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Engine Cranks But Does Not Start: Wrangler

  1. The following checks must be performed before continuing with this test.
    • Ensure battery is fully charged and in good condition.
    • Ensure Powertrain Control Module (PCM) power and ground circuits are okay. See COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
    • Ensure PCM communicates with scan tool and no Diagnostic Trouble Codes (DTC) are present. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - WRANGLER article.
    • Ensure PCI bus is functional. Using scan tool, attempt to communicate with instrument cluster and Sentry Key Immobilizer Module (SKIM). If scan tool does not communicate with instrument cluster or SKIM, diagnose communication failure. See COMMUNICATIONS in BODY CONTROL MODULES - WRANGLER article in ACCESSORIES & EQUIPMENT.
    • Using scan tool, select CLEAR PCM (BATT DISCONNECT). Crank engine over several times. Using scan tool, check for DTCs. If any DTCs are present, perform appropriate diagnostic test. See SELF-DIAGNOSTICS - WRANGLER article. If no DTCs exist, go to next step.
  2. Turn ignition on. Using scan tool, monitor SECONDARY INDICATORS while cranking the engine. If no SECONDARY INDICATORS exist, go to next step. If any SECONDARY INDICATORS exist, perform appropriate symptom related test. See TROUBLE SHOOTING - NO CODES article.
  3. Turn ignition off. Check Power Distribution Center (PDC) and fuse block for blown fuses. PDC is located on right side of engine compartment, next to battery. Fuse block is located behind glove box. Replace blown fuses and check related circuits for short to ground. If fuses are okay, go to next step.
  4. Using scan tool in SENSOR mode, monitor CURRENT CKP COUNT while cranking engine. If CKP count changes while cranking engine, go to next step. If CKP count does not change while cranking engine, go to DTC P0320: NO CRANK REFERENCE SIGNAL AT PCM under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - WRANGLER article.
  5. Using scan tool in SENSOR mode, monitor CURRENT CMP COUNT while cranking engine. If CMP count changes while cranking engine, go to next step. If CMP count does not change while cranking engine, go to DTC P0340: NO CAM SIGNAL AT PCM under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - WRANGLER article.
  6. Using scan tool in INPUTS/OUTPUTS mode, read CURRENT SYNC STATE while cranking engine. If scan tool does not display OUT OF SYNC, go to next step. If scan tool displays OUT OF SYNC, check Crankshaft Position (CKP) sensor signal circuit for short to Camshaft Position (CMP) sensor signal circuit. See WIRING DIAGRAMS article. Repair wiring as necessary. If wiring is okay, check for incorrect valve timing. Repair valve timing as necessary. See appropriate article in ENGINES. Also check for a CMP sensor drive problem.
  7. Using scan tool, actuate Auto Shutdown (ASD) fuel system test. Using a mechanic's stethoscope, listen for fuel pump operation at fuel tank. If fuel pump operation cannot be heard, stop ASD fuel system actuation and go to step  14 . If fuel pump operation can be heard, stop ASD fuel system actuation and go to next step.
    8. WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL SYSTEM PRESSURE RELEASE  .
  8. Turn engine off. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  . Remove test port cap. Install a 0-60 psi (0-4.2 kg/cm2 ) fuel pressure gauge at test port. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test. Allow fuel pressure gauge to stabilize. Stop ASD fuel system activation. Fuel pressure should be 44.2-54.2 psi (3.23-3.96 kg/cm2 ). If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, replace fuel filter/pressure regulator. Fuel filter/fuel pressure regulator is located in top of fuel tank. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pressure is as specified, go to step  11 .
    9. WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL SYSTEM PRESSURE RELEASE  .
  9. Turn ignition off. Check for restricted fuel supply line between fuel rail and fuel pump module. Fuel pump module is located in fuel tank. Repair fuel line as necessary. If fuel line is okay, go to next step.
  10. 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 is not plugged, replace fuel pump.
  11. 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.
    12. CAUTION: DO NOT operate fuel pump longer than 7 seconds.
  12. Using scan tool, actuate ASD fuel system test for 7 seconds. If fuel volume is .5 pt. (.25L) or more, fuel volume is okay. Stop fuel system activation. Remove all test equipment and reconnect fuel supply line to fuel rail. Go to next step. 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.
  13. Check the following additional items as possible causes for no-start condition:
    • Check spark plug condition.
    • Fuel must be free of contamination.
    • Engine exhaust system must be free of restrictions.
    • Engine compression must be within specification.
    • Engine valve timing must be within specification.
    • Engine vacuum must be at least 13 in. Hg with shift selector in Neutral.

    Repair any problems as necessary. If no problems exist, test is complete.

  14. 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/White 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  17 .
  15. 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.
  16. At this time, fuel pump module is assumed to be defective. Replace fuel pump module.
  17. Turn ignition off. Ensure fuel pump module is disconnected. Remove fuel pump relay from PDC. Using a test light connected to ground, probe Dark Green/Black wire at terminal C10 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 Dark Green/Black wire between fuel pump relay socket and PDC. Also check fuse No. 23 (20-amp) in PDC.
  18. Measure resistance of Dark Green/White wire between fuel pump module harness connector and terminal C9 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/White wire between fuel pump module and PDC.
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