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Home >> Hummer >> 2007 >> H2 4D Utility Pickup >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 6.0L - Troubleshooting >> Hard Start

Hard Start

Hard Start

Inspection/Test Action
DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.
Preliminary
Sensor/System
  • Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Connect a scan tool. Compare the engine coolant temperature to the intake air temperature (IAT) on a cold engine. The ECT and IAT sensor values should be within ± 3°C (5°F) of each other. If the ECT sensor is out of range with the IAT sensor, measure the resistance of the ECT sensor. Refer to Temperature Versus Resistance for resistance specifications.
  • IMPORTANT: The embossed arrows on the MAF sensor indicate the direction of the intake air flow. The arrows must point toward the engine.
  • Inspect the mass air flow (MAF) sensor installation. A MAF sensor that is incorrectly installed may cause a hard start. Install the MAF in the proper direction. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .
  • Inspect the camshaft position (CMP) sensor for proper mounting and/or a bad connection. An extended crank occurs if the PCM does not receive a CMP signal.
Fuel System
Ignition System
  • Verify that both fuel injector fuses are not open. An open fuel injector fuse causes 4 ignition coils and 4 fuel injectors not to operate. Inspect the ignition coil circuits and the fuel injector circuits for an intermittent short to ground. Refer to Circuit Testing . Replace the fuse.
  • Inspect for proper ignition voltage output with the J 26792  Spark Tester. See Special Tools . Refer to Electronic Ignition (EI) System Diagnosis .
  • Remove the spark plugs and inspect for the following:
    • Correct heat range
    • Wet plugs
    • Cracks
    • Wear
    • Improper gap
    • Burned electrodes
    • Heavy deposits
Refer to Spark Plug Inspection .
Engine Mechanical Inspect for the following conditions: