LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mitsubishi >> 1999 >> Eclipse GS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Fuel System >> Fuel Pressure >> All Models Except Eclipse 2.0L Non-Turbo
April 5, 2026: LEMON Manuals is launched! Read the announcement.

All Models Except Eclipse 2.0L Non-Turbo

WARNING: Before disconnecting high pressure fuel hose at fuel delivery pipe, cover fuel hose connection with a rag. Some residual fuel pressure may still be in system.
  1. Relieve fuel pressure. See RELIEVING FUEL PRESSURE . Disconnect high pressure fuel inlet line at fuel rail. Remove throttle body bracket (if necessary). Connect fuel pressure gauge with adapter between fuel rail and high pressure fuel inlet line. See Fig 1. Use scan tool to operate fuel pump. Ensure no fuel leaks are present.
  2. Start engine and allow it to idle. Measure fuel pressure with vacuum hose connected to fuel pressure regulator. Record fuel pressure reading. See FUEL PUMP PERFORMANCE  table. Disconnect and plug vacuum hose from fuel pressure regulator. Record fuel pressure reading.
    FUEL PUMP PERFORMANCE

    Application At Idle w/Vacuum psi (kPa) At Idle w/o Vacuum psi (kPa)
    Eclipse 2.0L
    Non-Turbo (1) (1)
    Turbo 33 (228) 42-45 (290-310)
    3000GT Turbo 34 (234) 43-45 (296-310)
    All Other Models 38 (262) 47-50 (324-345)
    (1) With key on engine off, pressure should be 47-50 psi (324-345 kPa)
  3. Check for fuel pressure in fuel return hose by gently pinching hose while increasing engine speed. If fuel volume is low, fuel pressure in return hose will not be felt. Increase engine speed to 2500-3000 RPM, 2-3 times. Return engine to idle. Fuel pressure should not drop when engine is returned to idle.
  4. Turn ignition off. Ensure fuel pressure reading does not decrease within 2 minutes. If a decrease is noted, monitor speed of decrease.
  5. If fuel pressure is lower than specification, fuel pressure drops at idle after increasing engine speed to 2500-3000 RPM, or no fuel pressure in fuel return hose can be felt, check for clogged fuel filter, or faulty fuel pressure regulator or fuel pump.
  6. If fuel pressure is greater than specification, check for a faulty fuel pressure regulator or plugged fuel return line. If fuel pressure does not change when vacuum hose to regulator is connected or disconnected, check for a leaking or clogged vacuum hose to fuel pressure regulator or faulty fuel pressure regulator.
  7. If fuel pressure decreases suddenly after engine is stopped, check valve in fuel pump is not seated. Replace fuel pump. If fuel pressure drops slowly, fuel injector is leaking or fuel pressure regulator valve seat is leaking. Check for faulty fuel injector or fuel pressure regulator. Repair as necessary.
  8. When fuel pressure test is complete, repeat fuel pressure release procedure before disconnecting fuel pressure gauge. Install NEW "O" ring at end of high pressure fuel inlet line. Check for fuel leaks.
Fig 1: Installing Fuel Pressure Tester (Typical)
G95H31028Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.