A diagnostic system for a vehicle includes a purge valve control module that closes a purge valve. The purge valve regulates fuel vapor flow from a fuel vapor canister to an intake system of an engine. A pump control module, after the closing of the purge valve, turns on a pump that pumps fuel vapor toward the purge valve. A first pressure module, after the purge valve is closed, determines a first pressure measured using a pressure sensor located between the pump and the purge valve. A second pressure module, after the determination of the first pressure and while the pump is on, determines a second pressure measured using the pressure sensor located between the pump and the purge valve. A diagnostic module selectively diagnoses detachment of the purge valve from the intake system based on the first and second pressures.