Free Boiler Restart

What Happens When You Run Out of Heating Oil?

More often than not your oil boiler will NOT just restart after you put oil back in your oil tank. We generally find that 8 out of 10 of the properties we attend the boiler needs a little assistance before it fires back up again. DON'T panic if we are delivering your oil we can offer FREE Assistance & Advise.

Here’s what you need to know.

1. Your Boiler Will Shut Down

When your oil tank runs out of fuel, your boiler will automatically shut down to protect itself. Oil boilers need a steady flow of fuel to operate properly. Once the supply is interrupted, the system goes into lockout mode — a built-in safety feature that prevents damage to the burner or pump.

You’ll usually notice:

The heating and hot water stop working.
A red warning light appears on the boiler’s control panel.
The boiler won’t restart, even after refilling the tank, without a reset or bleed.

2. Air Can Enter the Fuel Line

When a tank runs completely dry, air is drawn into the oil feed line. This trapped air stops oil from reaching the burner, meaning your boiler won’t be able to fire up again even after you’ve had an oil delivery.

In some cases, you’ll need to bleed the oil line to remove air pockets before restarting the boiler. This is a simple job for a qualified heating engineer, but it’s not recommended as a DIY task unless you’re experienced — as doing it incorrectly can cause leaks or system damage.

3. Sludge or Sediment May Get Pulled Into the System

Over time, sludge and debris build up at the bottom of an oil tank. When your tank runs low or empty, this sediment can get drawn into the fuel line and clog filters or injectors.

This can:

Reduce boiler efficiency.
Cause the burner to smoke or fail to ignite.
Lead to costly repairs if not cleaned out properly.

That’s why it’s important to let your oil settle for at least 30 minutes after a delivery before trying to restart your boiler.

4. Your Heating System May Need Bleeding or Servicing

After an oil run-out, even if the tank is refilled, your heating system might need bleeding to remove trapped air or a service to clear any blockages.

A professional engineer can:

Bleed the fuel line safely.
Replace any clogged filters.
Check that the burner and pump are working properly.
Restart the boiler and test the system.

5. Prevention Is Better Than Cure

Running out of heating oil is more than just an inconvenience — it can also cause unnecessary wear on your boiler. To avoid it happening again:

Check your oil level regularly, especially during winter.
Set up automatic top-ups or alerts with your supplier.
Install a tank monitor, which can notify you when your oil is running low.

These simple steps can save you from cold nights and costly call-outs.

Final Thoughts

If you’ve run out of heating oil, don’t panic. It’s a common issue, and with a quick refill and a professional restart, your system can be back up and running in no time.

At Heating Oil Today, we’re here to help. If your boiler won’t restart after an oil delivery, our experienced heating engineers can safely bleed, service, and restart your system — getting your home warm again quickly.