When lighting the burners on the stove top, it takes, it seems, forever for the gas to start flowing. The ignition spark is strong but the gas doesn't start to flow for maybe 15 to 30 seconds. When the gas starts to flow you can hear it. After the burners are lighted, everything works normal. It's like a gas control valve just suddenly opens after a long wait. Any suggestions on what the problem might be would be appreciated. The oven works like it's supposed to. No problem with that part.