Grill igniters

Igniters have heavy wear inside a gas grill. Because these miniature "spark plugs" must be located on or at the burner they are in the fire when the gas grill is in operation. As the grounding surface of the burner becomes coated with grease and residue, the porcelain insulator on the electrode can crack from the heat. If this occurs, the spark being transferred through the insulator will "bleed" from the crack, and ignition will occur only after a build-up of gas or not at all. For safety reason, igniters should be replaced when this occurs, and burner surfaces cleaned up in the igniter area. Burner portholes in this area should be kept clean and open. The spark gap between electrode and burner is about 3/16".
An igniter sends a high voltage along the wire to the igniter electrode inside the collector box. The collector box collects gas which sparks the light.

If your grill has an igniter that no longer works:

Check the connections at the push button itself, and at the spark collector box. These connections can become corroded.

Now check the insulator in the collector box for cracks. Cracks collect moisture and reduce the spark, in which case will require replacement

Sand electrode tip inside the collector box
Clean electrode with alcohol
Lightly sand the inner roof of the collector box
If this information did not help you fix your igniter, replacement will be necessary.