Hi and thank you for using Just Answer.The thermo coupler is out. It is a sensor that lyes in line with the igniter/piliot light. Even though you get a start, the false reading is telling the valve something is wrong, or there is no flame. Replace this and you should be fine. If you have any other questions, please let me know.I wish you the best.Gary
Thank you. Do you know of any manuals on line etc?