A grounded fuel tank assembly includes a non-metallic fuel tank having a container and a hollow filler neck, a fuel cap with a hollow stem, and an electrically conductive insert member. The insert member includes a hollow sleeve which is received by the neck, an annular frusto-conical first ring which is joined to an end of the sleeve, and a second ring which extends away from the first ring and which at least partially surrounds a portion of the neck. The sleeve has internal and external sleeve threads formed thereon. The internal sleeve threads engages external cap threads, and the external sleeve threads engages internal neck threads. An electrically conductive ground strap is exterior to the container and engages the second ring. The insert includes tabs which engage the neck to prevent rotation of the insert.