I have a Suburban 6-gallon water heater. It had a sporadic problem last year and it seems to be permanent now. I can light the pilot light without any trouble, but when it's time to heat water, the gas comes on and then nothing happens for a few seconds and then I can smell gas. Soon after that, there's a whoosh of flame and then the burner and pilot light are off. I have relit the pilot light several times and tried again but the same thing happens. I've cleaned out the burner tube and orfice. Does anyone have any other ideas? Thanks.