Heil oil furnace question?

[Steve]

Hello, I've searched the archives for my problem with my Heil furnace but couldn't find anything so here goes.

My furnace is a 1978 vintage system. It is an oil fed / forced air system. I have been having a problem with it shutting down on its own. I've narrowed the problem to it becoming air locked and starving for fuel. All I have to do is open the pet c*ck drain, push the reset button and let it run into a pan until clear oil flows and close the pet c*ck and it then runs fine. This has been happening several times beginning last winter and now has happened just recently.

Things I have done or checked: a) Replace the oil filter b) Check the breather pipe for blockage on the oil storage tank c) Replace the nozzle d) Replace the flame sensor e) Tighten all fittings f) The tank is over half full

Any other ideas or suggestions? The furnace seems to run fine otherwise.

Thanks, Steve

[jolt]

One thing missing from your list g) Clean the pump screen

[Steve]

Thanks for the tip. Didn't even know the pump had one? Do I need to take the pump apart to get to it? Just wondering if the screen is plugged would the furnace even run at all? Or does it sort of clear itself when I open the drain pet c*ck? Thanks! Steve

[Pete C.]

The pump screen is accessed under the pump end cover on most pumps, should be like 4-8 screws holding the cover on I think.

Tightening the fittings may not always seal them and in some cases can make leaks worse. Cutting back, re flaring and replacing fittings is more reliable.

Do you have a single pipe fuel feed and if so is it gravity or suction? It it's a gravity feed from the tank and stays low all the way to the burner you usually don't get air in the line problems unless perhaps you have such an accumulation of sludge in the tank that it's blocking the outlet. If you take the filter off and put a pan under it do you get a strong fuel flow if you open the valve?

If you have a suction setup (drawing from the top of the tank) that is more likely to have airlock problems from the slightest leak at a fitting. Also consider deteriorated gaskets at the pump of filter as possible air inlet sources.

Pete C.

[Dan K]

Has something been replaced recently (like the burner)? Are there two lines going to/from the fuel tank?

When we had our burner replaced (middle of winter on the coldest day), the guy hooked it up, got it running , and said he would be back later in the week to tidy up the install and be sure everything was right. Well, he never showed up again and we didn't complain because the bill never showed up either. The burner ran fine for that winter, but later we found out what he needed to "tidy up". Seems that he never installed the checkvalve, or got it backwards. We literally ran out of fuel early next season when the tank was full. Took a different repair man no time at all to diagnose and correct the problem, and the problem has not returned for over 10 years now. I have no idea why the burner ran for as long as it did and why it failed when it did as I'm sure the tank had more fuel in it when it failed than when it was running that first season. I have no idea where this valve is or what it does but it sounds like it might be your problem.

Dan

[Steve]

Thanks Pete! I see the 4 cap screws on the end of the pump housing. I assume removing those should allow the cap to be removed and allow accessing the screen. Right now after just having reprimed the thing since yesterday, the furnace is doing ok but if it goes out again that will be the first thing I will do.

I have a single pipe fuel feed which I think must be suction? But the line comes out the BOTTOM of the tank and goes through the fuel filter and is routed up through the upper floor joists over to the furnace and then down to the pump. I have no leaks anywhere that I can see in between. If there's a leak wouldn't it be noticed as a fuel drip if the furnace is not running?

Also, if it goes out again I will remove the fuel tank filter and drain some out and see if there is any sludge. I put a new filter on last winter when I first started having the trouble and I thought I remember doing that at that time.

I'll also check for bad gaskets.

Steve

[Steve]

Thanks Dan! The only thing that has been changed in the last couple years has been the fuel tank filter. I have not noticed any leaks on it but I will double check that as well.

Steve

[Speedy Jim]

Before you yank the pump cover off, order the screen and gasket kit for that pump model. You won't be able to save the old gasket and risk having no heat without a new one.

You're saying that the tank is one floor *below* the burner? And it's a one-pipe system? Although that setup will work under the best of conditions, it is very prone to failure when there is the tiniest of vacuum leaks *anywhere* in the suction line. That could be the packing on a stop valve, the cover gasket on the filter, a flare fitting and on and on.

Go change the screen, but if you still have trouble either investigate vacuum leaks or change over to a 2-pipe system.

Jim

[Pete C.]

It sounds like he said the line comes from the bottom of the tank, goes up to ceiling level and then back down to floor level where the burner is.

As for the leak thing, it's quite possible to have a leak that lets air in under suction conditions and does not leak any fuel outward when the pump is inactive and the line is at a pretty neutral pressure.

Pete C.

[Steve]

Yes you have that right!

Then the leak would have to be up high somewhere? There are no joints between the filter (down low) and the pump (down low).

I'll let you guys know what I find or do if it happens again. I am too stubborn to call a repair man! Thanks!

Steve

[Pete C.]

The leak doesn't necessarily need to be up high. When the pump is running and fuel is flowing, a bubble of air could be sucked in from a leak anywhere along the line.

In a single line gravity feed setup where the line stays along the floor all the way to the pump the line remains under pressure all the time and there is little chance of sucking air in the line even if there is a slight leak.

In a single line suction setup where the line goes up above tank level (whether the line comes from the bottom or top of the tank makes no difference) the reduced pressure allows air to be drawn in from any leaks. These air bubbles will be very small, but they will be drawn along and accumulate in the pump where they can eventually cause the air lock.

With a two line suction system you can still draw in bits of air from leaks, but when they get to the pump they don't accumulate to problem levels because the excess fuel being pumped is returned to the tank via a second line instead of being returned to the pump inlet as in a single line system.

Other than the obvious advantage of finding any leaks in your feed line before they become bigger, adding a return line from the pump to the tank will most likely solve the air lock issues. Most pumps are designed for this and adding the return line is generally as simple as removing a plug on the pump and installing a fitting and the return line to the tank.

Pete C.

[Steve]

Hello again, We just got home from a long Thanksgiving weekend and the furnace is still working fine. The last things I did when it went dead about a week ago was to re-prime the system and then after posting this topic, I snugged up on all the joints and fittings on the line going to the pump. Prior to doing this when the furnace was still working and just before it went dead, when it started up it would sputter and shudder almost like it was going to erupt. But now it seems to start up as quiet and smooth as it ever has when it was working good. I'm wondering if it was sucking a bit of air all along and when it would start up it would be feeding an air/oil mixture and trying to ignite that which caused all the sputtering? Finally when it got a high enough air to oil mixture it would quit?

Thanks for all the great suggestions! Steve

[paul.flansburg]

You may be fine, but as it was mentioned I think by Jim, replace the screen on the fuel pump. If you haven't done this within the last two years it will need to be replaced. I replace several on a yearly basis's and the ones that I see are full of junk. It's probably in the order of 5 or 6 bucks........Replace it! Don't forget the gasket and if I remember correctly the screen should come with the gasket in the same box.

-paul

[Steve]

No doubt that the screen needs to be changed. It has never been even looked at. I'll see if my local Hrdwr store has the part!

Thanks, Steve