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Checking Fuel Delivery (Grand Cherokee)

  1. Turn ignition on. Using scan tool, actuate ASD fuel system test. Listen for fuel pump operation at fuel tank. It may be necessary to use a stethoscope. If fuel pump operation can be heard, fuel pump is operating. Stop fuel system activation and go to next step. If fuel pump operation cannot be heard, stop fuel system activation and go to step  7 .
  2. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  . Remove test port cap on fuel rail. Install a 0-60 psi (0-4.2 kg/cm2 ) fuel pressure gauge at test port. Start engine and allow to idle. Fuel pressure should be 44.2-54.2 psi (3.1-3.7 kg/cm2 ). If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, check fuel return line for kinks or restrictions. See Fig 1 . Repair fuel return line as necessary. If fuel return line is okay, replace fuel filter/pressure regulator. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is as specified, go to step  5 .
    Fig 1: Locating Fuel Filter/Pressure Regulator (Grand Cherokee)
    G00010247Courtesy of DAIMLERCHRYSLER CORPORATION
  3. If engine runs but fuel pressure is less than specified, check for kinked or damaged fuel supply line between fuel pump module and fuel rail. Repair fuel line as necessary and retest. If fuel line is okay, release fuel pressure. Raise and support vehicle. Disconnect fuel pressure line from fuel filter/pressure regulator. See Fig 1 . Connect Fuel Line Pressure Test Adapter Hose (6539) between disconnected fuel line and fuel filter/pressure regulator. Connect fuel pressure gauge to fuel line adapter hose. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test and note fuel pressure. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm2 ). If fuel pressure is within specification, stop ASD fuel system activation, release fuel pressure and replace fuel filter/pressure regulator. If fuel pressure is not within specification, stop ASD fuel system activation and go to next step.
  4. Turn ignition off. Release fuel pressure. Remove fuel pump module and inspect fuel inlet strainer. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel inlet strainer is plugged, replace fuel pump inlet strainer. If fuel inlet strainer in not plugged, replace fuel pump.
  5. Turn ignition off. Release fuel pressure. Disconnect fuel supply line from fuel rail. Install Fuel Line Pressure Test Adapter Hose (6539 for 5/16" fuel lines or 6631 for 3/8" fuel lines) between disconnected fuel line and fuel rail. Remove fuel fill cap. Insert other end of hose into a graduated container suitable for gasoline.
    6. CAUTION: DO NOT operate fuel pump longer than 7 seconds.
  6. Using scan tool, actuate ASD fuel system test for 7 seconds. If fuel volume is .5 pt. (.25L) or more, no problem is indicated at this time. Test is complete. If fuel volume is less than .5 pt. (.25L), check for a kinked fuel line between fuel pump module and fuel rail. Repair fuel lines as necessary and retest. If fuel line is okay, replace fuel pump module assembly. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article.
  7. Turn ignition off. Disconnect fuel pump module connector. Turn ignition on. Using scan tool, actuate ASD fuel system test. Using a test light connected to ground, probe Dark Green/Black wire at fuel pump module harness connector. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, go to step  10 .
  8. Turn ignition off. Disconnect test light. Using a test light connected to positive battery voltage, probe Black wire at fuel pump module harness connector. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open in Black wire between ground and fuel pump module. See WIRING DIAGRAMS article.
  9. At this time, fuel pump module is assumed to be defective. Replace fuel pump module.
  10. Turn ignition off. Ensure fuel pump module is disconnected. Remove fuel pump relay from PDC. Using a test light connected to ground, probe terminal No. 30 (Violet/White wire) at fuel pump relay socket in PDC. See Figure . If test light illuminates, go to next step. If test light does not illuminate, repair open in Violet/White wire between fuel pump relay socket and PDC. Also check fuse No. 24 (20-amp) in PDC.
  11. Measure resistance of Dark Green/Black wire between fuel pump module harness connector and terminal No. 87 at fuel pump relay socket in PDC. See Figure . If resistance is less than 5 ohms, circuit is okay. Replace fuel pump relay. If resistance is 5 ohms or more, repair open in Dark Green/Black wire between fuel pump module and PDC.
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