In fact the fuel pump in that instance had not been left on during flight, it had been turned on to switch tanks as per the poh and then turned off again. It was some short time after turning off the pump that the cabin filled with smoke.
I have an electronic aux fuel pump. I turn it on during startup. I turn it off again immediatly after startup. In fact my hand goes from the starter button to the fuel pump switch as I check for oil pressure, which is first thing I do after startup.
The next time I turn it on is the next time I start the motor.