GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1996 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 4.3L (Caprice Only) and 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 Symptoms , Important Preliminary Checks Before Starting.
    • Check PCM grounds for being clean, tight and in their proper locations. Refer to PCM wiring diagrams in Electrical Diagnosis.
    • Search for bulletins.

Sensor/System
    • Check Engine Coolant Temperature (ECT) sensor for being shifted in value. Connect a Scan Tool and compare Engine Coolant Temperature with Intake Air Temperature on a cold engine. The ECT and IAT should be within ± 3°C (5°F) of each other. Check the resistance of the ECT sensor if the temperature is out of range with the IAT sensor. Refer to Engine coolant temperature sensor resistance table for resistance specifications. Replace ECT sensor if the resistance is not within the specification. If the sensor is within the specification, repair ECT signal circuit for high resistance.
    • Check Mass Air Flow sensor installation. A MAF sensor that is installed in the wrong direction, may cause a hard start. Important: Embossed arrows on the MAF sensor indicate air flow and must point toward the engine. Install MAF in the proper direction. Refer to Mass Airflow Sensor Replacement , On-Vehicle Service.
    • Using a Scan Tool, monitor TP sensor voltage. The TP sensor voltage should be less then 0.9 volt. If the TP sensor voltage is greater than 0.9 volt, inspect the ASR/TCS adjuster assembly (If so equipped). Also inspect throttle body and accelerator cables for binding. Refer to Adjuster Assembly Throttle And Cruise Control Cables.
    • Check the EGR system for proper operation.

Fuel System
    • Check fuel pump relay operation - pump should turn ON for 2 seconds when ignition is turned ON. Refer to Fuel Pump Electrical Circuit Diagnosis .
    • A faulty in-tank fuel pump check valve will allow the fuel in the lines to drain back to the tank after engine is stopped. To check for this condition, refer to Fuel System Diagnosis
    • Check both injector fuses for being open. An open injector fuse will cause four injectors not to operate. Replace fuse and inspect injector circuits for an intermittent short to ground.
    • Check for low fuel pressure. Refer to Fuel System Diagnosis
    • Check for restricted fuel filter. Refer to Fuel System Diagnosis
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Test

Ignition System
    • Check for proper ignition voltage output with spark tester J 26792. Refer to Distributor Ignition (DI) System Check .
    • Remove spark plugs and check for the following:
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
    • Refer to Spark Plug Replacement.
    • If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
    • Check for bare or shorted ignition wires. Refer to Ignition Wire Replacement.
    • Check for loose ignition coil ground. Refer to Distributor Ignition (DI) System Check .
    • Spark plugs for proper heat range. Refer to Owners Manual or Section OB.
    • Check distributor vent system for being restricted or open. Refer to Distributor Vent System Check .

Engine Mechanical
    • Excessive oil in combustion chamber-Leaking valve seals. Refer to Engine Mechanical.
    • Low cylinder compression. Refer to Engine Mechanical.
    • Combustion chambers for excessive carbon buildup. Clean using Top engine cleaner. Follow instructions on can.
    • For incorrect basic engine parts. Inspect the following:
       - Cylinder heads
       - Camshaft
       - Pistons, etc.

Refer to Engine Mechanical.

Additional Checks

Using a scan tool, check IAC operation.