GM Service Manual Online
For 1990-2009 cars only

Inspection/Test

Action

DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately stalls.

Preliminary

    •  Refer to Intermittent Conditions before starting.
    •  Search for bulletins.

Sensor/System

    • Test engine coolant temperature (ECT) sensor for being shifted in value. Connect a scan tool and compare engine coolant temperature with intake air temperature (IAT) on a cold engine. The ECT and IAT should be within ± 3°C (5°F) of each other. Test the resistance of the ECT sensor if the temperature is out of range with the IAT sensor. Refer to Temperature Versus Resistance . If the ECT sensor resistance is not within the specification, refer to DTC P0117 or DTC P0113 .
    •  Monitor the 24X crank sensor and the CMP sensor signal present parameters on a scan tool. If both are not responding, test the sensor feed circuit. Both sensors use a separate feed circuit but are internally connected to power. Test all CKP sensor A and CMP sensor circuits for intermittents. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    •  Monitor the 3X crank sensor parameter on the scan tool. If the 3X crank sensor parameter is not responding, inspect the CKP sensor B and circuits for intermittents. Inspect the ignition control (IC) circuit, IC timing control circuit, low resolution engine speed signal circuit and the low reference circuit for intermittents. If these circuits become open, or shorted, they may not set a DTC immediately, but are capable of causing driveability complaints. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    •  Inspect the mass air flow (MAF) sensor for proper installation and conditions. A MAF sensor with a damaged honeycomb may cause a hard start.
    •  Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking, especially between the MAF sensor and the throttle body.
    •  Using a scan tool, test idle air control (IAC) operation. Command the engine RPM to 1,500 and back to the starting RPM. If the engine RPM does not change when commanded, refer to DTC P0506 and DTC P0507 to diagnose the IAC system.
    •  Inspect the exhaust gas recirculation (EGR) system for proper sealing/connections and operation. Refer to Exhaust Gas Recirculation (EGR) System Description .

Fuel System

    •  Test the fuel system circuits for proper operation. Refer to Fuel Pump Electrical Circuit Diagnosis .
    •  Test for low fuel pressure. Refer to Fuel System Diagnosis .
    •  Test for faulty fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , Fuel Injector Solenoid Coil Test test procedures.
    •  Inspect for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Ignition System

    • Inspect for proper ignition voltage output using the following steps:
        1. Attach the J 26792 Spark Tester to engine ground.
        2. Connect the spark plug end of the spark plug wire to the J 26792 . Leave the other end of the spark plug wire connected to the coil being tested.
        3. Connect the spark plug end of the companion spark plug wire to ground. The companion spark plug wire is the wire attached to the corresponding coil tower.
        4. Crank the engine while observing the J 26792 . A spark should be observed.
        5. Repeat the above steps for each coil.
    •  If spark is not present at the coils, inspect for the following conditions:
       -  Coils--Cracks, carbon tracking/arcing, or a resistance value outside the specified range

Coil Resistance
5000-8000 ohms (5K-8K ohms)

       -  Spark plug wires--Signs of arcing, cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range

Spark Plug Wire Resistance
9840 ohms per meter (3000 ohms per foot)

    Important: :  Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. Ignition voltage will arc to ground when a secondary component is faulty.

       -  Defective ignition module
       -  Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring
    •  Remove spark plugs and inspect for the following conditions:
       -  Fouled plugs
       -  Cracks
       -  Wear
       -  Improper gap
       -  Burned or damaged electrodes
       -  Improper heat range or reach
    •  If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. Refer to Spark Plug Inspection .

Engine Mechanical

    •  Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
    •  Low cylinder compression--Refer to Engine Compression Test in Engine Mechanical.
    •  For incorrect basic engine parts--Inspect the following conditions:
       -  Cylinder heads
       -  Camshaft and valve train components
       -  Pistons, etc.