I believe there are a number of small diesel engines under evaluation at the present, all using jet fuel and not the smelly stuff used by cars. The cost and environmental problems of conventional avgas 100LL seem to be driving the many projects.
See Cirrus Design who are set to use a turbodiesel engine by a French offshoot of Renault, SMA.
www.cirrusdesign.com
SMA have website
www.smaengines.com
There is a British company called Wilksh, but I'm not sure of the spelling! They are based in Milton Keynes and have had their engine under test in a number of airframes.
Also, I remember seeing a homebuilt recently from Germany that had a modified Isuzu turbdiesel from an Opel Corsa.
Hope this points you in the right direction.