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Home >> Lexus >> 1992 >> SC 300 Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Fuel System >> Fuel Pressure
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Fuel Pressure

  1. Check fuel pressure. Ensure a sufficient amount of fuel is in fuel tank. Turn ignition off. Locate check connector in engine compartment. Using a jumper wire, connect check connector terminals +B and FP. See Fig 1. Turn ignition on.
    Fig 1: Identifying Check Connector Terminals
    G92F26125Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. Using finger pressure, ensure fuel is felt in hose from fuel filter. When fuel system is pressurized, fuel return noise will also be heard. Turn ignition off.
  3. If no fuel pressure was felt, check fusible links, fuses, 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. On ES300, connect fuel pressure gauge to cold start injector fuel line. On LS400 and SC400, remove fuel filter and connect fuel pressure gauge to left fuel delivery pipe. On SC300, slowly loosen and remove union bolt holding delivery pipe to No. 1 fuel pipe. Connect fuel pressure gauge and No. 1 fuel pipe to delivery pipe. On all models, use a jumper wire and connect terminals FP and +B of check connector. See Fig 1. 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. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
    FUEL PRESSURE SPECIFICATIONS

    Application At Idle W/Vacuum psi (kg/cm2 ) At Idle W/O Vacuum psi (kg/cm2 )
    ES300 33-37 (2.3-2.6) 38-44 (2.7-3.1)
    LS400, SC300 & SC400 28-34 (2.0-2.4) 38-44 (2.7-3.1)
  6. Start engine. Disconnect and plug vacuum hose from fuel pressure regulator. Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS table. Unplug and reconnect 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 to less than specified value for 5 minutes after engine is turned off. See FUEL PRESSURE SPECIFICATIONS table.
  9. If fuel pressure is not as specified, check fuel pump, fuel pressure regulator and fuel injectors. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Remove fuel pressure gauge.
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