mk 3 fiesta xr2i wont turn off with key any ideas?

my 1993 mk 3 xr2i did have a starting fault so i have removed the imobiliser it now starts first time every time but wen i turn the ignition off the engine keeps running untill it has drained the battery below starting charge i have also changed the ignition switch has anyone got any suggest if so will be greatly appreciated

rich
February 2009