US Patent 9840985 Fuel vapor line diagnostics

Methods and systems are provided for diagnosing fuel vapor leaks due to un-latching of quick connectors in interfaces of a fuel vapor system. In one example, a method may include using positive pressure generated in the intake manifold by reverse rotation of the engine unfueled, to detect un-latching of quick connectors in the fuel vapor system. After the positive pressure test, a negative pressure test is performed on the fuel vapor system to confirm any un-latching of quick connectors.