GW Vir variables are the pulsating members in the spectroscopic class of the PG 1159 stars. In order to understand the characteristic differences between pulsating and non-pulsating PG1159 stars, we analyse FUSE spectra of eleven objects, of which six are pulsating, by means of state-of-the-art NLTE model atmospheres. The numerous metal lines in the FUV spectra of these stars allow a precise de...