My motorhome won't start

Just an update. Our motorhome was towed to a main dealer. Although they did get it started (without using a key!), it filled the workshop with dark smoke. They think the engine must have got flooded at some point and perhaps a solenoid is stuck open. We are not much further forward. We have decided enough is enough and we are changing the motorhome for another (second hand, of course) one.

If we do find out what the problem is, I will post again.

Thank you all again for your ideas and suggestions. It is great to have such a supportive group.

Has the garage checked the fuel filter and housing?  If not suggest they very carefully change the filter element and seal using only genuine Fiat replacement parts.  Alternatively replace the whole filter housing but that is the expensive option.  After market parts should not be used.