System and method for controlling a vacuum pump that is used to check for leaks in an evaporative emissions system

A control system comprising:

• a fuel system diagnostic module that performs a diagnostic test on a fuel system when a vacuum pump is switched off to prevent flow through the vacuum pump and thereby seal a portion of the fuel system from an atmosphere, wherein the vacuum pump includes a cam ring, a rotor that rotates within the cam ring, and vanes that slide into and out of slots in the rotor as the rotor rotates;
• and
• a pump control module that switches on the vacuum pump for a predetermined period to force the vanes out of the slots and into contact with the cam ring to seal the vacuum pump before switching off the vacuum pump for the fuel system diagnostic test, wherein the fuel system includes a fuel tank, an evaporative emissions (EVAP) system that provides fuel vapor from the fuel tank to an engine, and an EVAP leak check (ELC) system that checks for leaks in the EVAP system, wherein the ELC system includes the vacuum pump and an ELC pressure sensor that measures pressure within the ELC system, wherein the EVAP system includes a canister that stores fuel vapor from the fuel tank and a purge valve that opens to allow fuel vapor to flow from the canister to an intake manifold of the engine, and wherein the fuel system diagnostic module selectively diagnoses a fault in the purge valve based on a change in the ELC system pressure when the vacuum pump is switched off.

A method comprising:

• performing a diagnostic test on a fuel system when a vacuum pump is switched off to prevent flow through the vacuum pump and thereby seal a portion of the fuel system from an atmosphere, wherein the vacuum pump includes a cam ring, a rotor that rotates within the cam ring, and vanes that slide into and out of slots in the rotor as the rotor rotates;
• and
• switching on the vacuum pump for a predetermined period to force the vanes out of the slots and into contact with the cam ring to seal the vacuum pump before switching off the vacuum pump for the fuel system diagnostic test, wherein the fuel system includes a fuel tank, an evaporative emissions (EVAP) system that provides fuel vapor from the fuel tank to an engine, and an EVAP leak check (ELC) system that checks for leaks in the EVAP system, wherein the ELC system includes the vacuum pump and an ELC pressure sensor that measures pressure within the ELC system, and wherein the EVAP system includes a canister that stores fuel vapor from the fuel tank and a purge valve that opens to allow fuel vapor to flow from the canister to an intake manifold of the engine, the method further comprising selectively diagnosing a fault in the purge valve based on a change in the ELC system pressure when the vacuum pump is switched off.