Mercury Villager 2000-2002

Diagnosis & Testing


Preliminary Checks

  1. Visually inspect the engine compartment to ensure that all vacuum lines and spark plug wires are properly routed and securely connected.
  3. Be certain that the battery is fully charged and that all accessories are OFF during the diagnosis.
  5. 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:

  1. With the ignition switch OFF , disconnect the coil harness connector from the coil.
  3. 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.)
    Do not let the test light probe contact any metal parts of the vehicle while it is connected to the positive battery terminal.

  5. Probe the green wire (pin 2) terminal in the ignition coil harness connector.
  7. 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

Click image to see an enlarged view

Fig. This spark tester looks just like a spark plug, attach the clip to ground and crank the engine to check for spark

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Fig. This spark tester has an adjustable air-gap for measuring spark strength and testing different voltage ignition systems

Click image to see an enlarged view

Fig. Attach the clip to ground and crank the engine to check for spark

Click image to see an enlarged view

Fig. This spark tester is the easiest to use just place it on a plug wire and the spark voltage is detected and the bulb on the top will flash with each pulse

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).

  1. Disconnect a spark plug wire at the spark plug end.
  3. Connect the plug wire to the spark tester and ground the tester to an appropriate location on the engine.
  5. Crank the engine and check for spark at the tester.
  7. If spark exists at the tester, the ignition system is functioning properly.
  9. 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.

Service Precautions

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.

Electronic modules are sensitive to static electrical charges. If the module is exposed to these charges, damage may result.

Before performing any component testing, check for and if necessary repair the following:

Damaged, fouled, improperly seated or gapped spark plug
Damaged or improperly engaged electrically connections, spark plug wires etc.
Discharged battery
Blown fuses