Hard to Start

Definition: Engine cranks OK, but does not start for a longtime. Does eventually run, or may start but immediately dies.

PRELIMINARY CHECKS
^ Refer to Important Preliminary Checks. Testing and Inspection
^ Make sure the driver is using the correct starting procedure.
^ Check service bulletins for updates.

SENSORS
CHECK: Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) sensors
- Using a Tech 1 scan tool, compare coolant and intake air temperatures with ambient temperature when engine is cold.
- If coolant or intake air temperature readings are 5 degrees greater than or less than ambient air temperature on a cold engine, check resistance in the ECT/IAT sensor circuit or sensor itself. Compare ECT/IAT resistance value to the "Diagnostic Aid" charts found within DTC 14/23 charts. Refer to Diagnostic Charts/Trouble Code Charts/Code 14 Coolant Temperature Sensor - Diagnostic Aid Powertrain Controls - ECM/PCM
and Diagnostic Charts/Trouble Code Charts/Code 23 Intake Air Temperature Sensor - Diagnostic Aid.
CHECK: Throttle Position (TP) Sensor
- If a sticking throttle shaft or binding linkage causes a high TP sensor voltage (open throttle indication), the control module will not control idle. Monitoring TP sensor voltage. Scan tool and/or voltmeter should display less than 0.85 volt with throttle closed.
CHECK: Manifold Absolute Pressure (MAP) sensor.

FUEL SYSTEM
CHECK: Fuel pump relay operation. Fuel pump should operate for 2 seconds when ignition is turned "ON." Refer to Diagnostic Charts/Chart A-5 Fuel Pump and Relay Electrical Test. Chart A-5 Fuel Pump and Relay Electrical Test
CHECK: Fuel pressure. Diagnostic Charts/Chart A-6 Fuel System Diagnosis Related Tests, Information and Procedures
CHECK: For water contaminated fuel.
CHECK: Injector driver circuit.
- Disconnect all injector harness connectors at the injectors. Connect J 34730-2B Injector Test Light or equivalent 12 volts test light between the harness terminals of each injector connector and note light while cranking. If test light fails to blink at any connector, it is a faulty injector drive circuit harness, connector or terminal. Injector resistance. Measure injector resistance of each injector(s). Nominal resistance of each injector should be 1.16 to 1.36 ohms at 20°C (68°F) for TBI and for CMFI, the resistance is 1.37 to 1.77 ohms. Resistance will increase slightly at higher temperatures.
CHECK: Fuel injector(s).

IMPORTANT
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.

CHECK: Vacuum control valve.
CHECK: Fuel injectors.
- perform injector balance test.

IGNITION SYSTEM
CHECK: Ignition system for:
- Proper ignition voltage output with spark tester J 26792 or equivalent (ST 125).
- Spark plugs; wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
- Bare and shorted wires.
- Moisture in distributor cap.
- Worn distributor shaft.
- Pickup coil resistance and connections.
- Loose ignition coil connections.
- Loose Ignition Control Module (ICM) connections.
- Faulty control module and ignition grounds. Refer to Diagnostic Charts/C Chart/Distributor Ignition System Check. System Check - Distributor Ignition (DI)
CHECK: CKT 423 (Ignition Control) for short to ground.

ENGINE MECHANICAL
CHECK: For proper valve timing, low compression, bent pushrods, worn rocker arms, broken or weak valve springs, worn camshaft lobes.
CHECK: Intake and exhaust manifold passages for casting flash.

ADDITIONAL CHECKS
CHECK: IAC operation - refer to Diagnostic Charts/C Charts/Idle Air Control System Check. System Check - Idle Air Control (IAC )