An engine ground system for increasing the potential of an engine. This is an engine ground system wherein intermediate portions of a ground wire one end of which is electrically connected to the negative electrode terminal of a battery are electrically connected to engine ground points and the other end of the ground wire is grounded to the car body. The engine ground points can be an engine cylinder head, an intake manifold clamping member, a cylinder head cover, and a throttle body (7b). Further, a plug cap ground wire is connected between the plug cap clamping member and the intake manifold clamping member.