Electric fuel pumps are a vital part of any electronic fuel injection system because achieving an accurate air/fuel mixture ratio depends upon the fuel injector receiving adequate fuel pressure and volume. Because electric fuel pumps have moving parts that wear out, they also have a relatively predictable service life and, therefore, become a predictable profit center for the independent import service specialist. In addition, a fuel pump replacement should include a new in-tank filter, in-line fuel filter and a new fuel pressure regulator if testing indicates the need for replacement.

Most current import vehicle applications incorporate an in-tank, single- or dual-line fuel pump configuration. The single-line configuration regulates the fuel pressure at the fuel pump and operates with no fuel return line. The dual-line configuration, on the other hand, regulates fuel pressure at the end of the fuel injector delivery rail and excess fuel is returned to the tank via a separate fuel line.

The pulse-modulated, single-line electric fuel pump is a more recent configuration that is designed to vary fuel pressure according to engine demand and driving conditions. In the pulse-modulated configuration, a fuel pressure sensor mounted on the fuel injector rail provides a pressure input to the engine's powertrain control module (PCM). When the PCM calculates the pressure needed to meet a specific driving condition, it signal...