Let's not forget the possibility of fuel foaming, which will do just what Cougar described, i.e., run fine on the ground, but run sour, or quit, in the air.

The fuel tank, including the neck and metal tubing feed lines from the tank, must be completely isolated from any hard part of the model. Any hard part of the model, including the firewall.

Engines do not cop an attitude. They are inert lumps of metal. They do not "know" anything. For instance, where they are. If the conditions remain favorable, they will continue to run. If they do not, one must determine which condition changed in an unfavorable manner and why.

I would really ensure that the engine's fuel supply is not foaming the fuel first. Make sure there are no air leaks and that the clunk in the fuel tank is not so close to the back of the fuel tank that it can be suctioned to the rear wall of the tank, cutting off the flow of fuel. Ditto the vent line tubing inside of the fuel tank. It too can be pulled against the fuel tank wall and can cut off the outside air that is needed to permit the fuel to flow to the engine. Sometimes, when things "look okay", but the problem persists, it is necessary to just try something. Especially when it comes to internal fuel tank feed line length. Cut a 1/4" off of that feedline, just to be sure. Sometimes we cannot imagine how a fuel line can stretch far enough to block off the fuel flow, but it does.

Good luck solving your problem. Let us know what the solution was, when you find it.


Ed Cregger


edited by moderator