Grease gun including an air vent with a membrane for priming

A grease gun comprising:

• a housing;
• a motor supported in the housing;
• a pump assembly coupled to and driven by the motor;
• a pump housing supported in the housing and at least partially supporting the pump assembly, the pump housing at least partially defining a flow path;
• an air vent supported in the pump housing in fluid communication with the pump assembly and the flow path, the air vent configured to allow air to pass through the air vent to an exterior of the pump housing while retaining other fluids within the pump housing;
• and
• a membrane at least partially supported in the air vent that permits air to pass to the exterior of the pump housing.