Cars Technical Articles - GM Vehicles Diagnostic Tip for Crank or No Start

GM Vehicles Diagnostic Tip for Crank or No Start

- Edited: Aug 21, 2022
- Popularity: 96 Views

Makes:

GMC

Vehicles Affected:

  • 2016-2019 Cadillac CTS
  • 2015-2020 Cadillac Escalade
  • 2016-2019 Chevrolet 3500/4500 Medium Duty (LCF)
  • 2016-2020 Chevrolet Camaro
  • 2014-2019 Chevrolet Corvette
  • 2011-2020 Chevrolet Express
  • 2019-2020 Chevrolet Silverado
  • 2015-2020 Chevrolet Suburban
  • 2015-2020 Chevrolet Tahoe
  • 2011-2020 GMC Savana
  • 2010-2020 GMC Sierra
  • 2015-2020 GMC Yukon

Condition:

There is a concern that the vehicle cranks but doesn't start.

Cause:

This condition may be caused by a sheared camshaft sprocket locating pin.

  • The camshaft may seize to the camshaft bearings at one time during engine operation.
  • On rare occasions, a crank no start may be encountered.

  • Correction:

    During diagnosis, the technician will find proper fuel pressure, spark from each spark plug wire, and proper injector pulse. However, the following concerns will be noted during their diagnosis:

  • Low static compression
  • Excessive cylinder leakage past an intake or exhaust valve
  • The engine may start, but runs poorly if the CMP sensor is disconnected
  • The valve train may not move while cranking the engine

    If this concern is encountered, refer to the Service Procedure below and perform the suggested steps as necessary.

  • Service Procedure:

    Service Procedure
    1. Crank the engine while checking for movement in the valve train.
    Note: This can be done by shining light down the oil fill tube on most models.
    • If the valve train appears to be moving normally while the crankshaft is turning, continue to step 2.
    • If you determine valve train is not moving while the crankshaft is turning, move ahead to step 4.

    2. Disconnect the CMP sensor to see if the engine will start. If the engine starts, move ahead to step 4.
    3. Perform the following SI diagnostic procedures as necessary:
    3.1. Engine Cranks But Does Not Run diagnosis.
    3.2. Engine Compression Test (document results).
    3.3. Cylinder Leakage Test (document results).
    ⇒ If the SI procedures above isolate an engine mechanical concern (low compression; excessive cylinder leakage through the exhaust or intake, any type of valve train damage, etc.), continue to step 4.
    Note: Before removing the front cover, verify the ECM calibrations in case engine replacement is necessary.
    4. After completing steps 1, 2, or 3, remove the front cover to inspect for a sheared cam sprocket locator pin.
    ⇒ If the cam sprocket locator pin has sheared, engine replacement is required