State the burner, the normal lighting sequence used and whether the flame ever established properly. Do not defeat the control to keep gas flowing.
What the observation means
Some burners require a model-specific hold period during ignition, but persistent failure after the approved procedure needs assessment. A generic timing rule is not appropriate for every cooker.
A useful next step
Stop repeated attempts and follow the manual's waiting and safety directions. If gas is smelled, contact the emergency service from a safe place. Do not wedge the knob inward or attempt internal adjustment to bypass a flame-safety function.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.