GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Engine 🢒 Engine Electrical 🢒 Engine Cranks But Does Not Run

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

Circuit/System Description

The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic table directs the service technician to the appropriate system diagnosis.

The Engine Cranks But Does Not Run diagnostic table assumes the following:

    • The batteries are completely charged. Refer to Battery Inspection/Test .
    • The cranking speed is within specifications. Refer to Engine Cranks Slowly .
    • There is adequate fuel in the fuel tanks.

Diagnostic Aids

If the cause of an engine cranks but will not run condition has not been found, inspect for the following conditions:

    • Hard starting only in cold ambient temperatures. These may cause an intermittent condition that may not occur in the service bay:
       - Fuel heater inoperative--Refer to Fuel Heater Inoperative .
       - Ice blockage at the fuel pickup in the fuel tank--This will be a high vacuum in the supply lines while cranking, and the problem will disappear after the vehicle is brought in the service bay. It may also exhibit a start and stall condition or a starting condition with no acceleration.
    • The correct cranking speed is 100 RPM cold and 180 RPM hot.
    • A basic engine problem
    • Low engine coolant may cause the engine to shut down.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Special Tools Required

J 44638 Vacuum Gage

Circuit/System Verification
  1. If DTCs P0090, P0191, P0193, P0335, P0336, P0340, P0602, P0603, P0604, P0606, P0642, P0643, P064C, P0698, P0699, P2510 are set diagnose those DTCs first.
  2. The engine starts and runs.
    3. ⇒If the engine does not start and run perform the Circuit/System Testing.

Circuit/System Testing
  1. Inspect for the following conditions:
    2. • Fuel smell or leak--Refer to Fuel Leak Diagnosis .
    • A plugged air filter collapsed air intake duct--Refer to Air Cleaner Element Replacement .
    • A restricted exhaust system--Refer to Symptoms - Engine Exhaust .
    • Contaminants in fuel--Refer to Contaminants-in-Fuel Diagnosis .
  2. Install the J 44638 to the fuel rail service port and crank the engine.
    3. ⇒If more than 5 inches Hg of vacuum was present during cranking, replace the fuel filter and inspect the fuel system restrictions.
  3. Perform the Engine Compression Test. Refer to Engine Compression Test .

    4. Important: During the replacement of the injectors, inspect the inlet and outlet fittings for corrosion or contamination. Refer to Contaminants-in-Fuel Diagnosis .

    ⇒If any fuel vapor was emitted during the engine compression test, replace the affected fuel injector. Refer to Fuel Injector Replacement .
  4. Assemble all disconnected components. Prime the fuel system to at least 10 psi. Attempt to start the engine.
    5. ⇒If the engine does start, refer to Fuel System Diagnosis .
    ⇒If the engine does not start, refer to Fuel System Diagnosis - High Pressure Side .

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Injector Replacement

Repair Verification

The engine starts and runs.