Engine Cranks But Does Not Run

Engine Cranks but Does Not Run

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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 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.

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

Special Tools

* CH-48027 Digital Pressure Gage
* J 26792 HEI Spark Tester

Circuit/System Verification

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

Circuit/System Testing

1. Crank the engine for up to 30 seconds.
2. Observe the vehicle DTC information with a scan tool.

^ If any of the following DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose those DTCs: P0016, P0201-P0206, P0230, P0335, P0336, P0351-P0353, P0601, P0602, P0604, P0606, P0685, P0689, P0690, P1516, P2610. Diagnostic Trouble Code Descriptions

3. Ignition OFF for 90 seconds, determine the current vehicle testing altitude. Ignition ON, observe the scan tool MAP Sensor parameter. Compare the parameter to the Altitude Versus Barometric Pressure table. The MAP Sensor Pressure parameter should be within the specified range indicated in the table.

^ If the reading is not correct for your altitude, diagnose the MAP sensor. Refer to DTC P0106. P0106

4. Verify the following scan tool parameters indicate OK when the engine is cranked:

* Cylinder 1-6 Injector Circuit Short to Ground Test Status
* Cylinder 1-6 Injector Circuit Open Test Status

^ If the parameters do not indicate the specified values, refer to DTC P0201, P0202, P0203, P0204, P0205, or P0206. P0201

5. Verify the following scan tool parameters change from Not Run to OK, when the engine is cranked:
Cylinder 1-6 Injector Circuit Short to Volts Test Status

^ If the parameters do not indicate the specified values, refer to DTC P0201, P0202, P0203, P0204, P0205, or P0206. P0201

6. Observe the engine speed parameter while cranking the engine.

^ If engine RPM is not indicated, refer to DTC P0335. P0335

7. Install a J 26792 HEI Spark Tester.
8. Crank the engine for 15 seconds. Spark should be observed from the J 26792 HEI Spark Tester.

^ If spark is not observed refer to Electronic Ignition (EI) System Diagnosis. Electronic Ignition (EI) System Diagnosis

9. With the ignition ON and the engine OFF, test the fuses that are supplied by the powertrain relay for voltage.

^ If the test lamp does not illuminate on at least one side of each fuse, refer to DTC P0685, P0689, or P0690. P0685

Important: Additional DTCs may set when using the fuel pump output control.

10. Command the fuel pump ON and OFF. Fuel pump should energize when commanded ON and De-energize when commanded OFF.

^ If the fuel pump does not respond refer to Fuel Pump Electrical Circuit Diagnosis. Component Tests and General Diagnostics

11. Turn OFF the ignition.
12. Install the CH-48027. Turn ON the ignition and command the fuel pump ON while observing the CH-48027. The fuel pressure should be between 384-425 kPa (56-62 psi).

^ If the fuel pressure is not within 384-425 kPa (56-62 psi) refer to Fuel System Diagnosis. Component Tests and General Diagnostics

13. Inspect for the following conditions:

* Compare the actual engine coolant temperature to the ECT parameter.
* Air filter and air intake system for restrictions and obstructions
* Test the fuel for ethanol content.
* Test the fuel for contamination.
* Inspect the spark plug and spark plug wires.
* Test the exhaust system for restrictions.

Repair Instructions

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

* Spark Plug Inspection
* Spark Plug Wire Replacement