GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 Hard Start

Checks

Action

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

Preliminary
    • Refer to Important Preliminary Checks Before Starting in Symptoms .
    • Inspect the PCM grounds for being clean, tight and in the proper locations. Refer to Engine Controls Schematics .
    • Search for bulletins.

Sensor/System
    • Check the operation of the Column Lock System. Refer to Diagnostic System Check - Body Control System in Body Control System.
    • Inspect the Engine Coolant Temperature (ECT) sensor for being shifted in value. Connect a scan tool. Compare the Engine Coolant Temperature against the Intake Air Temperature (IAT) on a cold engine. The ECT and IAT sensor values should be within ± 3°C (5°F) of each other. If the ECT sensor is out of range with the IAT sensor, test the resistance of the ECT sensor. Refer to Temperature vs Resistance for resistance specifications. Replace the ECT sensor if the resistance is not within the specification. If the sensor is within the specification, repair ECT signal circuit for high resistance.
    • Inspect the Mass Air Flow sensor installation. A MAF sensor that is incorrectly installed may cause a hard start. Important: The embossed arrows on the MAF sensor indicate the direction of the intake air flow. The arrows must point toward the engine. Install the MAF in the proper direction. Refer to Mass Airflow Sensor Replacement .
    • Test the Camshaft Position Sensor (CMP) performance. A long engine crank time occurs if the PCM does not receive a CMP signal.

Fuel System
    • Test the fuel pump relay operation. The fuel pump should turn ON for 2 seconds when you turn on the ignition. Refer to Fuel Pump Electrical Circuit Diagnosis .
    • A malfunctioning check valve in the fuel feed rear pipe allows the fuel in the lines to drain back to the tank after the engine stops. To test for this condition, refer to Fuel System Diagnosis .
    • Inspect both injector fuses for being open. An open injector fuse causes four injectors and four ignition coils not to operate. Replace the fuse. Inspect the injector circuits and the ignition coil circuits for an intermittent short to ground.
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Ignition System
    • Test for proper ignition voltage output with spark tester J 26792 . Refer to Electronic Ignition (EI) System Diagnosis .
    • Remove the spark plugs and inspect for the following conditions:
       - Correct heat range; refer to Spark Plug Usage in Engine Electrical.
       - Wet plugs; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Cracks; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Wear; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Improper gap; refer to Spark Plug Replacement in Engine Electrical.
       - Burned electrodes; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Heavy deposits; refer to Spark Plug Visual Diagnosis in Engine Electrical.
    • Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to DTC P0172 Fuel Trim System Rich Bank 1 or DTC P0175 Fuel Trim System Rich Bank 2 for diagnosis of the rich condition. Refer to Spark Plug Visual Diagnosis in Engine Electrical for diagnosis of coolant or oil fouled spark plugs.
    • Inspect for bare or shorted ignition wires. Refer to Spark Plug Wires Not Operating Properly in Engine Electrical.
    • Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .

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.
    • Combustion chambers for excessive carbon buildup. Clean the chambers using top engine cleaner. Follow the instructions on the can.
    • For incorrect basic engine parts. Inspect the following:
       - The cylinder heads
       - The camshaft
       - The pistons, etc.

Refer to Engine Mechanical.