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Hombre (4.3L)

NOTE: For diagnosing fuel system, fuel pressure gauge SST J34730-1A or equivalent, TECH II scan tool or equivalent, SST J 42964-1 and J 42964-2 fuel line shut-off adaptors are required.
  1. Perform On-Board Diagnostic II (OBD-II) System Check. See ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK in SELF-DIAGNOSTICS - INTRODUCTION article. After performing OBD-II system check, go to next step.
  2. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  under FUEL SYSTEM. Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure test port. Turn ignition on with engine off. Use scan tool to command fuel pump ON. Insert pressure gauge bleed hose into an approved container and bleed the air out of the gauge. Close bleed valve and command fuel pump on again. Repeat several times until highest fuel pressure is obtained. Fuel pressure will drop slightly when pump stop running and should stabilize between 60-66 psi (4.2-4.6 kg/cm2 ). If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to step  11.
  3. Observe fuel pressure for ten minutes. If pressure drops more than 5 psi (.35 kg/cm2 ), go to step  8. If pressure does not drop more than specified, go to next step.
  4. Open fuel pressure gauge bleed valve and lower fuel pressure down to 10 psi (.7 kg/cm2 ). Observe fuel pressure for another ten minutes. It should not drop more than 2 psi (.14 kg/cm2 ). If fuel pressure drops more than specified, go to step  20. If fuel pressure does not drop more than specified, go to next step.
  5. If fuel pressure is suspected of dropping off during acceleration, cruise or hard cornering, go to step  7. If fuel pressure is not suspected of dropping during described conditions, go to next step.
  6. Start engine and allow to idle at normal operating temperature. Observe fuel pressure while quickly opening throttle. Pressure should approach 60-66 psi (4.2-4.6 kg/cm 2 ). If fuel pressure is as specified, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES article. If fuel pressure is not as specified, go to next step.
  7. Inspect for restricted fuel filter and fuel lines. Also inspect for high resistance in fuel pump wiring. See ENGINE PERFORMANCE WIRING DIAGRAMS article. Repair as necessary. If no problem was found, go to step  16.
  8. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Raise vehicle and disconnect fuel feed pipe from fuel filter outlet. Install SST J 42964-1 fuel pipe shut-off adaptor in line between fuel filter and fuel feed pipe. See Fig 1. Open valve on fuel pipe shut-off adaptor. Install fuel pressure gauge on fuel pipe shut-off adaptor test connection farthest away from fuel tank. Turn ignition on. Use scan tool to command fuel pump ON. Open bleed valve on fuel pressure gauge to purge air. Use scan tool again to command fuel pump ON. Wait for pressure to build up, then close valve on fuel pipe shut-off adaptor. Observe fuel gauge readings. If readings remain constant, go to step  20. If readings do not remain constant, go to next step.
    Fig 1: Identifying Fuel Return Pipe Shut-off Valve Adaptors
    G00009615Courtesy of ISUZU MOTOR CO.
  9. Inspect for fuel leaks at fuel pipe shut-off adaptor and fuel feed pipe. Repair as necessary. If no problem was found, go to next step.
  10. Open valve in fuel pipe shut-off adaptor. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Disconnect fuel return line quick connect fitting located near fuel filter. Install SST J 42964-2 fuel pipe shut-off adaptor into fuel return line. See Fig 1. Use scan tool to command fuel pump ON. Wait for pressure to build up, then close valve on fuel pipe shut-off adaptor in fuel return line. Observe fuel gauge readings. If readings remain constant, go to step  21. If readings do not remain constant, go to step  22.
  11. If fuel pressure is above 66 psi (4.6 kg/cm 2 ), go to next step. If fuel pressure is not higher than specified, go to step  14.
  12. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Raise vehicle and disconnect fuel feed pipe from fuel filter outlet. Also disconnect fuel return line quick connect fitting located near fuel filter. Drain any remaining fuel from the pipes into an approved container. Install SST J 42964-1 fuel pipe shut-off adaptor in line between fuel filter and fuel feed pipe. See Fig 1. Open valve on fuel pipe shut-off adaptor. Install fuel pressure gauge on either fuel pipe shut-off adaptor test connection. Install a flexible hose to fuel return line, and insert other end into approved container. Turn ignition on. Use scan tool to command fuel pump ON. Observe fuel gauge readings. If readings are between 60-66 psi (4.2-4.6 kg/cm2 ), go to step  23. If readings are not as specified, go to next step.
  13. Inspect fuel return lines for restrictions. Repair as necessary. If no problems were found, go to step  21.
  14. If fuel pressure is present, go to next step. If no fuel pressure is present, go to step  17.
  15. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Raise vehicle and disconnect fuel feed pipe from fuel filter outlet. Also disconnect fuel return line quick connect fitting located near fuel filter. Drain any remaining fuel from the pipes into an approved container. Install SST J 42964-1 fuel pipe shut-off adaptor in line between fuel filter and fuel feed pipe. Install SST J 42964-2 fuel pipe shut-off adaptor into fuel return line. Open valves on both adaptors. Install fuel pressure gauge on SST J 42964-1 fuel pipe shut-off adaptor test connection farthest away from fuel tank. Turn ignition on. Use scan tool to command fuel pump ON. Open bleed valve on fuel pressure gauge to purge air. Use scan tool again to command fuel pump ON. Slowly close valve on SST J 42964-2 fuel pipe shut-off adaptor installed in fuel return line. Observe fuel pressure. If readings rise above 66 psi (4.6 kg/cm 2 ), go to step  21. If readings do not rise above specified value, go to next step.
    CAUTION: DO NOT allow fuel pressure to rise above 75 psi (5.3 kg/cm2 ), otherwise fuel pressure regulator may be damaged.
  16. Inspect for poor electrical fuel pump connections or ground. Remove fuel pump and check for restricted fuel pump strainer or leaking fuel pump flex pipe. Also confirm that fuel pump is correct part for vehicle. Repair as necessary. If no problems were found, go to step  20.
  17. Turn ignition on. Use scan tool to command fuel pump ON. Listen for fuel pump operation. If fuel pump can be heard, go to next step. If fuel pump can not be heard, go to appropriate FUEL SYSTEM ELECTRICAL TEST .
  18. Visually inspect for the following: empty fuel tank, restricted fuel filter, fuel feed pipe or fuel pump strainer, or leaking fuel pump flex pipe. Repair any problems found as necessary. If no problems were found, go to next step.
  19. Inspect for leaking fuel feed pipe between fuel pipe shut-off adaptor and fuel pump/sending unit. Repair as necessary. If no leaks were found, go to next step.
  20. Replace fuel pump assembly. Test drive vehicle to confirm repairs.
  21. Replace fuel pressure regulator. Test drive vehicle to confirm repairs.
  22. Locate and replace any grounded fuel injectors. See FUEL INJECTION under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. If no injectors are grounded, check suspected leaking injector's spark plug for wetness. If unable to determine from viewing spark plugs, remove fuel metering body. Reinstall fuel hoses. Lift fuel metering body just enough to leave injector poppet nozzles in their ports. Use scan tool to pressurize fuel system and observe fuel injector poppet nozzles for leaks. Replace any leaking nozzles.
  23. Locate and repair restriction in fuel return pipe. Test drive vehicle to confirm repair.
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