loss of power

hi I have a 2001 p38 diesel its the second one I have had of the same year the first had 186k on the clock and in truth was a bit of a dog.The current one has 116k on the clock both cars had similar fault which only occurred now and again. the symptoms are that when going downhill the car completely shuts down the engine stops and no power steering i come to a stop put the car into park and the car restarts immediately.
Does any one know what this is - is it fuel starvation. It only happens going down hill but I am worried it may happen when i am in the outside lane of a motorway.

Is this an automatic? First of all check for air in the clear pipe from filter to injection pump. If none. If the Mil lamp flicks on coming off cruise control it is an injection pump problem. Get it on diag and i think you will find it has a fuel quantity control fault. Possible a worn pot on the fuel quantity servo. Re-conned pump needed.

Might be worth doing the lift-pump check. You never know and it is WAY cheaper than the FIP. Unfortunately Wammers is usually right.

Thanks to both will let you know how I get on