Teba cooker 2001/2

has grill and oven in same oven compartment.
Grill burner on top. Oven burner at bottom.
To light (with match), the gas knob has to be PUSHED, light, and let-go.
But when knob is let-go, oven burner will not stay alight.
Would be grateful for info on how to make it stay alight.

Louis, March 2011