Survivalgene:

When you say "pusher motor" on the exhaust flue, I am guessing you have a newer high efficiency oil burner.

The way that works is the "pusher motor" should come on first to start the draft before the oil gun fires up. They have vacumn sensors on those types of furnaces that will not allow the oil gun to fire if there is not sufficient draft in the exhaust flue.

If the oil gun is firing, than the pusher motor is working and the exhaust draft is sufficient. If it starts, clanks and then shuts down, the oil pump , the electric motor, or the motor to oil pump coupling may be bad.

If the description you gave me is correct, the easiest "diy" method is to buy a rebuilt exchage complete gun assembly of the same size and change it out.

Be careful that the oil nozzle on the rebuilt is the same spray pattern and length of spray as the original, and that the gun barrel is the same length from the mounting flange to the end of the barrel. The design and dimensions of the gun that hang outside the furnace only affects the attachment of your oil supply line which is usually flexible copper that can be adjusted to a certain extent.

When disassembling the gun from the furnace, make sure you shut off the oil supply from the oil tank, and have a tin can handy to catch the oil that will drip out of the tubing at the oil connection to the gun.

Good luck!

Bountyhunter