Most of the time, when a gas burner refuses to light or runs poorly when lit, the cause is dirt or grease. Fine particles of dirt or grease spatters can clog the flame openings on the burner, or can plug the pilot light that starts the burner. Here's how to handle both problems.
Turn off the gas to the stove. Lift the cooktop so you can access the burner parts. On some stoves, you just need to lift the corners to raise the cooktop; on others you have to push the top backward first, then lift. Prop the cooktop open, using the brace that is attached to the inside of it.
Remove the burner unit by lifting up the back end of the unit and sliding the front end off the gas-supply lines.
Wash the burner unit in warm, soapy water, using a scrub brush to remove any grease that may be blocking the openings. Let the unit dry upside down in a dish rack before moving to step 4.
Clear the flame openings, using a straight pin or needle to poke out any dirt or debris (see A).
Clear the flash tube openings, using a needle or piece of fine wire, such as one strand from a piece of twisted electrical wire.
Clean the pilot opening, using a straight pin or needle (see B). Take care not to enlarge the opening. If you do, the pilot may not run right.
Reinstall the parts, turn on the gas to the stove, and relight the pilot light with a match. Test the burner.