Oven will not preheat. Pulses on an off.

Turned off the gas. Disconnected gas inlet, burner supply line and oven supply line from regulator. Unscrewed regulator from its bracket. Replaced with new regulator in reverse order and added teflon tape suitable for gas lines to all threads.

Unfortunately, the regulator was not the cause of the problem and the oven still does not prehead - acts exactly the same.