Bleeding an oil pump cause an explosion?

Old 11-13-08, 01:08 PM
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Bleeding an oil pump cause an explosion?

I sure donít want to bother this forum with seeming trivialities while people have real problems, but I think an opinion to the safety issue below from the knowledgeable people on this forum would be very valuable. The following statement came from a HVAC professional on his website where he was discussing a situation in which someone called and asked how to bleed their oil pump:

ďMost people who read my posts over the past years know that I don't recommend anyone bleed their own pump as they also have to check combustion with tools they don't have or they are just guessing as to an explosion or not in order to save some bucks.Ē

Is that actually correct? I donít understand at all? I changed my oil filter myself for the first time and then bled the pump. I didnít think I was taking a big risk Ė as long as you make sure you are not letting a lot of oil through to the burner head without ignition while you are trying to bleed.

In other words, if you change the filter I thought you are then supposed to get out any excess air by pumping out the bleeder valve for about 10 seconds to clear any air and then immediately close the bleeder valve. That way you will not let oil build up in the chamber ( I think I mean in the chamber anyway?) but you will clear any air. If I understood my boiler manual I believe thatís what is says.

And I believe Danfoss (or another pump mfgr.) says make sure the bleeder valve is all the way open when you start so you are not letting oil through to the nozzle line. (Not those exact words Ė but I thought thatís what they meant).

I donít understand how you could use combustion tools during the bleeding process, or why you would use them after you are done bleeding? Or would he mean you should use the combustion tools when youíre done and the burner is running to check to see if you did in fact get too much oil in the chamber and thus should shut off your burner for safety ? (If that makes even the slightest sense?) Very confusing!

Iíd sure like to know the answer - as I would hate to wind up in DIYíer heaven with the wrench still clasped in my hand.

Any thoughts would be much appreciated!
Old 11-14-08, 10:05 AM
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You should be able to do it

AFAIK, as long as you still have air in the line when you're bleeding it, you're doing what's necessary. (Take this with a grain of salt, as I am not a "pro". Hopefully someone else here will chime in...) An air bubble in the line just means that you'll probably have to bleed it again, once it reaches the pump.

Who is your pump manufacturer, model #, etc? Are you able to get oil flowing at all, or do you still have air?

I found the website you're referencing. While I suggest you get the burner serviced yearly, I see no reason to call them simply to bleed it.

While bleeding, did the new oil filter get saturated, or no?

Let us know.
Old 11-14-08, 11:39 AM
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Normally, when you bleed the oil line you should have cleared the air within 10 to 15 seconds and should tighten the nipple as soon as you see oil.

I think his warning is valid. If you take too much time to bleed the line and allow oil to accumulate in the combustion chamber (with no ignition), when ignition takes place you will get a loud bang or worse an explosion.

This is why all oil furnaces have either a stack sensor or photoelectric sensor to shut down the furnace if ignition does not take place shortly after the thermostat calls for heat.
Old 11-14-08, 12:30 PM
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This is where a pre-purge oil valve comes in as another asset. You have 12 - 15 seconds before the valve will open, or can pull the coil off the stem and it will never open. You can bleed unitl the control locks out.

At the same time if the pump is good it can't spray oil until pressure builds. Which it won't with an open bleeder. There is a cut off valve in the pump to prevent oil from entering the line until there is enough pressure.

Even if you do close the bleeder with the motor running and oil does spray, the ignition will light it. Then you'll jump and quicky turn off the burner...

Old 11-14-08, 05:56 PM
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I wonder if maybe more context of the original article is in order ?

Perhaps he was talking about after a homeowner might have pushed the reset on the primary a half-dozen times ... or perhaps a fuel run-out, and the homeowner tries to get the thing going again ... any case where there might be oil built up in the combustion chamber ?

I don't see anything inherently dangerous about bleeding the pump as long as there is a basic understanding of the process and the possible dangers...
Old 11-14-08, 06:00 PM
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Bleeding Pump

Simply changing the fuel filter & bleeding the pump will NOT cause an explosion unless there is some other problem & combustion test equipment cannot be used until the flame is burning. Though not impossible, it is difficult to make oil explode.

Reno1962 may be well intentioned but the information given is WRONG. One should not close the bleeder as soon as you get oil. Fuel should be allowed to flow for at least 10-15 seconds after the last air bubble is seen.

Unless you are using a small bottle or something else which you can get over the bleeder port, put a hose on it. Failure to do so can result in fuel being sucked in thru the air band of the burner.

Regardless of the brand of pump, usually opening the bleeder 1/4 to 1/2 turn is ample.
Old 11-14-08, 09:13 PM
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Thanks very much folks!

Iíve learned some very good stuff here. (NJ you hit it right on the head. The guy did run out of oil and called the pro to learn how to bleed the pump.)

My burner is a Beckett AFG which has a Danfoss BFPH 071N1151 pump. I really didnít have any problem whatsoever bleeding at the pump and never opened up the canister to look at the oil filter again!

(But I am curious however about what a new filter looks like after running for an hour or so. I know itís simple but I canít figure out how the filter catches stuff and how the oil flow works! I guess it must saturate immediately to pass oil? See, how little I know! Oh well, Iím working at it. )

I only did the bleeding process because I thought you were always supposed to do that whenever you change the filter to purge any air in the line. As far as I can tell everything was flowing fine immediately after the bleeding was done - and it still is. So I think allís Ok mike316 . Thanks.

Your comments here folks got me to look into terms like stack sensor, photoelectric sensor, prepurge, control lock out, etc. (I didnít know stack sensor was a safety device Ė donít know what I thought it was? But I remember wondering not long ago why I didnít have one?)

I happened to find the following page that has definitions related to your comments :


My boiler manual does in fact seem to match what Al says. That is, it indicates you can bleed until the control locks. It states that if you let it bleed for 10 seconds in a steady stream with no bubbles and then close the valve, the burner should fire immediately. But if not you need to reset the primary control lockout or the motor lockout. They didnít seem too concerned if that happened.

I did use a transparent hose down into a pan and I got hardly any splash at all. Went a little wild on the open bleeder valve part since I was really afraid Iíd been running with the valve sending Ĺ to the nozzle and only Ĺ out the bleeder valve. Iíll keep it to ľ or Ĺ turn next time. I didnít know the pump pressure concept mentioned above by Al.

Looks like all of you folks agree that bleeding the pump is not so dangerous that a DIYíer really should be discouraged from doing it - as long as he(she) understands whatís going on and the possible dangers. That certainly answers my question and I think the above comments will be very beneficial to many other folks as well.

Thank you for all your time!

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