Hard to Start

Definition: The engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but immediately dies.

Preliminary Checks

^ Refer to Important Preliminary Checks. Testing and Inspection
^ Make sure the vehicle's operator is using the correct starting procedure.

Sensor Checks

^ Check the Engine Coolant Temperature (ECT) sensor with the scan tool. Compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees greater or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit. Refer to DTC P0125 ECT Excessive Time to Closed Loop. P0125
^ Check the 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 the idle. While monitoring the TP sensor voltage, the scan tool should display less than 0.85 volt with the throttle closed.

Fuel System Checks

Important: A faulty in-tank fuel pump check valve will allow the fuel in the lines to drain back to the tank after the engine stops.

^ Check the fuel pump relay for proper operation. The fuel pump should operate for the first 2 seconds when turning ON the ignition. Refer to Fuel Pump Relay Circuit Diagnosis. Circuit Diagnosis - Fuel Pump Relay
^ Check the fuel pressure. Refer to the Fuel System Pressure Test. System Diagnosis - Fuel System Pressure Test
^ Check for water contamination in the fuel.
^ Perform the fuel injector coil test. Refer to Fuel Injector Coil Test. Fuel Injector Coil Test
^ Perform the fuel injector balance test. Refer to Fuel Injector Balance Test. Fuel Injector Balance Test
^ Check the fuel pump check valve. Refer to the Fuel System Pressure Test. System Diagnosis - Fuel System Pressure Test

Ignition System Checks

^ Check for the proper ignition voltage output with J 26792 or the equivalent.
^ Check the spark plugs for the following conditions:

- Wet plugs
- Cracks
- Wear
- Improper gap
- Burned electrodes
- Heavy deposits

^ Check for bare or shorted ignition wires.
^ Check for moisture in the distributor cap if applicable.
^ Check for loose ignition coil connections.
^ Check for loose Ignition Control Module connections.
^ Check for a faulty Control Module or ignition system grounds.
^ Check the Ignition Control (IC) circuit for an open or short to ground. Refer to Enhanced Ignition System Diagnosis. System Diagnosis - Enhanced Ignition

Important:

1. If the engine starts but then immediately stalls, remove the Crankshaft Position (CKP) sensor.
2. Check for improper resistance or faulty connections.
^ Check the Crankshaft Position (CKP) sensor resistance and connections.

Engine Mechanical Checks

^ Check for the following:

- Improper valve timing
- Low compression
- Bent push rods
- Worn rocker arms
- Broken or weak valve springs
- Worn camshaft lobes

Check the intake and exhaust manifolds for casting flash. Refer to Engine.