That tough leak


“Diagnostic troubleshooting” can often eliminate the misdiagnosed “blown seal”

By George Lanthier

Most of this article comes from one I did a long time ago, but it has to do with probably the most troublesome leak on an oil burner. It originates at the burner housing and in most cases the pump is replaced for an alleged bad seal. The truth of the matter is that most of us have never really seen a blown seal. Trust me, if you had you would remember it, and keep in mind, most pump companies will tell you that 99.5 percent of all pumps returned for blown seals are not, in fact, blown.

When I worked as a service manager one of the first things I had my apprentices make up was a pump kit. Do you know what should be in a pump kit? Well, here’s my spin on it.

First of all, a vacuum gauge and at least two pressure gauges. A 0 to 150-pound gauge and a 0 to 300-pound gauge. You younger techs can probably get away with just one (0-300), but as you get older a smaller scale to read really helps us old guys. I also prefer glycerin-liquid-filled gauges, but I am a fussy old bugger. Not only are they more accurate, but they also hold up better. I’ve used liquid gauges for 25 years and wouldn’t use anything else.

Next, a device called an “oil watcher.” You can get one from any wholesaler that sells the Mitco line or from Sid Harvey’s or from Westwood under the name “Clearview.” You could use an a/c sight glass, but I have used both and prefer the “oil watcher.” Although you could make up an “oil watcher” yourself, it’s just as easy to buy one all made up. Essentially, it’s a piece of 1/2-inch clear plastic tubing with hose barb to pipe adapters (Figure 1). Onto those pipe adapters go the connections to oil-line fittings, flare, swage, compression and whatever else they use in your neighborhood.

The rest of the kit is made up of fittings and adapters that let you get into oil lines of any size and anybody’s pump. To keep it all handy I keep everything in an old kid’s lunch box and I have my Riello adapters in there, too. You should also own a hand pump and I prefer the Firomatic brand hand pump (Figure 2), but as long as you own one, that’s what counts.

No CO2 blowout guns; I don’t believe in them. I do believe that they do blowout things though, like oil lines.

Did you know that a typical CO2 cartridge could develop pressures as high as 1,000 psi? Now, you put that onto a 20-year-old oil line that was not even rated for that when it was new and what do you think is going to happen?

So, you get to the job and find oil dripping out of the bottom of the housing and the fan and everything is wet with oil. Some people will tell you that there is no way to check a pump seal in the field with a gauge. If the pump is wet, the seal is gone, right? Not really. Can you check a pump seal in the field? Do you know how to do it? C’mon, fess up to Georgie, do you really?

In Figure 3, we have a drawing taken right from my all-time favorite pump book. Yep, it’s the Suntec Installation and Service Manual. You’ll find this procedure on page IV-7 and although I’ve modified it a bit the procedure goes like this:

Tighten all of the fittings and unused plugs on the pump after resealing with a good quality (non-Teflon) pipe dope.

Remove the inlet line from the fuel unit and install a vacuum gauge directly into the inlet port of the pump. If the unit has been running dry, pour some oil into the pump before testing it. Turn the burner on and bleed the pump.

When the vacuum gauge reads 15 inches of mercury, close off the bleed port.
Turn the burner off and the pump should hold oil for five minutes.

If you can’t establish 15 inches of vacuum, or the pump won’t hold, you have a bad pump or seal. I bet you’ve done this test plenty of times for vacuum by just closing an inlet valve, right? That’s OK if you just want to see if the pump will develop vacuum, but you have to do it this way to check the seal.

So, did you really know how to do this test and did you know you could do it on a two-pipe system, too? Yep, just remove the return line, remove the by-pass plug, plug it and go through steps 1 through 5 again. By the way, you’ll also find this procedure in the COHA Manual and the PMAA/NAOHSM/NORA Oil Heat Technician’s Manual. In other words, any place where you find procedures for doing it the right way. In addition, the test will work on anybody’s pump.

After doing the test, you find that the pump seal is OK and that the pump is “vacuum tight,” so where’s the oil coming from? Another thing to check is tube alignment and level. An awful lot of good pumps get kicked off burners simply for the airtube being out of alignment. Make sure that the airtube is pitched just slightly down to the chamber area. Not only is it right, but also when you have a chamber or where latent heat causes expansion of the oil in the tube the expanded oil has a place to go. The easiest way I’ve found to check this is to take an empty nozzle vial, fill it with water and tip it over inside the tube. If the water runs to the chamber and disappears, that’s one more thing to check off the list.

The next thing to check for is a nozzle-line leak and you will need a piece of newspaper. By using the newspaper, we’re going to check for a high-pressure vapor leak around the pump. You see the burner fans today are all turning so fast, at 3,450 rpm, that sometimes the smallest leak won’t show until the pump goes under pressure and then the fan sucks the oil vapor right into the housing. The vapor turns to liquid and, bingo, there’s your oil leak. Naturally, most guys suspect a seal leak because what you can’t see won’t hurt you. Know what I mean?

So, take a piece of newspaper and run it around the back of the pump and between the pump and housing. In some cases, those plug and vapor leaks will show up, but in this case, let’s say it doesn’t. Now what you need is a plugged nozzle.

In Figure 4a, we have a plugged nozzle that also acts as a very “cool tool.” The “cool tool” part of it is a Beckett “Z” dimension tool. It allows you to set the head to nozzle dimension on any “F head” and you don’t have to drop the burner off the appliance. This idea was first shown to me by Jim Dowling, a service technician on Long Island.

Using an old-style Delavan nozzle (Figure 4b), the ones where the parts fall out when you remove the filter, punch out the steel insert from the face of the nozzle by knocking the insert back into the nozzle body. Insert a 1/4-20 x 1-inch cap screw or round-head screw with the head ground down to fit. Get a 1/4-20 jam nut and a 1-1/2 fender washer. Check that the thickness of the jam nut and washer is 0.203 inches plus or minus 0.010 inches combined with a micrometer, or by using a burner and Beckett “T gauge.” You may have to substitute flat washers for the jam nut to get this dimension. Beckett states that the distance from nozzle face to the back of the head should be 13/64 or 0.203 inches. This is for F-0 through F-30 heads. Assemble the gauge by putting the screw in the nozzle and adding the jam nut, fender washer and nut. Use either lock-tite or a second lock nut to hold everything together. With everything tight, put the nozzle on a flat surface to check that there is no bend in the washer.

After I made up a few of these I realized that if a faucet washer was placed on the screw as it entered the nozzle I would have a plugged nozzle for this test, so ….

To use the tool for “Z dimensions” remove the electrodes and install the tool. Slide the gun assembly into the tube until the washer hits the back of the head. Mark the position with a scribe and remove, reassemble with normal nozzle and electrodes, line up the scribe mark to the tube and lock down. It is a lot easier than removing the entire burner and using a standard Beckett T gauge, and if you use the orange gauge on a hot burner you only get one
use of it.

For our test leave the nozzle line and drawer assembly with the tool inserted outside of the burner housing and the nozzle line connected to the pump and then turn the burner on. Just as the assembly comes to pressure a leak is noticed at the nozzle adapter to nozzle line connection. Wow, you’ve found it! By the way, remember my article titled “Nozzles?” It may be time to go back and re-read it. We’re eventually going to have all of our old articles on our Web site.

It’s about that easy, and the great thing is this was just a small oil leak, not a seal. It was easily fixed and another innocent pump was saved from being condemned, all for a little bit of pipe dope and a few turns of a wrench. Did you happen to notice that I worked my way from the pump to the nozzle? That’s called using a “system” by most of us, but I also call it “diagnostic troubleshooting” in my seminars. A methodical way of getting the problem fixed and not running around like a headless chicken while doing it. Try it sometime and you’ll be amazed how much easier it is, and when you work easier, you work smarter. By the way, it’s tricks like these that are found in our “Advanced Seminar” series.

See ya.

George Lanthier is the owner of Firedragon Enterprises, a teaching, publishing and consulting firm. He can be reached at 132 Lowell Street, Arlington, MA 02474-2756. His phone is (781) 646-2584, fax at (781) 641-7099 and his Web site can be found at

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