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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 12 (Engine Controls - 6.6L - Troubleshooting & Diagnosis) >> Hard Start

Hard Start

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Hard Start

Inspection Action
DEFINITION: The engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but immediately dies.
Preliminary Inspection
Sensor Inspection
  • Inspect the engine coolant temperature (ECT) sensor. Use the scan tool to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, inspect for a high resistance in the coolant sensor circuit or the sensor itself.
  • Turn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure (FRP) should be between 1.1-1.8 MPa. If it is not, inspect for high resistance in the FRP sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs .
  • Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Fuel System Inspection
  • Inspect the fuel pressure regulator 12-volt circuit for an intermittent short to ground. Observe the FRP Command percent while cranking. A range of 85-95 percent indicates a possible short to ground condition.
  • Inspect the fuel supply to the fuel injection pump. Refer to Fuel System Diagnosis .
  • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
  • Inspect for air in the fuel system. Refer to Fuel System Diagnosis .
  • Inspect for external fuel leaks. Refer to Fuel Leaks .
  • Inspect for high engine oil level. Refer to Fuel in Engine Oil .
  • Inspect for low fuel pressure. Command the fuel pressure to 160 MPa with a scan tool while the engine is at idle. If 160 MPa is not achieved, perform Fuel System Diagnosis - High Pressure Side .
  • At idle observe the FRP Regulator Fuel Flow Command parameter with a scan tool. If the FRP Regulator Fuel Flow Command is more than 2700 mm3 , perform the Fuel System Diagnosis - High Pressure Side .
  • Inspect the fuel tank cap vent for proper operation.
Electrical System Inspection Inspect for a slow cranking speed. Refer to Symptoms - Engine Electrical .
Air Intake System Inspection
  • Inspect the air cleaner and air intake ducts for a restrictions or leaks.
  • Inspect for a restriction in turbocharger inlet duct.
  • Inspect for a restriction or a leak in the intake manifolds.
Exhaust System Inspection Inspect the exhaust system for a possible restriction. Refer to Restricted Exhaust .
Engine Mechanical Inspection Inspect the engine for the following conditions:
Additional Inspection