1990 300SE Auto Engine cuts out

[lepton]

The car has a recent LPG conversion and the engine has started cutting out while turning sharp left hand bends. It has always started up again when placed in park but now won't even do that. The AA checked it and said that the spark was OK and the fuel pump was working though seemed to be running too fast. The car fires healthily for half a second then dies regardless whether switched to fuel or gas. I would be grateful if anyone has any ideas.

 

[lepton]

Problem Solved

The vacuum pipe to the idle valve had a slight crack which opened up when the engine moved. This let in enough air to cut the engine.
Thanks for looking at the problem - lepton.