Engine Cranks But Does Not Start

Engine Cranks But Does Not Start

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 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

* 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 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 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.

* 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.

* The engine control module (ECM) uses the camshaft position sensors to determine engine speed and position when there is a crankshaft position sensor condition. If a crankshaft position sensor condition exists, the engine will operate only if the ECM has stored the learned reference position of the camshafts in ECM memory. With a crankshaft position 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 camshaft position sensors.

* Inspect the engine for good secure electrical grounds.

* The fuel pump control module controls and monitors the operation of the in-tank fuel pump. If the fuel pump control module detects a fault, a DTC sets in the fuel pump control module. The fuel pump control module will then send a serial data message to the engine control module (ECM) requesting the illumination of the malfunction indicator lamp (MIL).

* 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 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.

Reference Information

Schematic Reference

Engine Controls Schematics (LEA) [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (MN5)

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

* Starting System Description and Operation Description and Operation

Scan Tool Reference

Control Module References Programming and Relearning for scan tool information

Special Tools

* CH-48027 - Digital Pressure Gauge

* J 26792 - HEI Spark Tester

Circuit/System Verification

Note: This diagnostic assumes the following:

* The battery is completely charged. See Battery Inspection/Test Battery Inspection/Test.

* The engine cranking speed is acceptable. refer to Engine Cranks Slowly Testing and Inspection.

* There is adequate fuel in the fuel tank.

1. Engine cranking, observe the scan tool DTC information. The following DTCs should not be set:
P0201-P0204, P0230, P0231, P0232, P023F, P025A, P0335, P0336, P0351-P0354, P0601, P0602, P0603, P0604, P0606, P0607, P060E, P062F, P0685, P0689, P0690, P069E, P1516, P1682, P2610, P2635.

• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. 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 additional information, refer to Immobilizer Description and Operation Immobilizer.

3. Engine cranking, observe the scan tool Engine Speed parameter. The scan tool should indicate an engine speed greater than 0 RPM

• If engine speed is 0 RPM, refer to DTC P0335 or P0336 P0335 for further diagnosis.

4. Ignition OFF, disconnect the T8 ignition coil from the cylinder and spark plug.

5. Connect a J 26792 - HEI Spark Tester between the boot of an ignition coil and ground.

Note: An erratic or weak spark is considered a no spark condition.

6. Engine cranking, verify that the spark tester sparks.

• If there is no spark, refer to Electronic Ignition System Diagnosis Electronic Ignition (EI) System Diagnosis.

7. Ignition ON, engine OFF, command the scan tool Fuel Pump Enable ON and OFF to verify the G12 fuel pump runs.

• If the G12 fuel pump does not turn ON and OFF, or does not run, refer to Fuel Pump Electrical Circuit Diagnosis Fuel Pump Electrical Circuit Diagnosis.

8. Perform the Fuel System Diagnosis Fuel System Diagnosis to verify proper G12 fuel pump operation and fuel pressure.

9. Verify the following conditions do not exist:

* Collapsed or restricted air intake duct to the throttle body

* Restricted air filter

* Gas or coolant fouled spark plugs

* A skewed manifold absolute pressure (MAP) sensor. Refer to DTC P0106 P0106.

* A skewed engine coolant temperature (ECT) sensor. Refer to DTC P0116 P0116.

* A restricted exhaust system. Refer to Restricted Exhaust Restricted Exhaust.

* Contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis Testing and Inspection.

* An engine mechanical condition, for example, worn timing chain and gears or low compression. Refer to Symptoms - Engine Mechanical Symptoms - Engine Mechanical
and Engine Compression Test Testing and Inspection.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

Spark Plug Replacement Service and Repair