Chrysler Full-Size Trucks 1989-1996 Repair Guide

Diagnosis and Testing

Print

This group of procedures are basic tests of the secondary circuit. For information on the various sensors that supply data to the PCM, please refer to the index at the beginning of this section for assistance.

CHECKING FOR SPARK



See Figures 1, 2 and 3

The coil design was changed in 1993, but its function is the same. Therefore the test for all covered models is the same.

WARNING

Do not attempt to pull the wire from the distributor cap of the 2.5L engine. The cap must be removed and the wire released from inside the cap.

  1. Remove the coil wire from the distributor cap with an insulated spark plug puller tool. Using the insulated tool, hold the wire end cautiously about 1 / 2 in. (12mm) away from an engine ground. Use a remote starter switch or have an assistant crank the engine while checking for spark.
  2.  
  3. If a good spark (steady arcing of current) is not present, inspect the secondary coil wire.
  4.  
  5. If a good spark is seen, connect the wire to the distributor cap.
  6.  
  7. Remove the wire from one spark plug by grasping the rubber boot and twisting slightly as you pull, or use spark plug pliers.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Use a spark plug boot puller tool to reduce the chances of stressing the crimp at the wire and connector

  1. Using insulated pliers, hold the wire about 1 / 2 in. (12mm) away from a good engine ground and test for spark as you did previously. Be careful of the spark that should occur.
  2.  

The ignition coil wire should deliver a stronger, brighter spark than the spark plug wires. A somewhat lesser, duller spark at the spark plugs is a normal condition.

Click image to see an enlarged view

Fig. Fig. 2: Check the distributor cap for these conditions-replace if any are present



Click image to see an enlarged view

Fig. Fig. 3: Inspect the rotor for any of the damage shown and replace if damage is found

  1. If a good spark occurs, you are safe in assuming the ignition secondary system is operating correctly. If the engine does not start, proceed to the "Failure-To-Start'' test.
  2.  
  3. If no spark was found, inspect the distributor cap, rotor and wires.
  4.  

FAILURE-TO-START TEST



See Figures 4, 5 and 6

The "Checking For Spark'' test should be performed prior to this test.

This is a basic test of the ignition system that systematically examines the battery, the coil, the engine controller, and its wiring harness and connections; the most likely culprits in a no-start condition at this stage.



Click image to see an enlarged view

Fig. Fig. 4: Fabricate this special jumper with a 0.33 MF capacitor in-line to test the ignition coil

  1. Unplug the ignition coil harness connector at the coil.
  2.  
  3. Connect a set of small jumper wires (18 gauge or smaller) between the disconnected harness terminals and the ignition coil terminals.
  4.  



Click image to see an enlarged view

Fig. Fig. 5: Terminal locations on the engine controller 14-way connector-1989 models



Click image to see an enlarged view

Fig. Fig. 6: Engine controller 60-way connector-relevant terminals for testing are shown numbered

  1. Attach one lead of a a voltmeter to the positive (12V) jumper wire. Attach the negative side of the voltmeter to a good ground. Measure the voltage at the battery and confirm that enough current is available to operate the starting and ignition systems.
  2.  
  3. Crank the engine for five seconds while monitoring the voltage at the coil positive terminal:
    1. If the voltage remains at zero, diagnosis of the fuel system should be performed. Also check the engine controller and auto shutdown relay.
    2.  
    3. If voltage is at or near battery voltage and then drops to zero after one or two seconds of engine cranking, check the engine control module circuit.
    4.  

  4.  

WARNING

The ignition must be turned OFF prior to unplugging the engine controller connector. If it is not, electrical surging could occur causing damage to the unit or other electrical components in the vehicle.

  1. If the voltage remains at or near battery voltage during the entire five seconds, turn the ignition key OFF . Remove the 14-way connector on 1989 models, or the 60-way connector on 1990-96 models at the engine controller. Check the 14-way or 60-way connector for any spread terminals.
  2.  

  1. Remove the test lead from the coil positive terminal. Connect an 18 gauge jumper wire between the battery positive terminal and the coil positive terminal.
  2.  
  3. Make a special jumper cable (see illustration). Using the jumper MOMENTARILY ground terminal 12 on the 14-way connector (1989), or terminal 19 (see illustration) of the 1990-96 60-way connector. A spark should be generated at the coil wire when the ground is removed.
    1. If a spark is generated, replace the engine controller computer.
    2.  
    3. If no spark is seen, use the special jumper to ground the coil negative terminal directly. If spark is produced, repair the wiring harness for an open circuit condition. If spark is not produced, replace the ignition coil.
    4.  

  4.  

 
label.common.footer.alt.autozoneLogo