Circuit/System Testing
- Verify that the following conditions do not exist:
- Vacuum hose splits, kinks, and incorrect connections
- Engine vacuum leaks
- Crankcase ventilation system for vacuum leaks
- Fuel pressure that is too low or too high-Refer to Fuel System Diagnosis .
- Contaminated fuel-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Restricted exhaust system-Refer to Restricted Exhaust .
- If you find any of the above conditions, repair as necessary.
- Ignition OFF, disconnect the spark plug wire from the misfiring cylinder.
- Install the J 26792 to the boot of a spark plug wire and ground.
- Attempt to start the engine and observe the J 26792
. The spark tester should spark.
- If there is no spark, test the spark plug wire for the correct resistance. Refer to Ignition System Specifications. Replace the spark plug wire if necessary. If the spark plug wire test normal, refer to Electronic Ignition (EI) System Diagnosis for diagnosis of the ignition coil.
- Ignition OFF, remove the spark plug from the misfiring cylinder. Verify that the following conditions do not exist with the spark plug:
- Gas, coolant, or oil fouled-Refer to Spark Plug Inspection .
- Cracked, worn, incorrectly gapped
- If there is a condition with the spark plug, replace the spark plug.
- Exchange the suspected spark plug with another cylinder that is operating correctly.
- Engine idling, observe the Misfire Current Counters with a scan tool. The misfire should not follow the spark plug exchange.
- If the misfire follows the spark plug, replace the spark plug.
- If all conditions test normal, test or inspect for the following:
- A lean or rich fuel injector-Refer to Fuel Injector Solenoid Coil Test
- An engine mechanical condition-Refer to Symptoms - Engine Mechanical
IMPORTANT:
An erratic or weak spark is considered a no spark condition.