I am having a hell of a problem with my 1990 745 (B200F engine) and am wondering if anyone knows what is wrong with it.

The engine cut out whilst I was half a mile from work yesterday and wouldn't even turn over when I tried to restart it, as it would if the car had a dead battery (The battery is thre weeks old and the rest of the electrics are fine). I left it for ten minutes whilst I called th AA and it started again with no problems. I got to within 100yds of work and it cut out again. However, after ten or so minutes it started, but stopped again after five minutes and wouldn't turn over.

I find that every time I start the car it will only run for about 5 minutes before it stops and will not turn over, as it did when it first conked out. It always restarts after ten but will stop after five. The AA said that the alternator wasn't showing any output (Their test rig showed this- They couldn't replace the alternator due to being unable to get one as it was Sunday evening), but a spares shop says that this wouldn't cause this problem as the battery would just go completely flat and the car wouldn't resatart at all. They reckon the coil is faulty.

I cannot fathom out the problem and I am getting REALLY upset as I have no other means of transport and need the car for work. I can't see the alternator giving this sort of problem as I have never come across trouble like this before. I have heard that faulty coils can create short running problems. But who knows?

Your input would be really appreciated!
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