Furnace Troubleshooting – Ran Out of Heating Oil, Furnace Won’t Start – 2021 Guide

| Last Updated: June 10, 2021

Imagine it is the middle of winter, and you run out of heating oil. 

What will you do? 

In many situations, your heater will restart after you fill-up the tank. However, if it fails to kick back even after it is refilled, you might have to bleed and restart the furnace manually. Bleeding your furnace is a straightforward process, and you can carry it out safely after reading the following article. 

Photo credit: paylessforoil.com

What Happens To My Furnace When It Runs Out Of Oil? 

It is a common misconception among people that running out of heating oil will result in damage to their furnace. However, that’s not true. Furnaces typically come with an emergency switch that works as a safety mechanism, which automatically switches off the burner if there is no oil left to combust.

However, running out of heating oil can cause clogged fuel lines and filters. The dirt and residue in the oil collect at the bottom of the tank and get lodged into the fuel lines, causing the filter to clog. In such a case, it might become necessary to call in for professional assistance.    

How to Restart a Furnace that Ran Out Of Heating Oil

If your furnace runs out of heating oil, then you should follow the steps given below to restart it again:

1. Fill Up Your Fuel Tank

The first thing that you should do when the oil level in your furnace gets too low is to refuel the tank. Bleeding the furnace when there is hardly any oil in the tank is not going to work. 

2. Press the Reset Button 

After refueling your tank, push the reset button. Your furnace should start working automatically. You do not need to bleed the fuel line if your furnace restarts after you have had it refilled. 

Bleeding the furnace is related to fuel levels. If the oil level on your furnace touches the bottom of the tank, then you will need extra help to restart it. However, you can avoid this problem by arranging a refill before the oil gets extremely low.  

3. Turn Off the Furnace

If your furnace does not start even after hitting the reset button, you will have to bleed it to get it running again. Begin by shutting off the furnace. On many models, hitting the reset button shuts them off automatically, thus eliminating the need to turn the furnace off manually. 

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4. Keep Your Tools Handy

You will need a wrench, nylon tubing with a diameter of ¼-inch, and a cup or a beaker to catch the oil waste. Also, keep an old towel near to clean your hands.

5. Identify the Bleeder Valve

The bleeder valve is typically found on the side of the fuel pump and has a hex nut on it. Tun the nut to loosen it a bit so that you can turn it easily at the proper time. Make sure that you do not unscrew it completely.

6. Attach Nylon Tubing 

Attach one end of the nylon tube to the bleeder valve and keep the other end inside the container. If you do not have a nylon tube, you can just position the container under the bleeder valve. However, make sure that the container is directly under the valve to avoid making any mess.

7. Turn On the Furnace

Now, turn on the furnace and loosen the valve. You will see oil flowing from the valve. Allow it to drain until clean fuel comes out. Hit the reset button again if nothing comes out of the valve. If the furnace still does not turn on, you will have to call for a professional.

8. Tighten the Valve

Once a steady stream of clean fuel comes out, tighten the valve. Your furnace should turn on now. Remove the tube and enjoy the warmth. However, if your furnace does not start even after bleeding it multiple times, you may have worn out parts and need professional help.   

Bleeding the furnace is a pretty simple process; however, if you are still unclear about it, you can watch the video below to understand it more clearly.

Cautious Considerations for Working on an Oil Furnace

Having a complete understanding of the working of an oil furnace makes troubleshooting very simple. Moreover, it is best to keep the following cautious considerations in mind:

Know Your Furnace

The only kind of furnace that you can restart by bleeding is an oil furnace. In case you own a gas furnace or are not sure about the type of furnace in your home, then it is safer to call a professional.

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Ensure Safe Working Conditions

When you are working on a furnace, you are dealing with components that can get extremely hot. This can be quite dangerous if you are not sure about how to proceed safely. The furnace bleeding process should not be a safety hazard, but it is best to give priority to your safety. You should not start a project if you are not 100% sure.

Be Cautious   

Any homeowner can efficiently and successfully bleed and restart a furnace; however, you need to be confident about what you are doing. People who usually carry out do-it-yourself projects will not find bleeding the furnace too much of an issue. On the other hand, homeowners who are novices to this kind of work should call in a professional.    

When Do I Call in the Pros?

A professional technician can accurately diagnose the problem with your furnace. If at any time during the process of bleeding the furnace, you find something strange or lose confidence, then it is best to call in a professional. 

Also, if your furnace does not start after the bleeding process, you should let a technician take a look to correctly ascertain the problem. In case the bleeding process does work and your furnace restarts, but you find yourself doing it regularly, then it might be best to get a professional opinion.  


Adding oil to your furnace tank before it becomes completely empty is the best practice. However, if your tank runs out of oil unexpectedly, then you will need to bleed the oil line and clear the oil pump, filter, and nozzle. Also, you need to ensure that there is no sludge present in the tank, which could cause blockages. 

In order to eliminate any worry or stress from running out of fuel, schedule an automatic heating oil delivery. This will ensure that you will always have ample supply to keep you and your family warm and comfortable during winter.  

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People Also Ask

Your furnace may have been serving you for a long time, but still, there might be some things that you may not know about it. Before starting any troubleshooting, it is best to have as much information as possible. The following answers will help you know more about this appliance: 

Will Letting My Furnace Run Out of Oil Damage it?

If your furnace runs out of oil, it simply stops working. Every furnace comes equipped with a safety system that disables the burner in case there is no flame. Although it is better if your furnace does not run out of heating oil, it does not cause any damage to the furnace.

How Do I Know When My Oil is Low in My Furnace?

There are a few signs that give you an indication that the fuel is low in your furnace. 

1. Your furnace will start making some noise while starting up. These may sound like loud roars or a series of bangs.
2. If you need to press the reset button once or multiple times every day, then it is likely that the fuel in your furnace is low.  

My name is Bob Wells and I am a retired HVAC tech from Washington state. I am currently retired and no longer do much with HVAC, however, I feel like I have a lot of knowledge in the subject and I wanted to create a website where I could talk about what I've learned and help upcoming HVAC techs. Find more info about me and HVAC Training 101.