Ford Mustang/Capri 1979-1988 Repair Guide

Relieving Fuel System Pressure


On vehicles with fuel injected engines, fuel lines remain pressurized even after the ignition is switched off. Therefore, it is critical to relieve pressure from the fuel system before disconnecting any fuel line or component.

As a safety feature, electronic fuel injected engines are equipped with a pressure relief valve. On the 4-140 engine with EFI, this valve is located in the flexible fuel supply tube approximately 12 in. (305mm) back from where it connects to the engine fuel rail, on the driver's side of the engine compartment.On the 8-302 engine with SEFI, the valve is located in the metal fuel line at the left front corner of the engine.Before opening the fuel system on EFI or SEFI engines, relieve fuel pressure as follows:

  1. Remove the fuel tank cap.
  3. Disconnect the vacuum hose from the fuel pressure regulator located on the engine fuel rail.
  5. Using a hand vacuum pump, apply about 25 in. Hg pressure to the pressure regulator. Fuel pressure will be released into the fuel tank through the fuel return hose.