Circuit/System Testing
- Verify 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 .
- Exhaust system restrictions
- 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 a good 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 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 running, observe the scan tool misfire counters and see if the misfire follows the spark plug that corresponds to the misfiring cylinder.
- If the misfire follows the spark plug, replace the spark plug.
- If the misfire does not follow the spark plug, test the fuel injector. Refer to Fuel Injector Solenoid Coil Test
- If all conditions test normal, test or inspect for the following:
- A lean or rich fuel injector-Refer to Fuel Injector Balance Test with Special Tool
- An engine mechanical condition-Refer to Symptoms - Engine Mechanical
IMPORTANT:
An erratic or weak spark is considered a no spark condition.