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Sorry about the abrupt message Paul, I was using the works computer.
I now have the broken pretensioner in my possession, it's not a pretty sight.
There's an extremely strong spring housed behind the pretensioner wheel, the end of the spring sticks through a 'latch' on the casing, this casing appears to have fractured, the end of spring has then popped up (because it's no longer in the right place or under any tension) and jammed itself into the plastic teeth of the pretensioner wheel itself.
The plastic has shattered and the cambelt has then loosened, causing major mayhem.
So I now have an extremely broken pretensioner, a perfectly OK cambelt (no wear, 62,000 miles), a bill for £1200.00 because all 16 valves are bent, a deeply pissed off wife, who may kill.
PS You can't get major engine work done on your FIAT because it requires special tooling (for each engine) and FIAT won't lend or sell you the tool.
If everyone's engine has this same pretensioner problem then I think we should do something about it!