Boiler Won't Fire Up
The controls call for heat, the pump may hum, but the burner never lights and nothing gets warm..
The controls call for heat, the pump may hum, but the burner never lights and nothing gets warm.
What is actually going on
The controls call for heat, the pump may hum, but the burner never lights and nothing gets warm.
The realistic causes, in order
No gas at the appliance — a closed isolation valve, a prepayment meter that has run out, or an emergency control valve knocked shut during other work Ignition failure at the electrode: a cracked ceramic, carbon build-up on the tip, or an electrode gap that has drifted outside the manufacturer's setting A flame supervision fault where the ionisation probe never confirms flame, so the gas valve shuts down within seconds as designed
What we test on site
Gas working pressure and standing pressure at the appliance test point, with all other gas appliances running Spark quality and electrode condition, plus the earth path the ionisation signal relies on Gas valve operation and the boiler's own fault history stored on the PCB
Worth checking today if you have a boiler that won't fire up
- Check other gas appliances — if the hob won't light either, the problem is the gas supply, not the boiler
- Confirm the boiler has power and the display is showing something, not blank
- If you can smell gas at any point, do not touch electrical switches. Leave the property and call the National Gas Emergency Service on 0800 111 999. Only a Gas Safe registered engineer may work on the gas side of the appliance.
Who does the work
- Gas Safe registered engineers — registration 554328
- Worcester Bosch accredited installer
- John The Plumb Ltd, company registration 10026483
Get a boiler that won't fire up diagnosed properly
Most no-ignition faults are resolved at component level — electrode, gas valve or PCB — rather than needing a replacement boiler.
Questions we get asked
What causes a boiler that won't fire up on a gas boiler?
No gas at the appliance — a closed isolation valve, a prepayment meter that has run out, or an emergency control valve knocked shut during other work
What normally puts a boiler that won't fire up right?
Most no-ignition faults are resolved at component level — electrode, gas valve or PCB — rather than needing a replacement boiler.
Is it safe to keep using the system with a boiler that won't fire up?
If you can smell gas at any point, do not touch electrical switches. Leave the property and call the National Gas Emergency Service on 0800 111 999. Only a Gas Safe registered engineer may work on the gas side of the appliance.