Technical Ducato Immobiliser Problem

[FiatRapidoman]

Hi there, new to this forum, and I am hopeful you can offer some help please! I have a Rapido motorhome, based on a Fiat X244 2.8litre chassis cowl, registered in June 2006. It has covered 33k miles, reliably, other than this problem; After a fastish run of 120 miles, we stopped for less than 5 minutes in a lay-by. On attempting to re-start, ignition as normal, but nothing happened. The binnacle lights all appeared as normal, and the 'padlock' immobiliser lit, and went out. The starter did not turn. Over the next ten minutes I tried the spare key (both are black 'flick keys') to no avail. Took off battery earth lead, and replaced, to no avail. Called Green Flag, and 'van started on first attempt! This was 1hr 40mins after the original stoppage. They said 'no fault found'
Decided to carry on journey, as it was the first day of our holiday. Ran a further 150miles, stopped for diesel, vehicle failed to start on forecourt. Sat for twenty minutes, and van started as normal. Perhaps should add, that after this failure to start, I had removed the keys from the ignition, and after the twenty minutes, re incerted, and started.
For the rest of the two week holiday - every time I stopped, I took the keys out, and every time I replaced them, the van started. On the way home - just once -I forgot, and after a two minute stop (honestly), keys still in ignition, van failed to start. Removed keys, had lunch, replaced keys, van started! So, what is the problem? Please, would much appreciate any advice. Many thanks, John.:worship:

 

[Most Easterly Pandas]

You haven't any other vehicle keys on the same keyring have you?

 

[moodrater]

Not the immobiliser because the engine still turns over even with immobiliser active and as you say the immobiliser light is off, is they key actually turning fully to the start position there is a plastic latch in the lock to prevent you reengaging the starter until you switch the ignition right off. The central pin in the ignition can come loose causing the ignition to jam.

 

[FiatRapidoman]

Thank you Most Easterly Pandas - but there are no other keys on fob.
Thanks also to 'moodrater' - I had not 'twigged' that the starter motor would run even if the immobiliser was active, and that therefore this IS NOT an immobiliser problem. I have to say that I thought that the key was turning just 'as normal', but will only know when the fault re appears. Is there any other way of checking? Many thanks so far.