Engine Cranks But Does Not Run
Engine Cranks But Does Not Run (LSA)
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 Testing and Inspection. The fuel level supply must be adequate, and the fuel quality must be able to sustain the combustion process.
Diagnostic Aids
* When attempting to start the engine, the mechanical portion of the vehicle key must be locked in the fully extended position with the fob parallel to the key. Leaving the key partially retracted or folded over when starting may interrupt transponder authentication and result in an intermittent no-start condition. In such instances, DTC B3055 may also be set. If an intermittent no-start complaint is received, it may be necessary to discuss with the customer their starting habits and verify they are locking the key in the fully extended position, fob parallel to the key, before starting.
* 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. Refer to Fuel Injector Diagnosis (CH47976) Fuel Injector Diagnosis (CH47976)Fuel Injector Diagnosis (J39021 or Scan Tool) Fuel Injector Diagnosis (J39021 or Scan Tool).
* 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. Check 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, check for an open in the ground circuits of the crankshaft position sensor and the camshaft position 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 check for an engine starting or will not stay running concern.
* Use the J 35616 - Test Kit for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness terminals.
Reference Information
Schematic Reference
Engine Controls Schematics (L99/LS3) [1][2]Electrical DiagramsEngine Controls Schematics (LSA) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly - Primary
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 - Fuel Pressure Gauge
* J 37287 - Fuel Line Shut-Off Adapters
* J 26792 - HEI Spark Tester
Circuit/System Verification
Note: This diagnostic assumes the following:
* The battery is completely charged.
* The engine cranking speed is acceptable.
* There is adequate fuel in the fuel tank.
Attempt to start the engine. The engine should start and continue to run. An engine that starts and stalls is considered to not run.
If the vehicle passes the Circuit/System Verification test, refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.
Circuit/System Testing
1. Crank the engine while observing the scan tool Vehicle DTC Information. Verify that DTC P0117, P0118, P0122, P0123, P0201-P0208, P0222, P0223, P0335, P0336, P0351-P0358, P0562, P0563, P0601-P0604, P0607, P062F, P0633, P0685, P0690, P1631, P1682, or P2610 is not set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Ignition ON, test the fuses that are supplied ignition 1 voltage by the powertrain relay. The test lamp should illuminate ON for each test point of the fuses.
• If the test lamp does not illuminate ON for at least one test point of each fuse, refer to DTC P0685, P0689, P0690, or P1682 P0685.
3. Ignition ON, observe the security indicator on the instrument panel cluster. The security indicator should illuminate momentarily and then go out.
• If the security indicator stays ON or is flashing, review the scan tool DTC information for immobilizer system DTCS-Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle. For more information concerning the immobilizer system, refer to Immobilizer Description and Operation Immobilizer
4. Crank the engine while observing 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.
5. Disconnect the B75B mass airflow (MAF) sensor. Attempt to start the engine. The engine control module will ignore mass airflow sensor input, default to calculated airflow, and the engine should start and run if the mass airflow sensor is faulted.
• If the engine starts and runs, and the mass airflow sensor circuits test OK, replace the B75B mass airflow (MAF) sensor.
6. Install a J 26792 - HEI Spark Tester onto one T8 ignition module/coil assembly on each bank of the engine.
Note: An erratic or weak spark is considered a no spark condition.
7. Crank the engine while observing both spark plug testers. Both spark plug testers should spark.
• If spark is not observed, is inconsistent or weak on either spark plug tester, refer to Electronic Ignition System Diagnosis Electronic Ignition (EI) System Diagnosis.
8. Ignition OFF and all accessories OFF, install the J 37287 - adapters and CH 48027 - gauge. Refer to Fuel Pressure Gauge Installation and Removal Fuel Pressure Gauge Installation and Removal
9. Ignition ON, command the fuel pump ON with a scan tool and observe the fuel pressure. Verify the fuel pressure is between 380-520 kPa (55-76 psi) while the fuel pump is running.
• If the fuel pump does not run, refer to Fuel Pump Electrical Circuit Diagnosis (Without Super Charger) Fuel Pump Electrical Circuit Diagnosis (Without Super Charger)Fuel Pump Electrical Circuit Diagnosis (With Super Charger) Fuel Pump Electrical Circuit Diagnosis (With Super Charger).
• If the fuel pump runs but the fuel pressure is not within the specified value, refer to Fuel System Diagnosis (Without Super Charger) Fuel System Diagnosis (Without Super Charger)Fuel System Diagnosis (With Super Charger) Fuel System Diagnosis (With Super Charger).
10. Verify that the fuel pressure does not decrease greater than 34 kPa (5 psi) in 1 min.
• If the fuel pressure is not within the specified value, refer to Fuel System Diagnosis (Without Super Charger) Fuel System Diagnosis (Without Super Charger)Fuel System Diagnosis (With Super Charger) Fuel System Diagnosis (With Super Charger).
11. Verify the following conditions do not exist:
* Restricted air filter element or air intake system
* Spark plugs for being gas or coolant fouled-Refer to Spark Plug Inspection Testing and Inspection
* A skewed manifold absolute pressure (MAP) sensor-Refer to DTC P0106 (Supercharger) Powertrain Management (Supercharger)DTC P0106 (Without Supercharger) Powertrain Management (Without Supercharger).
* A skewed engine coolant temperature (ECT) sensor-Refer to DTC P0116 P0116.
* Exhaust system restricted-Refer to Restricted Exhaust Restricted Exhaust.
* Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis Testing and Inspection.
* Engine mechanical condition, for example, worn timing chain, sprocket gears, low compression, etc.-Refer to Symptoms - Engine Mechanical Symptoms - Engine Mechanical and Timing Chain, Crankshaft Sprocket, Camshaft Position Actuator, and Solenoid Valve Replacement (L99) Service and Repair.
• If any of the above conditions exist, repair as necessary.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.