Water heater problems with a pop up camper?

I have a Viking camper and the pilot lite will not stay lit. I lite it as you are suppose to and when you release the pilot button the pilot will go out. It lites every time, but wont stay lit. I've replaced the thermo coupler, but that didn't make any difference and I'm not wanting to replace the control vale due to the cost. Is there anything else that could be th problem.