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CPI (4.3L)

  1. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Connect Fuel Pressure Gauge (J-34730-1) to fuel pressure connector on fuel rail. Turn ignition on. With ignition on and engine off, pressure should be 54-64 psi (3.8-4.5 kg/cm2 ) and should hold steady. If pressure is within specification and holds, go to next step. If pressure does not hold, go to step 3). If no fuel pressure is present, go to step 6). If pressure is greater than specification, go to step 8).
  2. Start engine. With engine at operating temperature, open throttle quickly and note fuel pressure. If pressure does not approach 64 psi (4.5 kg/cm2 ), replace CPI assembly. If pressure does approach 64 psi (4.5 kg/cm2 ), no problem is present.
  3. If pressure is within specification but does not hold, check for leaking injectors or fittings by pinching off fuel return line. If pressure does not hold, replace CPI assembly. If pressure does hold, check for faulty in-tank fuel pump or pump connections.
  4. If pressure is present but less than specification, check for restricted delivery line or fuel filter. Repair as necessary. If no restriction is evident, apply battery voltage to fuel pump test connector using a 10-amp fused jumper wire. For location of fuel pump test connector, see COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS article in this section.
  5. Gradually pinch off flexible fuel return line between CPI assembly and fuel tank. If fuel pressure increases to within specifications, pressure regulator is faulty. Replace CPI assembly. If fuel pressure does not increase with line pinched, check for faulty in-tank fuel pump, loose pump connections or partial blocked fuel strainer.
  6. Use a 10-amp fused jumper wire to apply battery voltage to fuel pump test connector. For location of fuel pump test connector, see COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS article in this section. 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.
  7. If fuel pressure is present with voltage applied to test connector, test fuel pump relay and voltage supply to relay. See SYSTEM/COMPONENT TESTS article in this section.
  8. Relieve fuel pressure. Disconnect flexible fuel return line. Attach 5/16 ID flexible fuel line to CPI side of fuel line. Route hose into appropriate container. Turn ignition on and note fuel pressure. If fuel pressure is within specification, locate and repair restriction in fuel return line.
  9. If fuel pressure is still greater than specification, replace CPI assembly.
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