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HOMESERVICE MANUALSSATURN1991SC AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - BASIC TESTINGBASIC FUEL SYSTEM CHECKS (A-7)FUEL SYSTEM PRESSURE TEST (SATURN)FUEL PRESSURE CHECK (TBI)
1991 Saturn SC Automatic

Fuel Pressure Check (TBI)

1991 Saturn SC AutomaticSECTION Fuel Pressure Check (TBI)
  1. Relieve fuel pressure as previously described in FUEL PRESSURE RELIEF (TBI & PFI). With fuel gauge installed at fuel rail connector, turn ignition on. With ignition on and engine off, pressure should read within specification. See FUEL PRESSURE table. If no fuel pressure is present, go to step 5). If fuel pressure is less than specification, go to step 3). If pressure is within specification, turn ignition off. Pressure should hold. If pressure holds, system is functioning properly. If pressure does not hold, go to step 7).
  2. If pressure is present but is greater than specification, check fuel return line for blockage by disconnecting return line and placing it into a container. Turn ignition on. If fuel pressure is still not within specification, replace fuel pressure regulator. If fuel pressure is within specification, repair blockage in fuel system return line.
  3. If pressure is present but less than specification, check for restricted delivery line or fuel filter. Repair as necessary. If no restriction is evident, turn ignition off. Bleed off fuel pressure. Install fuel return line plug, available with fuel pressure gauge kit. Apply battery voltage to fuel pump test connector using a 10-amp fused jumper wire. Fuel pump test connector is located in rear compartment on driver's side behind carpet. See Fig 1.
  4. If fuel pressure increases to within specification, replace fuel pressure regulator. If fuel pressure does not increase with line pinched, check for faulty in-tank fuel pump or partially blocked fuel strainer.
  5. Apply battery voltage to fuel pump test connector using a 10-amp fused jumper wire. Fuel pump test connector is located in rear compartment on driver's side behind carpet. See Fig 1. Observe fuel pressure reading. If fuel pressure is still not present, check wiring between test connector and fuel pump. If wiring is okay, replace fuel pump.
  6. If fuel pressure is present with voltage applied to test connector, test fuel pump relay and voltage supply to relay. Refer to appropriate I - SYS/COMP TESTS article in this section.
  7. If pressure does not hold with ignition off, bleed off fuel pressure. Install fuel return line plug, available with fuel pressure gauge kit. Turn ignition on. Cycle key on and off several times to obtain accurate pressure reading. Allow pressure to stabilize for 30 seconds. Monitor fuel pressure reading for 5 minutes. Repeat test at least 2 more times.
  8. Pressure drop in 5 minutes should not exceed 6-8 psi (.4-.6 kg/cm2 ). If pressure does not hold, fuel pump check valve is bad, or injectors or fittings are leaking. To test fuel pump check valve, turn ignition off. Bleed off fuel pressure. Connect fuel pressure gauge to fuel delivery line. Close valve on pressure gauge.
  9. Turn ignition on. Cycle key on and off several times to obtain accurate pressure reading. Allow pressure to stabilize for 30 seconds. Monitor fuel pressure for 5 minutes. Repeat test at least 2 more times. Pressure reading should be 58-94 psi (4.0-6.5 kg/cm2 ) and should not leak down more than 6-8 psi (.4-.6 kg/cm2 ). If no leakage is present, problem is leaking injectors or fittings. If pressure leakage is excessive, check for external leaks. If no leaks are present, check fuel pump and connections inside of fuel tank.
Fig 1: Fuel Pump Test Connector Component Location (Saturn)
G50H16722
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