Burner Not Firing? A Practical Troubleshooting Checklist for Plant Engineers

Every minute of burner downtime translates to lost production capacity. Before calling a technician, walk through this systematic troubleshooting checklist to diagnose and resolve the issue quickly.

Phase 1: Power and Safety Limit Checks (Before the fan spins) If the burner does not react at all when turned on: 1. Verify Main Power supply: Check for tripped MCBs, blown fuses, or single-phasing issues. 2. Check Controller Lockout: Is the reset button on the controller glowing red? Press it once to reset. 3. Check Safety Limits: Burners will not start if the control loop is open. Verify: - Is the boiler water level too low? (Water level electrodes lock out the system). - Is the steam pressure above the cut-off limit? - Is the temperature controller setpoint below the current water/oil temperature?

Phase 2: Pre-Purge Diagnostics (The fan spins, but no spark) If the blower motor starts, but the burner locks out after 10-30 seconds without a spark: 1. Air Pressure Switch Failure: The controller needs proof that the fan is blowing air. Check if the air switch is clicking. Verify the small silicone tube connecting the air duct to the pressure switch is not clogged or cracked. 2. Servo Motor Jam: On modulating burners, the servo motor (e.g. Siemens SQM) must open the air damper fully for pre-purging and return to the low-fire position before ignition. If the servo motor jams, the cycle stops.

Phase 3: Ignition Diagnostics (Spark clicks, but no flame) If you hear the high-voltage crackle of the ignition spark, but no flame ignites: 1. Fuel Supply Blocked: - For Oil Burners: Check if the fuel tank is empty, the suction valve is closed, or the Suntec pump has lost prime. Ensure the oil filter is clean. - For Gas Burners: Check the inlet gas pressure gauge. If pressure is too low, the gas pressure switch will block the solenoid valve from opening. 2. Solenoid Valve Failure: The solenoid coil (like Dungs, Brahma, or Lucifer) may be burned out. Test if the coil magnetizes when energized. 3. Electrode Alignment: If the spark is jumping to the diffuser plate rather than across the gap, it will not ignite the fuel spray. Ensure the gap is exactly 3-4mm.

Phase 4: Run Lockout (Flame ignites, but shuts down after 5 seconds) If the burner fires up, burns cleanly for a few seconds, and then shuts down: 1. Dirty Flame Sensor: The photocell (QRB) or UV sensor (QRA) cannot see the flame through a layer of soot or dust. Pull out the sensor and wipe the lens. 2. Incorrect Gas Ionization Current: If using an ionization rod, verify the rod is positioned in the hot flame core and has not oxidized. Check that the burner chassis is properly grounded. 3. Air-Fuel Ratio Misalignment: If the fan damper is open too far, the air blast will push the flame away, making it unstable and causing the sensor to lose track of it.