System and method for diagnosing faults in vacuum pumps of fuel systems and for diagnosing leaks in fuel systems

A method, comprising:

• actuating a switching valve in a fuel system of a vehicle between a first position and a second position, the first position venting a suction side of a vacuum pump in the fuel system to an atmosphere, the second position sealing the suction side of the vacuum pump from the atmosphere;
• determining a first pressure on the suction side of the vacuum pump when the switching valve is in the first position;
• determining a second pressure on the suction side of the vacuum pump when the switching valve is in the second position;
• and
• selectively determining that the vacuum pump is stuck on based on the first pressure and the second pressure.

A method, comprising:

• actuating a switching valve in a fuel system of a vehicle between a first position and a second position, the first position venting a suction side of a vacuum pump in the fuel system to an atmosphere, the second position sealing the suction side of the vacuum pump from the atmosphere;
• determining a first pressure on the suction side of the vacuum pump when the switching valve is in the first position;
• determining a second pressure on the suction side of the vacuum pump when the switching valve is in the second position;
• selectively diagnosing a fault in the vacuum pump based on the first pressure and the second pressure;
• and
• determining that the vacuum pump is stuck on when a first difference between the first pressure and the second pressure is greater than a first threshold.