On Tue, 23 Dec 2014 23:45:44 -0500, micky
wrote:

I don't think we know that it lights. It may just stay on until the
usually 45 seccond start-up time expires. "On" meaning the motor runs
and powers the fan and the pump, but we don't know there is a flame.


There has to be some sort of "flame door". A little (usually round)
door to open and see the flame. Open that door and watch what happens
as it starts. Do you see a flame?

This is what you need to do first.

Basically you have two things happening in an oil furnace.

The oil comes from the tank, thru a filter, and to a pump in the
furnace. Then it goes to the nozzle and sprays (like a nozzle on a
garden hose) It should be a fine spray.

Next is ignition. The transformer creates the high voltage. The
electrodes and insulators send a high voltage spark across the oil spray
and ignites it.

That's pretty much how they work. If you ever held a cig lighter in the
spray coming out of a can of spray paint, there will be a huge flame.
(I'm not suggesting you do that). But that pretty much sums up how an
oil furnace works.

There is one other system, and that is the circuit board and flame
sensor, which allow it to burn if it sees a flame, or shuts it down if
there is no flame after some seconds. If that was not used, the furnace
would keep pumping unburned oil into the fire pot, and you'd soon have
inches of oil in the fire pot which would eventually run out of the
furnace and make a huge mess, if not cause a house fire.

Since you know th motor runs, you dont have a blown fuse and are you
getting a spark? Is the oil spraying in the firepot? Is the flame
sensor not allowing it to keep running (often due to a dirty sensor.

Again, check for clogged filter, change nozzle, and check for a spark.

So,
1. Check for spark
2. check to see if the oil is getting into the furnace and spraying.
3. Check for a flame sensor problem, which wont allow it to keep running

Just like working on a car. You need ignition and fuel.

Do you know, if you remove the whole burner assembly, short across the
thermostat wires, connect to a fuel oil source, and connect it to an
outlet, you can burn them ouside of the furnace?

DONT DO IT INDOORS.
IN FACT, I DONT SUGGEST DOING IT AT ALL.
(However I have done it outdoors, and know a guy who used to use one of
them to heat metal for forging).

---
Maybe someone else can answer this. The oil furnaces I worked on were
in the 60's thru the 80's. Back then the circuitry was pretty simple.
But I never worked on anything newer. Do the newer oil filters have a
lot of computerized stuff?????