Mitsubishi Pick-ups and Montero 1983-1995 Repair Guide

Relieving Fuel System Pressure


The Multi-port Fuel Injection (MFI) system incorporate an electric fuel pump to create high pressures in the fuel lines. This pressure is needed to adequately feed the fuel through the injectors, which sufficiently vaporize the fuel in the runners of the intake manifold. Since the fuel pump creates such high pressures, the MFI system incorporates special fuel hoses designed to withstand these pressures.

Because of the systems high operating pressures, whenever the system is opened to the outside (loosening fuel lines or similar fuel components) the high pressure must first be relieved. The following procedure will lessen the fuel system pressure so that work can be accomplished:

  1. Remove the cover plate from over the fuel pump. The fuel pump cover plate is located under the rear carpeting in the trunk area of the truck or Montero.
  3. Label and unplug the harness connectors to the electric fuel pump.
  5. Start the vehicle and allow it to idle until it stalls on its own.
  7. Turn the ignition switch to OFF .
  9. Remove the negative (-) battery cable form the negative (-) terminal of the battery.
  11. The fuel system pressure should now be lowered to normal, however, when loosening fuel lines or related components have rags close at hand to soak up any residual gasoline in the system.