A fuel system comprises a fuel tank including at least a top wall, a bottom wall, and one or more stanchions positioned within the fuel tank, each stanchion coupled to the top wall and the bottom wall. A strain gauge is positioned on the outside of the fuel tank, opposite an intersection of a stanchion and the top wall, such that degradation of the stanchion results in results in pressure-dependent deformation of the fuel tank that is registered by the strain gauge. In this way, degradation of deformable fuel tanks, such as polymeric fuel tanks, may be diagnosed and indicated.