Bleeding an oil furnace after a run-out: what it is, who should do it
Updated 2026-06-11 · In progress — full guide arrives before the heating season
Quick answer
After a run-out, air in the fuel line keeps the burner from firing even with oil in the tank. Clearing it means purging air at the pump's bleed port while the burner runs — a procedure with pressurized fuel spray and lockout cycling involved. If your burner's owner manual documents it, follow the manual exactly; otherwise this is a quick, inexpensive technician visit, often free with the delivery.
Why the burner won’t fire even though the tank is full again
- Single-pipe systems airlock after a dry run; the pump can’t self-prime against air. Two-pipe/Tigerloop systems usually self-purge — how to tell which you have (look, don’t touch).
What the bleed procedure actually involves
- Described in plain language: bleed fitting on the fuel unit, a clear tube to a container, running the burner until oil runs clear and air-free, within the control’s trial timing. Pressurized spray + repeated lockout cycling is the hazard pair.
The honest boundary
- If the manufacturer’s owner documentation for YOUR burner includes a bleed procedure: that document is the authority — follow it exactly, with eye protection and rags staged. If it doesn’t, the manufacturer made that call deliberately; book the tech. Restate one-reset rule for the attempts.
What the tech does beyond the bleed
- Filter and strainer check (run-outs drag sludge), nozzle check if lockouts stacked up, leak check at the fitting afterward.
Cost and timing
- Often bundled free with an emergency delivery; standalone price band; why “prime included” is worth asking for when ordering.
Avoiding the next one
- Same prevention block as the run-out guide (stick weekly, auto-delivery).
Sources
- Suntec / Danfoss fuel unit (oil pump) documentation
- R.W. Beckett burner owner-information sheets