An apparatus for testing a fuel cap includes a gas manifold, a fuel cap connector, a base, and a removable cover. The gas manifold is configured to provide a bidirectional flow path through the fuel cap. The fuel cap connector is integrated with or coupled to the gas manifold, and the fuel cap connector is configured to connect the fuel cap to the gas manifold. The base is configured to support the gas manifold and provide at least a first gas input to the gas manifold and through the fuel cap via the bidirectional flow path. The removable cover is configured to be removably connected to the gas manifold and provide at least a second gas input to the gas manifold and through the fuel cap via the bidirectional flow path.