Engine Cranks But Does Not Run
Diagnostic Instructions
Circuit/System Description
The Engine Cranks but Does Not Run diagnostic table is an organised approach to identifying a condition that causes an engine not to start. This diagnostic directs the service technician to the appropriate system diagnosis.
Diagnostic Aids
Inspect for any of the following conditions:
• | 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 System Diagnosis . |
• | 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. |
• | Inspect the engine for good secure electrical grounds. |
• | 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 workshop. The malfunction may not recur until parked overnight in freezing temperatures. Extreme weather conditions can cause contaminated fuel to prevent the vehicle from starting. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Scan Tool Reference
Control Module References
Special Tools
EN 34730-1A Fuel Pressure Gauge
For equivalent regional tools, refer to Special Tools .
Circuit/System Verification
Note: This diagnostic assumes the following:
• | The engine cranking speed should be at least 100 RPM cold and 180 RPM hot. Refer to Engine Cranks Slowly . |
• | There is adequate fuel in the fuel tank. |
- Engine cranking for 15 s, observe the DTC information with a scan tool. Verify that no DTC is set.
- Visually inspect the fuel system from the high pressure pump to the fuel tank for leaks.
- Engine cranking for 15 s, observe the scan tool Fuel Rail Pressure Sensor parameter. The reading should be greater than 20 MPa (2 900 PSI)
- Verify the following conditions do not exist:
• | Collapsed air inlet duct to the throttle body |
• | Restricted air filter element |
⇒ | If you find any of the above conditions, repair as necessary. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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