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Home >> Lexus >> 1990 >> ES 250 Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Fuel Pump & Fuel Pressure Regulator
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Fuel Pump & Fuel Pressure Regulator

  1. Turn ignition on. DO NOT  start engine. Using a jumper wire, connect terminals FP and +B of check connector. See Figure.
  2. Using fingers, ensure fuel pressure is felt in hose from fuel filter. When fuel system is pressurized, a fuel return noise will also be heard. Turn ignition off.
  3. If no fuel pressure was felt, check fusible links, fuses (EFI 15-amp and IGN 7.5-amp), EFI main relay, fuel pump, ECU and wiring connections.
    CAUTION: SLOWLY loosen cold start injector fuel line to avoid fuel spraying onto skin, eyes and vehicle finish.
  4. Connect a fuel pressure gauge to cold start injector fuel line. Using a jumper wire, connect terminals FP and +B of check connector. See Figure. Turn ignition on. Check fuel pressure.
  5. See FUEL PRESSURE SPECIFICATIONS  table. If fuel pressure is more than specification, replace fuel pressure regulator. If fuel pressure is less than specification, check fuel hoses, hose connections, fuel pump, fuel filter and fuel pressure regulator.
    FUEL PRESSURE SPECIFICATIONS

    Application psi (kg/cm2 )
    Ignition On, Engine Off 38-44 (2.7-3.1)
    Engine Idling(1) 38-44 (2.7-3.1)
    Engine Idling (2) 33-37 (2.3-2.6)
    Ignition Off, Engine Off 21 (1.5)
    (1) With fuel pressure regulator vacuum hose disconnected.
    (2) With fuel pressure regulator vacuum hose connected.
  6. Start engine. Disconnect and plug vacuum hose from fuel pressure regulator. Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS  table. Unplug and connect vacuum hose to fuel pressure regulator.
  7. Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS  table. If fuel pressure is not within specification, check fuel pressure regulator and vacuum hose.
  8. Turn engine off. Ensure fuel pressure does not drop less than specified value for 5 minutes after engine is turned off. See the FUEL PRESSURE SPECIFICATIONS  table. If fuel pressure is not as specified, check fuel pump, fuel pressure regulator and fuel injectors. Remove fuel pressure gauge.
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