R44 Raven II engine shutoff when overfilled with gas?

[Benson Milam]

I have worked around R44 Raven II's for a year or so now and am also a lineman at our airport, so hot fueling helicopters is not a rare occurrence for me. Several months ago while fueling our R44 Raven II the fuel pump got momentarily jammed, causing me to overfill the auxiliary tank. When that happened I noticed the engine bogged down for a second but the pilot quickly fixed the problem and kept the engine running, since that day I haven't even thought about it. Today I was teaching our new lineman how to hot fuel the R44. I made him watch me as I filled the main tank so he would be able to fill the aux tank by himself. As he started to pump I noticed he was pumping way faster than needed, before I could say it and catch his mistake it was too late. Gas was everywhere. The engine bogged down and the pilot did nothing to correct it, therefore the engine shut down. What causes this? I have read the POH and looked at the fuel tank diagram to see if there is a sensor or if the vent gets full and doesn't allow airflow. Can't seem to find any answers on this. Y'all have any??

[sidegrip]

If filling the AUX tank. Maybe gas fumes got sucked into the air intake causing a over rich mixture that may have caused the engine to stumble