- Visually inspect the engine compartment to ensure that all vacuum lines and spark plug wires are properly routed and securely connected.
- Be certain that the battery is fully charged and that all accessories are OFF during the diagnosis.
- Measure the spark plug wire resistance. Please refer to General Information and Maintenance, Routine Maintenance and Tune-Up, Spark Plug Wires, Testing, for this procedure.
A simple way to check for proper ignition system operation is the secondary spark test. If however, this test fails to show a spark, the individual components of the system must be tested. Refer to the different components in this section for their testing procedures.
Primary Circuit Test
To check for the proper primary ignition circuit switching on 1993-98 3.0L engines:
- With the ignition switch OFF , disconnect the coil harness connector from the coil.
Connect a 12 volt test light to the POSITIVE battery terminal. (This is the opposite of the usual test light connection, however, the light is being used to supply voltage to the part of the circuit being checked.)
WARNINGDo not let the test light probe contact any metal parts of the vehicle while it is connected to the positive battery terminal.
- Probe the green wire (pin 2) terminal in the ignition coil harness connector.
- Crank the engine and observe the test light. If the circuit is operating properly, the light should flash rapidly. If not, perform diagnosis of the ignition system using individual component diagnostic procedures.
Secondary Spark Test
The best way to perform this procedure is to use a spark tester (available at most automotive parts stores). Three types of spark testers are commonly available. The neon bulb type is connected to the spark plug wire and flashes with each ignition pulse. The air gap type must be adjusted to the individual spark plug gap specified for the engine. The last type of spark plug tester looks like a spark plug with a grounding clip on the side, but there is no side electrode for the spark to jump to. The last two types of testers allows the user to not only detect the presence of spark, but also the intensity (orange/yellow is weak, blue is strong).
- Disconnect a spark plug wire at the spark plug end.
- Connect the plug wire to the spark tester and ground the tester to an appropriate location on the engine.
- Crank the engine and check for spark at the tester.
- If spark exists at the tester, the ignition system is functioning properly.
- If spark does not exist at the spark plug wire, check the wires, distributor cap, rotor, and ignition coil. If no problem is found, perform the primary circuit test on 1993-98 3.0L engines. On 1999-00 3.3L engines, perform diagnosis of primary ignition circuit components using individual component diagnostic procedures.
Always turn the key OFF and isolate both ends of a circuit whenever testing for short or continuity.
Always disconnect solenoids and switches from the harness before measuring for continuity, resistance or energizing by way of a 12 volt source.
Before performing any component testing, check for and if necessary repair the following: