An oil boiler that will not fire can be frustrating, but the safest approach is to rule out simple controls first and then avoid repeated resets.

Key points

  • Check power, oil level and controls first.
  • A burner that tries to start then stops needs diagnosis.
  • Clicking, smell of oil or repeated lockout should not be ignored.
  • Oil burner faults are often connected, not isolated.

Safe checks at home

Check the oil tank level, isolation switch, fused spur, programmer, room thermostat and any lockout light. Make sure the heating controls are actually calling for heat.

If the boiler has an external fire valve or visible isolation valve, check that nothing obvious has been switched off. Do not remove burner covers or dismantle parts.

What the starting sequence tells you

If the burner is silent, the issue may be power, controls or safety interlocks. If it runs briefly, clicks or locks out, the fault may involve ignition, oil supply, photocell signal or combustion.

A boiler that smells of oil or smokes should be left off until it has been checked.

Common causes

Common causes include air in the oil line, blocked filters, failed ignition parts, pump issues, a dirty or failed photocell, blocked nozzle, poor burner setup or a controls fault.

Changing parts without testing can waste money, especially where poor combustion or oil supply is the real reason a part appears to fail.

When to book fault finding

Book a fault check if the boiler will not recover after simple checks, locks out more than once, starts unreliably or has become noisy, smoky or smelly.

Useful details to send are the boiler make, model, fault lights, when the problem started and whether you still have heating or hot water.

Common questions

Why does my oil boiler click but not fire?

Clicking can point to an ignition attempt, but the cause may still be oil supply, electrodes, transformer, nozzle, photocell or burner setup.

Is it safe to keep trying?

No. If the boiler repeatedly fails to fire or locks out, stop trying and arrange a proper fault check.