Cause 1
Igniter
The igniter is the most commonly defective part for a gas oven that won't turn on. The igniter has two main functions. First, the igniter draws electrical current through the oven safety valve to open it. Second, the igniter gets hot enough to glow and ignite the gas in the burner assembly. If the igniter gets weak, it will fail to open the safety valve correctly. If the valve does not open, the oven will not heat. To determine if the igniter is defective, observe the igniter when the oven is on. If the igniter glows for more than 90 seconds without igniting the gas flame, this indicates that the igniter is too weak to open the valve. If the igniter is weak, replace it. If the igniter does not glow at all, use a multimeter to test the igniter for continuity. If the igniter does not have continuity, replace it.
Cause 2
Bake or Broil Spark Electrode
For bake & broil burner ignition an oven burner spark electrode is used to ignite the gas. The electrode is a device that sits right next to the burner. It functions like a spark plug. As power is applied to it a spark jumps from the spark electrode tip to the to the electrode shield, igniting the gas. If the electrode is broken or worn out the spark may not occur. Visually inspect the electrode assembly for cracks in the porcelain housing or damage to the electrode tip itself. Be aware that a proper ground and the correct polarity of the incoming voltage to the range is necessary for the electrode control to sense the presence of a flame once the burner is ignited. If the burner goes off after ignition check for proper ground and the correct polarity at the wall outlet.