V 70 l – engine goes off while driving.

Hello, my vehicle: V70 L ,140hp. 2,5l, BJ:2000, vehicle IdentNr:YV1LW65F…… LPG For some time the car has been running out during the ride. It mainly happens when it is driven a longer distance. At first all the lamps flash, then it goes out and does not start. After 20 minutes you can start it again. The fuel pump relay has been replaced. It can not be because I drive on gas. A person at the tank said it could be a mistake in the control unit. The error memory says nothing. Does anyone have a tip? Greeting Jürgen