Hey answered you on Youtube.
I've got the same car...same yearwith LPG. You saw the
video on Youtube
This is a common issue withe 120hp T-jet.
In my case, i have replaced/tested investigated..etc ALL tings:spark plugs, fuel pressure, some tested the intake, temperature sensors, compression...etc. ALL were perfect/in good working order.
The only thing that works 100% of the time every time is, finishing the petrol i have in the tank, and then add new petrol. Then it will start 100% perfect for a few days.
New petrol make all the difference.
But because i also have LPG i run the car on LPG for most of the time after start. I assume the petrol rapidly ages/degrades in the tank/fuel rails from repeated heating from the engine.
The problem is only more evident on cars with LPG, because the petrol spends 20-40x time more in the tank, than a car you would be running only on petrol.
I have made a small circuit with a 555 ic, some mosfets, a few caps, resistors and a button.(search for 555 monostable)
When i press that button the car's injectors open for ~1/4 second(adjustable).... this squirts out some fuel in the intake.
With the additional fuel in the intake it now starts every time even if the petrol in the tank is older than 2 moths. (it can still stumble a bit.. but in 20 seconds it's good to go).
You can test by adding some starting fluid in the in take before cranking 100% it will start first time.
Stop wasting money replacing the spark plugs every 20k km. do it every 30k as Fiat intended. Make sure you sue the recommended spark plugs.(mandatory expensive iridium spark plugs fro the t-jet).