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Engine Cranks But Does Not Run

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

Circuit/System Description

The engine cranks but does not run is an organised approach to identify a condition which causes the engine to crank but not start. This diagnostic directs the technician to the appropriate system diagnosis.

This diagnostic assumes the system voltage levels are adequate for starter motor operation. Fuel level and fuel quality must be determined for correct diagnosis.

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. Refer to Fuel Injector Diagnosis with Special 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 vehicle in good condition.
    • Check the crankshaft position sensor engine reference signal with a scan tool. 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 circuit 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 min in a heated workshop. 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 garage 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.

Reference Information

Schematic Reference

Engine Controls Schematics : Siemens ECM - LPG with LCP → Siemens ECM - Gas without FX3 or LCP → Delphi ECM - FX3

Connector End View Reference

Component Connector End Views

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information

Special Tools

    • CH 48027 Digital Pressure Gauge
    • EL 26792 HEI Spark Tester
    • J 34730-405 Injector Test Lamp

For equivalent regional tools, refer to Special Tools .

Circuit/System Verification

Attempt to start the engine. The engine should start and run.

Circuit/System Testing
  1. Crank the engine for up to 15 s.
  2. Verify that other DTCs are not set.
    3. ⇒If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  3. Ignition ON, verify that the theft deterrent LED located in the instrument cluster is OFF.
    4. ⇒If the LED is ON, or blinking, refer to Symptoms - Theft Deterrent .
  4. Ignition OFF for 90 s, determine the current vehicle testing altitude. Ignition ON, verify that the scan tool manifold absolute pressure (MAP) sensor parameter is within the specified range indicated in the Altitude Versus Barometric Pressure table.
    5. ⇒If not within the specified range, test the B74 manifold absolute pressure sensor. Refer to DTC P0107 or P0108 : FX3 → Without FX3 .
  5. Ignition OFF, disconnect the harness connector at the fuel injector.
  6. Engine cranking, verify the J 34730-405 injector test lamp flashes between the control circuit and the ignition circuit.
    7. ⇒If the J 34730-405 injector test lamp does not flash, refer to DTC P0261, P0262, P0264, P0265, P0267, P0268, P0270, or P0271 : FX3 → Without FX3 .
  7. Verify the engine speed parameter indicates current engine speed while cranking the engine.
    8. ⇒If engine speed is not indicated, refer to DTC P0335-P0337 : FX3 → Without FX3 .
  8. Install the EL 26792 hei spark tester.
  9. Crank the engine for 15 s, verify that spark is observed from the EL 26792 hei spark tester.
    10. ⇒If spark is not observed, refer to Electronic Ignition System Diagnosis .
  10. Command the fuel pump ON and OFF. Fuel pump should energize when commanded ON and de-energize when commanded OFF.
    11. ⇒If the fuel pump does not respond, refer to Fuel Pump Electrical Circuit Diagnosis .
  11. Turn OFF the ignition.
  12. Install the CH 48027 digital pressure gauge or equivalent. Verify the fuel pressure is 384-425 kPa (56-62 psi) while commanding the fuel pump ON with a scan tool.
    13. ⇒If not within the specified range, refer to Fuel System Diagnosis .
  13. Inspect for the following conditions:
    14. • Compare the actual engine coolant temperature to the ECT parameter.
    • Air filter and air inlet system for restrictions and obstructions
    • Test the fuel for contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect the spark plug. Refer to Spark Plug Inspection .

Repair Verification

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Instrument Cluster Replacement
    •  Spark Plug Replacement
   


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