Ignition failure
-No gas pressure.
-Gas pressure under minimum value shown on rating plate.
-Gas line not completely purged of air.
-Defective Electrode.
-Loose burner ground connection.
-Defective Ignition Cable.
-Defective gas valve (check for 24 Vac at harness during trial for ignition before replacing valve).
-Air-fuel mixture out of adjustment - consult factory.