well i've been told to always start on petrol and after a few minutes switch to gas when the engine has warmed up. Why would the engine go bang?
if you keep running it on gas its takes all the carbon out the enegine which makes it run even hotter , lpg runs hot and burns all the cardon out so it looks like brand new inside wich is not good ,
my lpg transit had 190k on the clock befour i sold it , they are good for the miles if looked after , also you need to change the way you drive as well with them