump or motor. Thoughts?
 
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Old 01-10-12, 05:30 PM
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It could be related to the pump...

Have you ever witnessed the burner servicing?

Do you know if they changed the 'strainer' inside the pump housing?

There may possibly be a bad 'coupler' between the pump and the motor.

There may be some air in the fuel supply.

Where is your tank located in relation to the burner? indoor/outdoor? (shudder) underground ?

Do you know if there are 1 or 2 fuel pipes feeding the burner?

Does your tank feed from the 'top' of the tank, or the 'bottom' ?
 
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Old 01-10-12, 06:43 PM
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I have never witnessed annual work but seems thorough-- test efficiency, temp, CO2, standard cleaning/vacuuming, new filter, new nozzle, burner adjustment. This year the lwco needed cleaning which they did, wife said the tech worked for 2 hours.

Thinking the same about the strainer, no idea if they did this but would ask for sure. , same idea with coupler. The strainer looks to be pretty accessible from what I see in the diagrams for me to perhaps check.

Re air, do not think a week would pass between stutters to be air in line--even if air leak somewhere it would be more regular stutter right? I did bleed the air from the pump till it ran pure oil after looking at the filter but that was 1 week/ 30 burned gallons ago.

Tank is indoor, same level as boiler, about 6 foot run to burner, one pipe. the filter is located at the tank which feeds from the bottom. The filter was actually pretty clean when looked at last week. If the nozzle was clogged I would expect more consistent stutters but maybe some crud is working slowly through the line.

Once the stutter starts it seems consistent , every 30 seconds or so I have never let it run on more than a few minutes when noticing the stutter. No idea if it may have happened when asleep/away. Any idea if a bad pump or motor would consistently misfire once it starts acting up?
 
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Old 01-11-12, 05:21 PM
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same idea with coupler. The strainer looks to be pretty accessible from what I see in the diagrams for me to perhaps check.
The coupler is a plastic or rubber tube with two plastic 'inserts' in each end. One slips over the 'D' shaft' of the motor, the other over the 'D shaft' of the pump. That plastic gets old and brittle... When I last changed out the motor on my own burner, when I pulled the motor, the coupling fell out in pieces. What was holding it together, I don't know... but the point is that one end could be 'stripped'. Maybe don't slip until it's warm...

Any idea if a bad pump or motor would consistently misfire once it starts acting up?
Still could be a symptom of clogged strainer. Or clog somewhere else in system... a VACUUM GAUGE on the fuel supply might be telling.

It could take the pump a while to build up enough 'vacuum' to cause problems if the strainer is clogged up.

If you take apart to investigate, make sure you have new strainer and gasket on hand before starting.

Check that there's no air leak at the filter housing! It could take a little while to pull an air bubble through the system and into the burner.
 
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Old 01-12-12, 12:26 PM
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Oil Pump, Strainer, and Strainer Gasket

If you decide you need a new coupling and/or strainer and can not locate these items locally, here is one online source:

https://keithspecialty.com/

coupling-item no. 66-355

If you have a Suntec oil pump, the strainer would be either item 66-340, 66-342, or 66-344 depending on your specific oil pump model. The new strainer comes with a replacement gasket.
 
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