harry-homeowner
The first thing you do is a visual test. Turn the oven thermostat on, wait at least 30 seconds and take a look at the igniter. It should glow very bright red, almost close to white. Normal time for the igniter to open the gas burner valve and to light up the burner is between 40 second to 1 minute. If it glows red but not bright and even if it does light up the burner but it takes more than a minute, the igniter is bad and has to be replaced. If it does not glow at all, remove the power from the oven, remove the igniter wires and check for continuity between these wires. If there is no continuity, replace the igniter. The part number for the new igniter is AP3129373
If the igniter is not the issue let me know and we will proceed with further diagnosis.
Just for your references here is the break down diagrams for Whirlpool range Model SF303PEKQ0
Good luck.
Gene.