My oil furnace is not lighting every time the themostat calls for heat. Sometime it works fine and other time it will not light and I have to press the reset button and then it sometimes does not start. Fuel is getting into the fuel chamber. Sometimes the furnace will light after a lot of fuel has been pump into the chamber with a loud bang. Please help

You have a ignition problem.
Weak ignition transformer or
Defective/dirty spark electrodes or
Partially restricted nozzle or
Loose wiring.

I do not recommend operating this furnace under these circumstances.

If the reset is pressed to many times and too much oil gets into the combustion chamber not only will you have a loud bang but you could end up with a uncontrolled burn which can lead to blower fan/fan limit control damage to say the least.

If you are not familiar with a oil burner and can do the necessary repairs I suggest you call a professional repair person and get it fixed ASAP.