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Makes 🢒 Pontiac 🢒 2008 🢒 Torrent 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 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

This Engine Cranks but Does Not Run diagnostic is an organized approach to identify a condition which causes the engine to crank but not start. This diagnostic directs the technician to the appropriate system diagnosis.

Diagnostic Aids

Inspect for any of the following conditions:

    • The engine control module (ECM) uses the camshaft position (CMP) sensors to determine engine speed and position when there is a crankshaft position (CKP) sensor condition.
    • The engine will operate with a CKP sensor condition only if the ECM has stored the learned reference position of the camshafts in memory. With a CKP sensor condition in the signal circuit, the engine will go into a limp home mode after a hard restart. The ECM then calculates engine speed from one of the CMP sensors.
    • 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 Solenoid Coil Test.
    • 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 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 CKP 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. The CMP Sensor parameter should display 0 RPM unless P0335, P0336, or P0338 is set indicating a crank sensor fault. The CKP Resync Counter parameter should display zero unless the crank sensor has missed a TDC reference pulse during the current ignition cycle.
    • 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 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 inspect for an engine starting or will not stay running concern.

Reference Information

Schematic Reference

Engine Controls Schematics

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

    •  J 34730-1A Fuel Pressure Gage
    •  J 26792 Spark Tester

Circuit/System Verification

Note: This diagnostic assumes the following:

   • The battery is completely charged. Refer to Battery Inspection/Test.
   • The engine cranking speed is acceptable. Refer to Engine Cranks Slowly.
   • There is adequate fuel in the fuel tank.

  1. Crank or start the engine. Observe the DTC information with a scan tool. Verify that DTC P0116, P0117, P0118, P0119, P0201-P0206, P0335, P0336, P0338, P0351-P0356, P0601, P0602, P0604, P0606, P0627, P0628, P0629, P1629, P1631, P1632, or P2105 is not set.
    2. ⇒If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
  2. Ignition ON, observe the Theft Deterrent parameter with a scan tool. The parameter should display Disabled.
    3. ⇒If Enabled is displayed, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
  3. Test the ignition system for spark. Refer to Electronic Ignition (EI) System Diagnosis.
  4. Ignition ON, command the fuel pump ON with a scan tool. You should hear the fuel pump turn ON.
    5. ⇒If the fuel pump does not turn ON, refer to Fuel Pump Electrical Circuit Diagnosis.
  5. Ignition OFF, install the J 34730-1A . Refer to Fuel Pressure Gage Installation and Removal.

    6. Note: 

       • The fuel pump may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure.
       • Do NOT start the engine for this test.

  6. Ignition ON, command the fuel pump ON with a scan tool. The fuel pressure should be between 380-410 kPa (55-60 psi).
    7. ⇒If not within the specified range, refer to Fuel System Diagnosis.
  7. Verify that the following conditions do not exist:
    8. • Disconnect the MAF sensor. The ECM will ignore the MAF sensor and default to the calculated air flow.
         ⇒If disconnecting the MAF sensor corrects the condition and the connections are OK, replace the MAF sensor. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement.
    • Collapsed air intake duct to the throttle body
    • Restricted air filter element
    • Spark plugs for being gas or coolant fouled--Refer to Spark Plug Inspection.
    • A skewed engine coolant temperature (ECT) sensor--Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor.
    • Exhaust system restricted--Refer to Restricted Exhaust.
    • Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
    • Engine mechanical condition, for example, worn timing chain and gears, low compression--Refer to Symptoms - Engine Mechanical.
         ⇒If you find any of the above conditions, repair as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.