The field equations for cylindrically symmetric perfect fluid models with a non-scale invariant equation of state where the energy density is linearly related to the pressure are rewritten as a set of first order coupled ordinary differential equations. Variables are chosen such that the resulting phase space is compact and everywhere regular. The dynamical systems approach, used in the past mainly for scale invariant matter sources, is subsequently used to gain qualitative information about the space of solutions. It leads to a simple way of demonstrating the existence and properties of interior sources for cylindrically symmetric vacuum solutions. The models are shown to exhibit asymptotic scale invariance.