Engine Cranks But Does Not Run. Chevrolet Cobalt 2008

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2008 🢒 Cobalt 🢒 Engine 🢒 Engine Electrical 🢒 Engine Cranks But Does Not Run

Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

This Engine Cranks but Does Not Run diagnostic 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

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 Injector 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 (CKP) 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.

•	If the engine almost starts and then stalls, check for an open in the ground circuits of the CKP sensor and the camshaft position (CMP) sensor.

•

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 minutes 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

Connector End View Reference

Component Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

•	CH-48027-100 Digital Pressure Gage

•	J 26792 (SA91992) Spark Tester

•	J 43244 Relay Puller Pliers

Circuit/System Verification

Important: This diagnostic assumes the following:

•	The battery is completely charged. Refer to Battery Inspection/Test.

•	The engine cranking speed is acceptable. Refer to Engine Cranks Slowly.

•	There is adequate fuel in the fuel tank.

Crank the engine for 15 seconds. Observe the DTC information with a scan tool. The following DTCs should not be set:

DTC P0016, P0017, P0201-P0204, P0230, P0335, P0336, P0351-P0354, P0601, P0602, P0603, P0604, P0606, P0607, P060D, P062F, P0685, P0690, P1516, P1682, P2610.

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

Ignition ON, observe the VTD Fuel Disable parameter with a scan tool. The parameter should display Inactive.

⇒	If Active is displayed, refer to Symptoms - Engine Controls.

Ignition OFF, disconnect the fuel pump relay using the J 43244 .
Connect a J 26792 (SA91992) to the boot of an ignition coil of a cylinder and ground.

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

While cranking the engine, verify that the spark tester sparks.

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

Ignition OFF, install the fuel pump relay.
Ignition ON, command the fuel pump ON with a scan tool. You should hear the fuel pump turn ON.

⇒	If the fuel pump does not turn ON, refer to Fuel Pump Electrical Circuit Diagnosis.

Ignition OFF, install the CH-48027 or CH-48027-100 . Refer to Fuel Pressure Gage Installation and Removal.

Important:

•	The fuel pump may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure.

•	Do NOT start the engine for this test.

Ignition ON, command the fuel pump ON with a scan tool. The fuel pressure should be between 345-414 kPa (50-60 psi).

⇒	If the fuel pressure is not within the specified range, refer to Fuel System Diagnosis.

Verify that the following conditions do not exist:

•	Collapsed air intake duct to the throttle body

•	Restricted air filter element

•	Spark plugs for being gas or coolant fouled

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

•	A skewed engine coolant temperature (ECT) sensor--Refer to Temperature Versus Resistance.

•	Exhaust system restricted--Refer to Restricted Exhaust.

•	Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis.

•	Engine mechanical condition, for example, worn timing belt or low compression--Refer to Symptoms - Engine Mechanical or Engine Compression Test.

⇒	If you find any of the above conditions, repair as necessary.