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 .
- 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 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 less than 1,000 ohms per 31 cm (per foot). Replace the spark plug wire if more than the specified value. 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
- 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, with a scan tool, observe the 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 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.