Few issues are more pressing for a homeowner than a problem with your heating source. When an oil furnace won't start, there are a few common reasons why. Keep in mind that while you may be able to resolve some furnace issues on your own, most are best left to a professional.

Appliances in basement
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Home furnace in basement with other appliances


Hot water heater , gas furnace and air conditioning unit
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Furnace and hot water heater below home

An oil furnace is a large appliance that is used to heat a home. Oil is pumped to the furnace and is ignited. The heat from the fire warms the home through a duct system. There is a restart button on the motor that allows you to reset the system. If the furnace doesn't stay on after pressing the button once or twice, you have to troubleshoot the appliance.

Bubble or Clog

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Man adjusting thermostat

If you allowed your oil tank to run dry in the past, this may be the root of the problem. When the tank runs out of oil, sludge gathers at the bottom and can clog the pipelines. Due to the interruption of oil flow a bubble of air may have formed in the line, or water in the tank could be preventing the furnace from firing.

If you are familiar with the connections, you can purge the air by opening the valve on the oil pump. Oil will come out, followed by the air bubble. Inspect the oil for water. The problem might also be resolved by replacing the nozzle, which is inexpensive. For the sludge problem, a hex-head pipe plug has to be installed to push the sludge back into the tank. If you do not know where the valve, pump or nozzle are, leave this repair task to a professional.

Faulty Burner Assembly

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Technician and woman at thermostat

A faulty motor (also called the burner assembly) could be the source of the problem when an oil furnace won't start. A motor may fail if too much oil gets inside. If your problem is a faulty motor, you are going to have to call a service technician to your home to replace it.

Lack of Oil

Close up of Oil
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Oil, close-up

The most basic reason why your furnace isn't running is because you do not have enough oil. The furnace cannot fire up without fuel flowing from the tank. If the gauge is showing that there is oil in the tank, it is possible that the gauge is broken. If all other attempts to fix the problem aren't fruitful, schedule a delivery for a small amount of fuel to see if that solves the problem.


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Furnance unit

If your troubleshooting doesn't yield results, you have to call a technician. Examine your warranty to see if you are covered for repair or eligible for a replacement. To avoid these problems in the future, keep your oil tank at least one-quarter full. Change the fuel filters frequently. If there is no activity when you press the reset button, it could be a problem with the electrical fuses.

If you have a home warranty, problems with an oil furnace may be covered. If you are in a low-income household you may be eligible for energy assistance from your state, which helps cover your oil bill and furnace repair costs.