The heater has flamed out, but I was not there when it happened. The flame outs are not frequent enough for me to be there when they happen.
This is a difficult problem to diagnose. The problem could be within the heater, or it could have something to do with the fuel system leading up to the heater. To determine which of these is the problem, the heater should be run from a separate fuel can.
Clamp off and disconnect the fuel return line.
Connect a 3 foot piece of 1/4″ fuel line (or 1/4″ clear hose to get more information) to the fuel return fitting on the heater. Place the end of this fuel line into a fuel container.
Clamp off and disconnect the fuel line going to the fuel inlet of the heater.
Connect a 3 foot 1/4″ fuel line (or 1/4″ clear hose to get more information) to the fuel inlet fitting on the heater and place the other end in the fuel container. Make sure there is enough fuel in the fuel container so the end of the hose is submerged in fuel.
The fuel in the fuel container should be completely clean, or an in-line fuel filter should be placed on the end of the 3 foot fuel line that is placed in the fuel container. If any debris is drawn into the fuel line, it will lead to additional problems.
Press the reset button on the front of the heater and allow the burner to fire and run long enough to determine if it is going to flame out. You may need to run the heater off the fuel can for more than a day, so make sure you use at least a 5 gallon fuel can and keep the fuel level above the 1/4 mark.