Leak detection assembly

In a leak detection assembly for an evaporative emission control system in an automotive vehicle including a fuel tank, a canister for collecting volatile fuel vapors from the fuel tank, a purge valve disposed between the canister and an intake manifold of an engine operative to allow flow of the fuel vapors from the canister to the intake manifold, a vacuum actuated pump in communication with the canister having a first three-port solenoid fluidly connected to the intake manifold, and a vent control valve operative to selectively allow and prevent communication between the canister and a first atmospheric vent of the vacuum actuated pump, said leak detection assembly comprising:

• a second three-port solenoid fluidly connected to the vacuum actuated pump and the intake manifold and a second atmospheric vent;
• a vacuum line fluidly connecting said second three-port solenoid to the vent control valve, said second three-port solenoid selectively communicating with the intake manifold to allow a vacuum in said vacuum line during a first operating mode to close the vent control valve and selectively communicating with said second atmospheric vent during a second operating mode to open the vent control valve;
• a check valve disposed on said vacuum line connecting said second three-port solenoid with the intake manifold;
• and
• an engine control unit electrically connected to said first three-port solenoid of the vacuum actuated pump and the purge valve and said second three-port solenoid for closing the purge valve and for energizing said second three-port solenoid to cause a vacuum to be drawn in and close the vent control valve and seal the canister and for energizing said first three-port solenoid of the vacuum actuated pump to pressurize the evaporative emission control system and for de-energizing said first three-port solenoid of the vacuum actuated pump and said second three-port solenoid to cause atmospheric pressure from said second atmospheric vent to be drawn in and open the vent control valve to de-pressurize the evaporative emission control system.