Re: 1999 166 2.5 V6 won't start
The only thing I can comment on is the smell of fuel.
I had a fuel smell coming from my 166 the other day. Upon investigation I tracked the smell to the left hand side of the fuel rail. Brushed my finger underneath the joint that joins the fuel line to the fuel rail and there were some traces of fuel there.
Basically, the washers either side of this joint had gone hard over the years (copper washers) and wasn't forming a proper seal. I had these replaced and hey presto, leak gone and smell of petrol gone. It is easy to do, but be careful as the pressure in that rail will spray fuel out !!
I'm not saying this is the same source for your smell, but it may be worth a look, just in case.
Alfa 166 3.0 Sportronic