Hi,
I have Fiat Ducato panel van motorhome, 2004, 2.8 engine

I switch on, wait for the glow plug light to go out, then turn the key.
The engine turns over at a good speed but the engine doed not start.
I switch off and repeat the procedure and the engine will fire up
normally.
If I stop for a short period, say getting fuel, the engine will start
first turn of the key.

My Fiat Dealer says it could be the rpm sensor, phase sensor, ecu.....

Any ideas

Peter