Engine Cranks But Does Not Run
Engine Cranks But Does Not Run
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.
This diagnostic assumes the system voltage levels are adequate for starter motor operation. Refer to Battery Inspection/Test (Battery Inspection/Test) , and Engine Cranks Slowly (Engine Cranks Slowly). Fuel level and fuel quality should be determined for correct diagnosis.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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
Attempt to start the engine. The engine should start and run.
Circuit/System Testing
1. Crank the engine while observing the scan tool Vehicle DTC Information.
• If any of the following DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) to diagnose those DTCs P0201-P0208, P0230, P0335, P0336, P0340, P0403, P0404, P0601, P0602, P0603, P0604, P0606, P0607, P060D, P062F, P0641, P0651, P0685, P0689, P0690, P1516, P2610.
2. 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 (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).
3. Install a J 26792 HEI Spark Tester.
4. Crank the engine while observing the spark tester. The spark tester should spark.
• If spark is not observed refer to Electronic Ignition System Diagnosis (Electronic Ignition System Diagnosis).
Important: Additional DTCs may set when using the fuel pump output control.
5. 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 System Diagnosis (Fuel System Diagnosis).
6. Turn OFF the ignition.
7. Install the CH-48027 . Turn ON the ignition and command the fuel pump ON while observing the CH-48027 . Refer to Fuel Pressure Gauge Installation and Removal (Fuel Pressure Gauge Installation and Removal). The fuel pressure should be between 384-425 kPa (55-61 psi).
• If the fuel pressure is not within 384-425 kPa (55-61 psi), refer to Fuel System Diagnosis (Fuel System Diagnosis).
8. 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 contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Alcohol/Contaminants-in-Fuel Diagnosis).
* Inspect the spark plugs. Refer to Spark Plug Inspection (Testing and Inspection).
* Test the exhaust system for restrictions. Refer to Restricted Exhaust (Restricted Exhaust).
* Engine mechanical conditions such as worn timing chain gears, low compression, etc.-Refer to Engine Compression Test (Testing and Inspection).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.