Fuel pressure checks

NOTE: These are my notes from a generic fuel injection book.  Readings are approximate.  I have not done these procedures, but they sound reasonable to me.  Corrections and updates would be appreciated.

You will be working with gasoline, the most dangerous common substance on the planet.  Vapors can ignite from a spark or ember several feet away from the source of gasoline and it doesn't just burn, it bursts into flame explosively.  Don't screw around.  Be safe.  THINK.  It's best to have an extra set of hands and an extra brain around - preferably an aware one.  A fire extinguisher is an excellent idea, too.  Vaguely related side trip.

• Obtain the following:
  • 5/16" barbed brass joiner fitting
  • 5/16" barbed brass tee
  • three 5/8" hose clamps
  • 0 - 100 psi gauge
  • high-pressure hose sufficient to connect gauge to tee

   

• Relieve the fuel pressure
  • loosen the gas cap
  • remove the fuel pump fuse
  • crank engine until no firing
  • re-install the fuel pump fuse

   

• Install the tee and gauge
  • Cut the inlet line
    • it runs the width of the fuel rail and connects to the top right side of the rail as viewed from the front of the car
  • Install the tee in the line
  • Install the gauge to the tee
    • clamp all connections

     

• Disconnect the vacuum line from the fuel pressure regulator (top left of fuel rail, as viewed from the front) and plug the line
• Start the engine and read the pressure at idle
  • fuel pressure should read approximately 35 psi
• Reconnect the vacuum line to the pressure regulator
  • pressure should drop to approximately 30 psi
    • if no difference, the pressure regulator is bad
• if significantly less than stated pressures -
  • SLOWLY pinch the fuel return line (left side of rail as viewed from front, exiting from the bottom of he rail) and see if the pressure rises to at least 35 psi (do not exceed 80 psi)
    • if so, the pressure regulator is bad
    • if not, the pump is probably bad fuel delivery
• If significantly greater than stated pressures -
  • cut the engine off, bleed fuel pressure off as before, remove the return line from the bottom of the fuel rail and connect a length of  line from the rail outlet to an external container (1 gallon minimum, to collect the gasoline)
  • Restart the engine and check the pressure (stop engine quickly to avoid pumping more as than the container can hold)
    • pressure correct?
      • fuel return line is blocked
    • pressure still high?
      • pressure regulator is bad

When finished, disconnect the tee & gauge assembly and reconnect the fuel supply line using the barbed connector and two clamps.  Make sure the fuel return line is securely installed.