I was thinking about that if the pump's purpose is to actually cool the oil
(for the sake of the turbo) then maybe it is controlled by an oil temp sender
instead of a coolant temp sender.  Maybe one in the vicinity of the turbo?
Just shooting in the dark here as I have never seen a stock turbo diesel
setup before (we never had them here in the states).  I have seen a few nice
conversions though.

Thanks,
Ken Wilford
http://www.vanagain.com
John 3:16
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