RE: What causes a P120 to Flame Out
White smoke is generally a positive indication of air in the lines.The whitevapor is caused by the pump continuing to push fuel into the engine after the fire has gone out. The GSU most likely would have said Fuel Fail which is pretty much a catch all for any engine failure not directly related to something it actually measures. The shutdown rpm's, temps, etc. don't mean much since they were recorded long after the engine quit when the ECU finally gave up and turned everything off.
So, there is an air leak between the pickup on the tank before the UAT and the engine festo plus there's no real reason to think the pump or data cable is bad - although data cables can be problematical. But that just means the solenoid would have shut off with no smoke.
Likely causes:
Air bubble in the silver filter. Funny, but I've seen flameouts due to this as long as 6 flights after a fuel purge or reinstallation. Shake them good with the filter in a vertical orientation to clear the air. Purge the lines and filter after any flame out. I usually run the pump test voltage up to around 2 volts, or higher, 4 or 5 times shaking the filtervigorously to do this.
Fill line into UAT not sealed - leaking plug or valve. Eventually results in an emtpy UAT and a flameout. Was the UAT empty??
Festos in the fuel lines, either before or after the pump. First glance says they should only suck air on the suction side (tank/UAT side) of the pump, but I have seen festos in the lines on the pressure side cause problems - including the one on the front of the engine. All the guys I fly with on a regular basis have had trouble with festos in the fuel lines and don't use them anymore. The fuel lines can take a bit of a set or get a little stiff after a lot of fuel has passed thru. I occasionally cut back the fuel line at the engine festo to give it a fresh seal as sometimesa little movement in the line there can let air pass.
Connections not safety wired. Use .015 or .020 wire to double wrap all connections and seal them.