The water heater in our 2001 Coleman Utah won't stay running. I light the pilot just fine, but when I turn it to 'On' it runs for about 20-30 seconds and then flames out. It spills out gas until the thermo-couple cools down. I pulled out the burner assembly and brushed out the main tube, cleaned the pilot burner and thermo-couple and blew it all out with an air compressor. Still no luck. I've been through some posts here and other places and can't figure out what else to try. The pilot flame and main flame look pretty good to me when they are running, though the force of the gas running into the burner seems kind of high. Any suggestions?