My dad aquired a PC-9 arf with a Evolution 40 motor ( mounted upside down) that was put together and were told it had been flown.

We went to run it and it would run for about a minute and then suddenly stop. The setup of the tank is a bit different as the fellow who installed it used the nipple above the stopper for the vent.??? and capped off 2 of the stopper lines.

Any thoughts. We were going to start by replacing the tank and see if that helps.

Del