Diagnostic Instructions
Circuit/System Description
The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic table directs the service technician to the appropriate system diagnosis.
Diagnostic Aids
If the cause of an engine cranks but will not run condition has not been found, inspect for the following conditions:
• | Hard starting only in cold ambient temperatures. These may cause an intermittent condition that may not occur in the service bay: |
- | Fuel heater inoperative |
- | Ice blockage at the fuel pickup in the fuel tank--This will be a high vacuum in the supply lines while cranking, and the problem will disappear after the vehicle is brought in the service bay. It may also exhibit a start and stall condition
or a starting condition with no acceleration. |
• | The correct cranking speed is 100 RPM cold and 180 RPM hot. |
• | Low engine coolant may cause the engine to shut down. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
Important: This diagnostic assumes the following:
• | There is adequate fuel in the fuel tanks. |
- If any DTCs are set diagnose those DTCs first.
- The engine starts and runs.
⇒ | If the engine does not start and run perform the Circuit/System Testing. |
Circuit/System Testing
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
- Turn OFF the ignition for 1 minute, then crank over the engine for 15 seconds. Monitor the DTCs with a scan tool. If DTCs are set, diagnose those DTCs first.
- Inspect for the following conditions:
• | A plugged air filter or collapsed air intake duct |
- Observe the actual fuel rail pressure parameter with a scan tool. The value should be 0 MPa with the ignition ON, engine OFF.
⇒ | If the pressure difference between the actual and desired pressure are more than 2 MPa, replace the fuel pressure sensor. |
- Observe the Actual Fuel Rail Pressure parameter with a scan tool with the ignition ON and engine OFF. Wait 1 minute. The value should be 0 MPa with the ignition ON, engine OFF. If the actual fuel rail pressure is more than 2 MPa,
replace the fuel rail pressure sensor.
- Observe the Actual Fuel Rail Pressure AND Desired Fuel Rail Pressure parameters with a scan tool while cranking the engine. The parameters should be within 2 MPa of each other.
⇒ | If the pressure difference between the actual and desired pressure are more than 2 MPa , inspect for a fuel filter restriction, air being introduced into the fuel lines from the tank to the fuel supply pump or kinked fuel lines. |
⇒ | If there is no condition from the fuel tank to the fuel supply pump, replace the fuel injection supply pump. |
- Inspect for nominal readings at key-up or cranking, where denoted, for the following parameters. Use the Engine Control Module Scan Tool Information, LF8, list or a known good vehicle to determine nominal values.
• | Camshaft and crankshaft signal present, during crank |
• | Barometric pressure, at key-up |
• | Engine coolant temperature, at key-up |
• | Turbocharger boost pressure, at key-up |
| Diagnose and repair sensors or sensor circuits, as necessary. |
- Other possible causes for a no-start condition:
• | Heavily restricted exhaust, plugged exhaust filter or catalytic converter |
• | Poor engine compression |
• | Water or gasoline in fuel system |
• | Engine mechanical timing |
• | Flywheel incorrectly installed or too much crankshaft end-play causing No Crankshaft Present signal on the scan tool |
| Diagnose and repair, as necessary. If everything tests OK, replace the ECM. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.