GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Century 🢒 Engine 🢒 Engine Controls - 3.1L (LG8) 🢒 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 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 ECT 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 the Temperature Versus Resistance Table. If the ECT sensor resistance is not within the specification, refer to DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage or DTC P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage .
    •  Monitor the 24X Crankshaft Position and Camshaft Position Sensors on 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 24X and CMP sensor circuits for intermittents. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    •  Monitor the 3X parameter on the scan tool. If the 3X is not responding, inspect the 7X CKP Sensor and circuits for intermittents. Inspect the IC circuit, Bypass circuit, 3X Reference High Circuit, and the 3X Reference Low circuit for intermittents. If these circuits become open, or shorted 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.
    •  Test mass air flow sensor for proper installation and conditions. A MAF sensor with a damaged honeycomb may cause a hard start. Refer to Information Sensors/Switches Description .
         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 the IAC operation. Refer to Idle Air Control (IAC) System Diagnosis .
    •  Inspect the EGR system for proper sealing/connections and operation.

Fuel System
    • Test the fuel pump relay circuit for proper operation. Refer to Fuel Pump Electrical Circuit Diagnosis .
    • Test for low fuel pressure. Refer to Fuel System Pressure Test .
    •  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 spark tester; 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 spark tester; 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
5000-8000ohms (5K-8Kohms)

       -  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
600ohms per foot (1 968ohms per meter).

    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.

Engine Mechanical
    • Inspect for the following conditions:
       - Excessive oil in combustion chamber or leaking valve seals--Refer to Engine Noise Diagnosis in Engine Mechanical.
       -  Low cylinder compression-- Refer to Engine Compression Test in Engine Mechanical.
    •  For incorrect basic engine parts, inspect the following components:
       -  Cylinder heads
       -  Camshaft and valve train components
       -  Pistons, etc.
    • For more diagnostic aids refer to Base Engine Misfire Diagnosis in Engine Mechanical.