Mechanical Fuel Pump
Fuel pumps are either mechanical or electrical. Mechanical, or diaphragm, pumps are found on older car models. These pumps are at the front side of the engine and are typically connected to the crankshaft by a lever. The rotary motion of the crankshaft moves the lever up and down, thus pumping the fuel.
MECHANICAL FUEL PUMP
One disadvantage to mechanical pumps is that some are susceptible to vapor lock. Heat from the engine block plus low pressure at the fuel intake side of the pump combine to promote fuel evaporation (liquids boil and evaporate easier at high temperature and low pressure). The vapor bubbles interrupt the flow of fuel to the engine and cause stalling or hard starting. If vapor lock occurs, cover the pump and fuel lines with a cold wet cloth to condense the fuel.
