Monitor 41 shows flashing burner lights and will not ignite

[Venkman]

I have a M 41 that has been sitting idle in my garage since 1996. Prior to that it was used for about 2 seasons with no servicing.

I drained what fuel I could from the sump and checked the plastic filter. The filter was clean and the old kerosene was yellowish in color.

I took out the solenoid from the top of the fuel box and looked in the hole as best as I could and it looked clean and free of gunk.

I have no external fuel tank so I jury rigged a 1 qt coffee can so that the bottom of the can is 16" above the base of the heater to act as a fuel tank (yeah, I know, shade tree, red neck mechanic).

On the 1st attempt to light after slowly depressing and releasing the fuel set lever 3 times I had 4 burner lights on steady, with intake fan running and a quiet fuel pump (not chattering or banging). The igniter housing at the base of the burner got warm. I had no ignition after waiting quite a while after the burner lights came on. I then pushed the off button, waited a few minutes and started the start sequence again. This time I had all 8 burner lights but they were flashing, igniter housing was warm to touch, and the intake fan working. Again the burner failed to light. I can feel air flow exit the exhaust pipe from the intake fan, so I know the air is not blocked.

I know there is fuel in the pump box because of the amount of kerosene that I had to pour into the can.

I tried to remove the thin capillary line from the burner to see if fuel was coming out but it is quite difficult to remove and I did not want to break it.

Is it just a threaded connection to the side of the burner can?

What kind of fuel flow should I expect to see from the end of that capillary tube?

Should I remove that capillary tube and blow air through it?

Thanks

[hawkins111]

Show us a picture of your fuel tank?

[Venkman]

There it is.

The manual says that the bottom of the fuel tank has to be a minimum of 16" above the surface that the heater sits on. The set up is crude but hopefully it provides enough inlet pressure coupled with the fuel pump output

[hawkins111]

That tank is not high enough to give you the proper head pressure. Put it about the top of the stove and it might work.

Tom

[Venkman]

The pressure from the fuel pump is not enough I guess? I was hoping that the 16" head from the bottom of the can would be enough. Oh well back to soldering.

Thanks Tom

BTW what kind of flow would you expect from the end of the capillary tube when the head pressure is correct?

[hawkins111]

You should have .319 gph on high. Unless you have a flame sensor bypass you will not be able to measure the fuel flow. More to the point, the fuel pump either works or it does not work. If you do not get any flow at all you should look at the air safety switch. Make sure the system is wired correctly and the little hose is not cracked. If you get flow from the pump until the stoves goes in to shut down then I would say the pump works fine. My test tank is 2 gallons and it has to be higher than the stove top to provide the 2 PSI needed to get through the pipes and filter.

[Venkman]

I took off the small capillary tube from the top of the solenoid to the burner can and it was dry at both ends. This was after I shut the heater off and unplugged it. The opening at the top of the solenoid was dry also. The hose is not cracked on the air switch, so maybe the switch is bad or, like you say, the fuel pressure is too low because of the tank's height.

Is there a way to test the air safety switch?

[hawkins111]

Try to start your stove and put your finger on the pump. When the status lights come on you should feel a thumping in the pump. If you don't feel the thumping your next step is to by pass the air safety switch, i.e. put a jumper between the spades that have wires on them. Do not lose the positions of the wires. Use the search feature on the site and read all the posts about the air safety switch and fuel pump. I don't think you have the tank high enough or enough fuel in the tank.

[Venkman]

Good info. I will get a larger tank and raise it higher. I don't feel any thumping in the pump when I try to start it, so I may try bypassing the switch after I try the new tank.

[HayZee518]

you mentioned testing the air switch. take the rubber tubing off the air switch. then, using another piece of tubing on the fitting, blow into the tubing. if the switch is working you may hear a click when the microswitch closes. -or- with the cord unplugged from the unit use your meter on RX1 and two probes on the spade terminals on the switch. with air pressure on the tubing, then switch should close and will indicate full needle deflection towards infinity.
On the cappillary tubing, strip back a length of 24 ga telephone wire and see if you can push the wire into the tubing all the way from one side to the other. Look into the end that goes into the combustion pot and use a one-eighth drill by hand drill into that end. it will remove any carbon inside.

[Venkman]

I ran the telephone wire through the tubing and put the drill bit into the opening in the combustion pot with no problem. No apparent obstructions.

Do you have any idea of the size of the rubber tubing that connects the air switch to the intake fan?

[HayZee518]

cut off a small piece and take it with you to a plumbing shop or home depot or lowes and match it up. poly tubing will work but it cracks over time if you plan on replacing the whole length.

[Venkman]

I took out the flame sensor and it looks gray and discolored as you would expect from heat but when I wiped it with a tissue it was clean and no carbon came off it. Should it be polished or clean with something like bronze wool before being reinstalled?

[HayZee518]

even if it looks shiny when you're done cleaning it, it'll turn a black color once it's in the heat path. what you are looking for are no electrode to porcelain deposits which may short out the sensor.

[Venkman]

Thanks Hayzee. Is there any need to polish it shiny before putting it back, or just make sure there are no carbon deposits on it?