Engine Cranks But Does Not Run
Engine Cranks But Does Not Run
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
Circuit/System Description
This Engine Cranks but Does Not Run diagnostic is an organized approach to identify a condition which causes the engine to crank but does not continue to run. This diagnostic directs the service technician to the appropriate system diagnosis. This diagnostic assumes the vehicle system voltage levels are adequate for starter motor operation. Refer to Battery Inspection/Test (Battery Inspection/Test) and Engine Cranks Slowly (Engine Cranks Slowly). The fuel level supply must be adequate, and the fuel quality must be able to sustain the combustion process.
Diagnostic Aids
Inspect for any of the following conditions:
* Insufficient fuel can cause a no start condition. Thoroughly inspect the fuel delivery system for sufficient fuel volume to the fuel injectors. Inspect the fuel supply components for partial blockage or restrictions.
* Fuel injectors with partially blocked and restricted nozzles, or a malfunctioning solenoid, can cause a no start condition.
* There may be fuel spray at the fuel injectors and the indicated fuel pressure may be correct, yet there may not be enough fuel to start the engine. If the fuel injectors and the injector circuit are OK and fuel spray is detected, the fuel injector ON time may be inadequate. If the engine control module (ECM) receives incorrect inputs from the various information sensors, the fuel delivered by the fuel injectors may be inadequate to start the engine. Observe all the engine data parameters with a scan tool and compare the values indicated with the expected values or the values from a known good vehicle.
* Observe the Engine Speed parameter while cranking the engine. The scan tool should indicate a steady 200-300 RPM while cranking. If erratic values such as sudden spikes in the engine speed are displayed, the engine reference signal is not stable enough for the engine to start and run properly.
* Inspect the engine for good secure electrical grounds.
* If the engine almost starts and then stalls, inspect for an open in the ground circuits of the CKP sensor and the camshaft position (CMP) sensor.
* Water or foreign material in the fuel can cause a no start or engine will not stay running condition. During freezing weather water can freeze inside the fuel system. The engine may start after 30 minutes in a heated repair shop. The malfunction may not recur until parked overnight in freezing temperatures. Extreme weather conditions can cause contaminated fuel to prevent the vehicle from starting.
* A vehicle that starts and runs after being brought to the repair shop for a no start condition may have an ignition system that is susceptible to moisture. Spray water on the ignition system components and the wiring in order to verify for an engine starting or will not stay running concern.
* When disconnecting electrical connectors or removing fuses and relays, always inspect electrical terminals for corrosion and for adequate terminal tension.
* Use the J 35616 for any test that requires probing the underhood electrical center terminals, component wire harness terminals, or the controller wire harness terminals.
Reference Information
Schematic Reference
Engine Controls Schematics (except L96) ([1][2]Electrical Diagrams)Engine Controls Schematics (L96) ([1][2]Electrical Diagrams)
Connector End View Reference
* Component Connector End Views (Connector End Views By Name)
* Electrical Center Identification Views (Application and ID)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Control Module References) for scan tool information
Special Tools
* CH-48027 Digital Pressure Gauge
* J 35616 GM-Approved Terminal Test Kit
* J 35616-A/BT-8637 Connector Test Adapter Kit
* J 43244 Relay Puller Pliers
Circuit/System Verification
1. Engine cranking for 15 seconds, observe the DTC information with a scan tool. Verify that DTC P0117, P0118, P0122, P0123, P0201-P0208, P0222, P0223, P0300-P0308, P0335, P0336, P0351-P0358, P0562, P0563, P0601-P0604, P0606, P0607, P062F, P0633, P0685, P0690, P1631, P1682, or P2610 is not set.
• If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).
2. Ignition ON, view the security indicator. The security indicator should not remain illuminated after the vehicle bulb check has completed.
• If the security indicator remains illuminated after the bulb check, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) , and diagnose any theft deterrent DTCs set as current.
3. Engine cranking, observe the scan tool Engine Speed parameter. The scan tool should indicate an engine speed greater than 0 RPM.
• If the engine speed is 0 RPM, refer to DTC P0335 (P0335) or DTC P0336 (P0336) for further diagnosis.
4. Verify the following scan tool parameters indicate OK when the engine is cranked:
* Cylinder 1-8 Injector Circuit Short to Ground Test Status
* Cylinder 1-8 Injector Circuit Open Test Status
• If the parameters do not indicate the specified values, refer to DTC P0201, P0202, P0203, P0204, P0205, P0206, P0207, or P0208 (P0201).
5. Verify the Cylinder 1-8 Injector Circuit Short to Volts Test Status scan tool parameter changes from NOT RUN to OK when the engine is cranked.
• If the parameter does not indicate the specified values, refer to DTC P0201, P0202, P0203, P0204, P0205, P0206, P0207, or P0208 (P0201).
Note: Additional DTCs may set when using the fuel pump output control.
6. Ignition ON, command the fuel pump ON with a scan tool. You should hear the fuel pump turn ON.
• If the fuel pump does not turn ON, refer to Fuel System Diagnosis (Without FPCM) (Testing and Inspection)Fuel System Diagnosis (FPCM) (Component Tests and General Diagnostics).
7. Ignition OFF, install the CH-48027 . Refer to Fuel Pressure Gauge Installation and Removal (Fuel Pressure Gauge Installation and Removal).
Note:
* The fuel pump may need to be commanded ON several times in order to obtain the highest possible fuel pressure.
* Do NOT start the engine for this test.
8. Ignition ON, command the fuel pump ON with a scan tool. The fuel pressure should be between 345-414 kPa (50-60 psi).
• If not within the specified range, refer to Fuel System Diagnosis (Without FPCM) (Testing and Inspection)Fuel System Diagnosis (FPCM) (Component Tests and General Diagnostics).
9. Verify the following conditions do not exist:
* Collapsed air intake duct to the throttle body
* Restricted air filter element
* Spark plugs for being fouled
* A skewed manifold absolute pressure (MAP) sensor-Refer to DTC P0106 (P0106).
* A skewed engine coolant temperature (ECT) sensor-Refer to DTC P0116 (Without L96) (P0116).
* Exhaust system restricted-Refer to Restricted Exhaust (Restricted Exhaust).
* Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) (Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool))Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool) (Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool)).
* Engine mechanical condition-Refer to Symptoms - Engine Mechanical (Symptoms - Engine Mechanical) or Engine Compression Test (Testing and Inspection).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.