GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC Sierra Denali 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 Hard Start

Inspection/Test

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 Inspections Before Beginning in Symptoms - Engine Controls .
    • Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics .
    • Search for bulletins.
    • Verify that the driver is using the correct starting procedure as described in the owners manual.

Sensor/System
    • Inspect the idle air control (IAC) system. Refer to Idle Air Control (IAC) System Diagnosis .
    • Inspect for an engine coolant temperature (ECT) sensor that has shifted in value . Refer to Temperature Versus Resistance .
    • Test for proper operation of the throttle position (TP) sensor. Refer to DTC P0121 .
    • Test for proper operation of the manifold absolute pressure (MAP) sensor. Refer to DTC P0106 .

Fuel System
    • Verify there is adequate fuel .
    • Inspect the fuel pump operation. The fuel pump should turn ON for 2 seconds when you turn ON the ignition. Refer to Fuel Pump Electrical Circuit Diagnosis .
    • A faulty in-tank fuel pump check valve allows the fuel in the lines to drain back to the tank after the engine stops. Refer to Fuel System Diagnosis .
    • Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Ignition System
    • In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures:
       -  Spark Plug Inspection
       -  Spark Plug Replacement
    • Remove spark plugs and inspect for the following:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Spark plugs are of the correct type.
    • Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester .
    • An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool.
    • If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs.
    • Inspect the distributor. Refer to Distributor Inspection .
    • Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection .

Engine Mechanical

Inspect for the following conditions:

    • Excessive oil in combustion chamber or leaking valve seals--Refer to Oil Consumption Diagnosis .
    • Low cylinder compression--Refer to Engine Compression Test .
    • Bent pushrods
    • Improper valve timing
    • Worn rocker arms
    • Broken or worn valve springs
    • Combustion chambers for excessive carbon buildup--Clean the chambers using top engine cleaner. Follow the instructions on the can.
    • Incorrect, worn, or damaged basic engine parts--Inspect the following:
       - The camshaft--Refer to Camshaft and Bearings Cleaning and Inspection .
       - The cylinder heads--Refer to Cylinder Head Cleaning and Inspection .
       - The pistons, etc.--Refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection .
    • Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearing Cleaning and Inspection . This could result in any of the following conditions:
       - A no start
       - A start and stall
       - Erratic performance

Additional
    • Inspect for a restricted exhaust. Refer to Restricted Exhaust .
    • Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking.