1991 90 10v problems

[Rick Hayllar]

Hi all
I am having fun!! and at the same time getting frustrated restoring this 
be beast.
It has had a replacement and runs well (uses no oil), apart from being 
very thirsty. It never seems to reach operating temperature. I suspected 
the thermostat was stuck open but it is not.  So something is telling 
the system that it needs to keep the mixture rich?  So any good ideas 
are welcome.
rick hayllar