Oil Boiler Not Firing Up – 8 Problems and How to Fix Them

If your oil boiler isn’t firing up and is creating problems with your heating and hot water supply, this is the guide for you. We will explain the 8 most common reasons why an oil boiler refuses to fire up and show you how to fix them.

All boilers have issues firing up from time to time and oil-powered boilers are no exception.

It can be hugely frustrating as often it will leave you without central heating and hot water. Inevitably, this sort of issue always arises at the worst possible time.

In this guide, we will identify the eight most common reasons why an oil-powered boiler might refuse to fire up. Some are simple issues that you can probably fix yourself while others will require some professional support.

This article covers the causes of most oil boiler fire-up issues so we are pretty confident that by the time you have finished reading, you will know why your oil boiler won’t fire up and have a good idea of how to fix it.

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The Top 8 Problems And How To Fix Them

In this section, we will detail the eight most common issues with oil boilers refusing to power up and how to fix them. We are pretty confident that this article will cover the cause of most issues although there are some other rare things that can lead to fire up issues too.

If you don’t think any of the reasons detailed in this guide are causing your problem, you will need to get a qualified engineer to take a look at your boiler to get to the bottom of the issue.

Equally, if you are in any doubt about taking on any of the DIY fixes we suggest in this guide, you should also contact an engineer. Boilers can be dangerous and we wouldn’t advise anyone to try any fix they were comfortable and confident doing.

  1. Run out of Oil

The most obvious cause of an oil-powered boiler refusing to fire up is that it has run out of fuel. You can usually check this by looking at the gauge which is usually located either on your oil tank or remotely somewhere else in your home.

How to fix it:

If your tank is completely empty or only has a small amount of oil left at the bottom, this is highly likely to be the cause of your problem.

You will need to call your regular oil supplier to come and fill it up. If they are unavailable, other companies will often offer a top-up service to keep you going until your main supplier is available. However, this is likely to cost more than your regular rate.

  1. Incorrect Pressure

If your problem is not being caused by a lack of fuel, the next thing to check is your boiler’s pressure.

The majority of boilers are designed to run at a recommended pressure of 1.3 bar, but this can vary from one model to the next so it is worth checking your boiler manual to be sure.

If the pressure in your boiler gets too high or too low, this is likely to cause the boiler to lockout and this will stop it from firing up.

How to fix it:

If the pressure in your boiler is too high you will need to bleed some water from your system to reduce it.

This can usually be done from the radiator bleed valve but you will need to have a container and a cloth on hand to clean up the excess water. Another way to remove water from your system is to use the drain cock.

If the pressure in your boiler is too low, you will need to add pressure to the system. First, it is advisable to check your system for leaks because if you add water to a leaking system you are likely to cause more water damage elsewhere in your property.

If there are no leaks, you can add water to the system by opening the valve on the external filling loop.

  1. Blocked Condensation Pipe

All boilers create condensation which is then vented outside the property. However, the pipes which are used to remove this condensation can get blocked by debris and also freeze in cold weather.

If the weather is below freezing outside, there is a pretty high chance that this is the problem and if the condensation pipes are frozen, your oil-powered boiler will go into lockout as a safety measure.

How to fix it:

This is a simple issue to resolve. First, you will have to locate the condensation pipe coming out of your boiler. It is usually a white pipe that is 21.5mm in diameter but could be larger.

Once you have found it, check for obstructions and freezing. If it is frozen, you some warm (not very hot) water to thaw out the pipe. You might also want to consider fitting some lagging around the pipe to prevent the issue from reoccurring.

With that done, reset your boiler and it should now fire up and continue to work as usual.

  1. Faulty Fan

If there is an issue with your boilers fan, it is likely to stop your boiler from firing up. The fan is a crucial component in the boiler as it helps to push the dangerous gases your boiler generates down the flue pipe and outside your home.

If there is any indication that your fan is not working, the boiler’s failsafe functions will kick in and it will stop working,

How to fix it:

You will probably be able to tell if your fan has an issue because it makes a small humming noise and vibration when it is running. If this isn’t present, you will need to get the component tested. To that and make any repairs or replacements that are necessary, you will need the assistance of a qualified engineer.

  1. Faulty Air Pressure Switch

The air pressure switch is the component within your oil boiler which enables it to recognise when the fan is working. It does this by measuring the air pressure in both the boiler and the flue.

If it appears as if there is a problem with the fan in your boiler, it is just as likely that the air pressure switch is actually causing the issue. This would again cause the boiler to refuse to fire up, so it is a good idea to get this checked out too.

How to fix it:

If there is an apparent problem with the fan, you will need to get an engineer out to look at your boiler. They should take a look at the air pressure switch at the same time as the fan.

If there is a problem with the switch, they will be able to either fix the issue or quote you for a replacement.

  1. Printed Circuit Board

Your boiler’s printed circuit board (PCB) is the most important component in your boiler that links everything else together and keeps the whole thing working.

If any other component sends a signal that it has a problem, it is the PCB that will lock out your boiler and stop it from working.

But PCBs can go wrong too and if this component is the cause of the fault, it can be hard to work this out. The PCB can stop recognizing other components that have nothing wrong with them and generate fault codes that don’t actually reflect the real problem.

How to fix it:

It is highly unlikely that you will be able to diagnose a PCB fault yourself. Even your engineer might find it hard.

But an engineer will be able to test your PCB with a multimeter and this should identify any problems within the board.

Keep your fingers crossed that this isn’t the cause of your problem. If it is, you are looking at fixing or replacing one of the most expensive components in the boiler.

If you have an old boiler that is already out of warranty and has other issues, you would be wise to just buy a replacement boiler at this stage. In the long-run, this will save you money and if you buy from a site like Heatable you can get a brand new boiler at a bargain price.

  1. Radio Frequency (RF) Pairing

One fairly common issue with oil-powered boilers that tends to be overlooked is issues with the Radio Frequency pairing.

If your boiler appears to be doing what it wants and trying to fire up continuously, but not when you ask it to, this could well be the problem.

The good news is that this should be a simple issue to fix.

The Fix

To solve a problem with RF pairing, you will need to dig out your boiler manual. This should contain clear instructions on how to reset your thermostat to default settings. Follow these instructions and you should find the issue is resolved.

If you can’t find your boiler manual, search for the model online and you should be able to find either instructions for this task or an electronic version of the manual.

  1. Radio Frequency Crossover

If there are other houses on your street that have either got the same boiler as you or one that uses a similar RF system, you could end up falling victim to one of the slightly-less boiler oil boiler faults.

Most boilers run on a standard frequency and if your neighbours boiler is set to the same frequency, they can get crossed over. This means that your neighbours thermostat ends up controlling your boiler and vice-versa.

If you have found your heating is following a new pattern or your boiler is switching on and off at different times, this could well be the problem.

How to fix it:

The simplest way to solve the issue of radio frequency crossovers is to talk with your neighbours. If their thermostat is indeed set to the same frequency, it should take long to figure this out.

Your boiler manual should contain instructions on how to switch your boiler to a different frequency. One of you will need to do this. If you can’t find the instructions in the manual, a quick online search should again find the relevant information,

Buying a new boiler

If you find that your PCB or another major component in your boiler needs replacing, you will have a big decision to make. This type of fix is likely to set you back several hundred pounds and if your boiler is also old and inefficient, you might well decide it is not worth spending that sort of money just to keep it going for a few more months.

In that scenario, you are best to invest in a brand-new energy-efficient boiler. We recommend you get as many quotes as possible before doing this but one place you should definitely look is Heatable.

Heatable is an online installation company that offers some of the most competitive prices on a wide range of top-quality boilers. They have some great special deals too and will usually be able to better the price of regular national and local installers.


Oil-powered boilers are as susceptible to issues with firing up like any other type of boiler. In this guide, we have outlined eight of the most common causes of this issue and explained how to fix them.

Some of the fixes are DIY things that you will probably be able to do on your own. But others will require the help of a qualified engineer and could also cost your several hundred pounds in replacement parts.

Where this is the case, you may well want to consider buying a new boiler and we have recommended you check Heatable to get some of the best prices possible.

Has your oil-powered boiler had an issue with firing up? How did you fix the problem and did our guide help at all? Do you have any advice or tips that we have missed out in this guide? Any questions for us that we haven’t answered in this guide.

It is always helpful to hear the experience and advice of all our readers, so please do share yours with us using the comment box below.

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