Try the fuel first. Get some good 10% - 15% nitro fuel. There are several on the market. Wildcat and Omega are my favorites, but there are others as well. If you have a fuel filter in the line between the tank and the carb, get rid of it and filter the fuel between the fuel jug and the tank. If that does not do it try a new RC long glow plug. If that does not work, I suggest you send it in for service.