GM Service Manual Online
For 1990-2009 cars only

Checks

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

Preliminary Checks

Refer to Powertrain On Board Diagnostic (OBD) System Check .

    • Refer to Symptoms .
    • Check that the driver is using the correct starting procedure.

Sensor Checks

    • Inspect for a shifted or fixed engine coolant temperature (ECT) sensor. Test the engine coolant temperature (ECT) sensor. Use a scan tool in order to compare the engine coolant temperature reading on a cold engine with the ambient air temperature reading of the same engine. A coolant temperature reading that is more than 5°C (9°F) different than the ambient air temperature reading on a cold engine may indicate a high resistance in the coolant sensor circuit or in the sensor. Refer to Temperature Versus Resistance .
    • Check the throttle position (TP) sensor. A sticking throttle shaft or a binding throttle linkage will causes a high TP sensor voltage or an open throttle indication. The PCM may not control the idle if a high TP voltage is present. Monitor the TP sensor voltage with the scan tool or a digital multimeter. The indicated voltage should be less than 1.25 volts with the throttle closed.
    • Check the canshaft position (CMP) 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.

Fuel System Checks

    • Check the fuel pump relay for correct operation. The fuel pump should operate for 2 seconds when turning ON the ignition. Refer to Fuel Pump Electrical Circuit Diagnosis .
    • Check for the correct fuel pressure. Refer to Fuel System Diagnosis .
    • Check for water contaminated fuel or inferior quality fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check the operation of the fuel pump check valve. A faulty check valve will allow the fuel in the fuel lines to drain back into the fuel tank after stopping the engine. This condition can cause hard starts, especially on hot soak restarts. In order to check for this condition, perform the fuel pressure check in Fuel System Diagnosis .

Ignition System Checks

    • Check for adequate secondary ignition voltage with a J 26792 spark tester or an equivalent.
    • Check for the correct ignition timing. Refer to Ignition Timing Adjustment .
    • Check the spark plugs for any of the following conditions:
       - Any wet plugs
       - A terminal screw that is bent or loose
       - A ceramic insulator that has cracks, carbon tracking, or deposits
       - A tip insulator that has cracks, carbon tracking, deposits, or that is loose
       - A center electrode that is loose
       - An incorrect spark plug gap that is too large or too small
    • Check for loose ignition coil connections.
    • Check all the ignition system electrical connections.

Additional Checks

    • Check for the correct operation of the idle air control (IAC) system. Refer to Idle Air Control (IAC) System Diagnosis .
    • Check for no crank signal to the PCM. In order to provide improved cold engine starting, the PCM delivers a richer fuel injector pulse on a cold engine when the crank signal is present. Observe the Starter Switch parameter on the scan tool while cranking the engine. A faulty crank signal circuit will NOT cause a no start, only a longer start time under harsh conditions.
    • Check for the correct operation of the EGR valve. Refer to Exhaust Gas Recirculation (EGR) System Diagnosis .
    • Check for service bulletin updates or information.