The igniter will ignite the gas, and the gas will run for a second or a few seconds and will then cut off. It will continue to cycle like this until it finally will stay on but at times will take forever.

Flame senser,, find it,remove clean real good with very fine steelwool,replace,let us know how it works


Goodluck

wmproop is correct, yet again. Sure sounds as simple as a dirty flame senser.