How to Prime an Oil Furnace

If you have an oil furnace, it will run out of oil and need priming to restart it. It isn't advised to let your furnace run out of oil, but it happens at times when you try to conserve fuel.

After the tank gets low, air can seep in the furnace, which means insufficient oil transfer. You should be able to prime the furnace yourself. Here are tips to prime an oil burning furnace.

Prepare to Work

For this project, you need:

  • work gloves
  • safety goggles
  • 3/8 or 7/16  wrench
  • glass jar or metal bucket
  • non-clumping kitty litter or dry coffee grounds
  • rubber hose
  • heating oil

Look for a toggle switch to shut off the furnace. If you can't find the switch, shut off the furnace from the breaker box.

If you find oil seeping on the floor, don't proceed. It means the combustion chamber needs replacing. Soak the oil with kitty litter or coffee grounds.

Ensure the emergency switch is on. This switch is commonly located near the basement entrance or building code. Set the thermostat higher than normal. 

Buy home heating oil as soon as possible. K1 Kerosene is  a good temporary substitute, but it is more expensive. Diesel is another option while you wait on more oil. If you want to reuse oil, store it in a clean container.

Find the Bleeder Valve

Find the bleeder valve on the oil pipe by following the copper pipe that runs from the tank. The bleeder valve is a small spigot knob with a handle on one side of the fuel pump at a four o'clock position. It resembles an auto brake bleeding port.

Set a glass jar or metal bucket under the valve. Don't use plastic containers as the oil will melt them. Add some kitty litter or coffee grounds to the bottom to prevent splashing.

Bleed the Tank

If a nut covers the valve, use a wrench to detach it. Loosen the valve handle with the wrench. Restore power to the furnace.

Oil should start collecting in the container. If there is no oil, push the red reset button on the pump.

Hold it for several seconds, and watch for oil to come out of the port. Repeat this procedure two more times. If the bucket or jar is too big for the spigot, attach a rubber hose to the spigot, and place the hose end in the container.

After the oil has finished spilling, detach the hose and tighten the bleeder nut and valve. The furnace should come on. Bleed the furnace again if it doesn't ignite.

Don't bleed more than three times. Refill the tank.

Furnaces that still won't ignite could mean damaged fuel lines. If you don't trust your skill, or the furnace still won't start, contact an HVAC service like Laroc Refrigeration-Metal Division for more advice.