Lpg problem

[A8 Owner]

Half a mile if that from home the car died on me Steve thought it was the geeeeaaarrrbox prob as car just came to a stop. Steve quickly tryed a few things out at side of Rd. He found problem just doesnt know what to do about it yet, its the LPG it wont run on it. flick to petrol got us home. Steve has checked some sites that say check your water level and so on but there all fine, cant be the injectors as there r none working we think as it doesnt run. What we both dont understand is tho the system is set on auto. When the engine gets warn it goes onto LPG, we got told if it ran out of LPG it will auto turn to petrol. So if it does this why is it when it wont run on LPG it doesnt just auto swop to petrol. Going to leave it over night and see if it runs when cold and changes to LPG.

ANY IDEAS ANYONE