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	Test 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 Air Flow (MAF) Sensor Replacement . The Camshaft Position Sensor (CMP) may cause a long engine crank time if the PCM does not receive a CMP signal. Test the exhaust system for a restriction. Refer to Restricted Exhaust .
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 faulty in-tank fuel pump check valve 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	Inspect both injector fuses for being open. An open injector fuse causes four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuits and the injector circuits for an intermittent short to ground. Inspect 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: Correct heat range; refer to Spark Plug Usage in Engine Electrical. Wet plugs Cracks Wear Improper gap Burned electrodes 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 fouled, refer to DTC P0172 Fuel Trim System Rich Bank 1 or DTC P0175 Fuel Trim System Rich Bank 2 . If the spark plugs are coolant or oil fouled, refer to Oil Consumption Diagnosis in Engine Mechanical-5.7L or Loss of Coolant in Engine Cooling. Inspect for bare or shorted ignition wires. Refer to Spark Plug Wire Resistance 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-5.7L. Test for low cylinder compression. Refer to Engine Compression Test in Engine Mechanical-5.7L. 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: Cylinder heads Camshaft Pistons, etc. Refer to Engine Mechanical-5.7L.