Diagnostic systems and methods for variable lift mechanisms of engine systems having a camshaft driven fuel pump

A lift mechanism diagnostic system comprises a fuel pump disabling module, a pressure module, and a diagnostic module. The fuel pump disabling module selectively disables a fuel pump that is driven by a camshaft. The pressure module determines a first pressure of fluid provided to a variable valve lift mechanism when the variable valve lift mechanism is operated in a first lift mode while the fuel pump is disabled and determines a second pressure of the fluid when the variable valve lift mechanism is operated in a second lift mode while the fuel pump is disabled. The diagnostic module selectively diagnoses a fault in the variable valve lift mechanism based on the first and second pressures.