The fuel pump, an automotive part, is used to transfer the fuel from the tank to the engine injection systems. This pump consists of an electric motor driving a turbine: this induces the fuel flow. The current flow is realized between the stator and the rotor thanks to the friction of two fixed brushes against a slip ring. All elements are made of graphite/polymer composites and are immersed into fuel. The aim of this work is to contribute to the understanding of immersed electrical sliding contacts. A specific tribometer was developed in order to mimic the fuel pump. It allows simultaneous measurement of friction forces, wear and electrical contact resistance for various mechanical, electrical and physicochemical conditions. New carbonaceous materials, specifically designed for new biofuel, exhibited different tribological behaviour. The wear observed is mainly due to the current flow, electrical arcs in particular, which modifies the surface topography. Two kinds of damage were depicted: craters and bumps whose volume increases with the arc-produced energy as a function of the presence of polymer at the vicinity of the surface. Issued from these experimental results, a phenomenological model of the wear behaviour was proposed. It brings new insights into the complex and numerous mechanisms occurring during the friction of the brushes and commutator.
