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Home >> Lexus >> 1998 >> GS 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Fuel System >> Fuel Pressure
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Fuel Pressure

  1. Ensure battery is fully charged. Turn ignition off. Disconnect negative battery cable. On ES300, go to next step. On GS300 and SC300, go to step 3). On LS400 and SC400, go to step 4).
  2. On ES300, place container under fuel filter. Cover fuel filter outlet banjo bolt with shop towel. Slowly loosen banjo bolt to relieve fuel pressure. Remove banjo bolt and gaskets. Go to step 5).
  3. On GS300 and SC300, disconnect vacuum pipe from rear of air intake chamber (to access fuel hose). Cover fuel inlet hose banjo bolt (at fuel rail) with shop towel. Slowly loosen banjo bolt to relieve fuel pressure. Remove banjo bolt and gaskets. Go to step 5).
  4. On LS400 and SC400, remove fuel pressure pulsation damper, located at rear of right fuel rail. Cover fuel inlet hose banjo bolt (at fuel rail) with shop towel. Slowly loosen banjo bolt to relieve fuel pressure. Remove banjo bolt and gaskets. Go to next step.
  5. On ES300, install Fuel Pressure Gauge (SST 09268-45012). On all models except ES300, install Fuel Pressure Gauge (SST 09268-45014), gaskets and banjo bolt. On all models, tighten banjo bolt. Reconnect negative battery cable. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure.
  6. Using scan tool manufacturer's instructions, activate electric fuel pump and note fuel pressure. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm2 ). Remove scan tool from DLC No. 3. Start engine and allow to idle. Note fuel pressure. Fuel pressure should be 44-50 psi (3.1-3.5 kg/cm2 ).
  7. If fuel pressure exceeds specification, replace fuel pressure regulator. If fuel pressure is less than specified, check for defective fuel lines, connections, fuel pump, fuel filter, fuel pressure regulator or fuel pressure control Vacuum Switching Valve (VSV), if equipped.
  8. Shut engine off and note fuel pressure. Fuel pressure should hold at least 21 psi (1.5 kg/cm2 ) for a minimum of 5 minutes. If fuel pressure does not hold as specified, check for defective fuel pump, fuel injector or fuel pressure regulator. See SYSTEM/COMPONENT TESTS article.
  9. Disconnect negative battery cable. Remove fuel pressure gauge. Reinstall banjo bolt using NEW gaskets. Tighten banjo bolt. Install negative battery cable.
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