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Puff-back / delayed ignition
What is going on
Possible causes and checks for: puff-back / delayed ignition.
Likely causes
- Water in oil
- Electrodes mispositioned/loose
- Carbonized insulators
- Bad nozzle
- Voltage drop at start
- Pressure wrong
- Transformer leads loose/dirty or transformer weak
- Excessive air/high draft
- Spray pattern distorted away from electrodes
- Air in fuel line
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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.