1.8t starting issue

[badrover]

My 2004 1.8t tourer auto has not been used for around 4 years but had been started periodically. It also has a dual fuel LPG conversion. I need to move the car soon so thought I'd check it out today. Initially the car wouldn't start. I checked for a spark and all was good but it just wouldn't fire. The LPG setup is pretty standard, starts on petrol until a predetermined temperature is reached when it flicks over to gas. This can be overridden though so that the car will start on gas. Having done the override procedure, it fired up an ran very well on gas except that it would only idle and would instantly cut out of I attempted to rev it. Once the car was up to temp I tried to flick back to petrol and it just cut out. I can't hear a fuel pump kick in from the petrol filler neck so could it be a failed fuel pump?