Chrysler Full-Size Vans 1967-1988 Repair Guide

Diagnosis and Testing

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See Figures 1, 2, 3, 4, 5, 6, 7, 8 and 9

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Fig. Fig. 1: Special jumper wire used to ground the coil negative terminal on 1972-87 systems



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Fig. Fig. 2: Test for battery voltage at the coil positive terminal. If no voltage is found, check the wires and ballast resistor



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Fig. Fig. 3: Test for battery voltage at the coil negative terminal-should be within one volt of battery voltage



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Fig. Fig. 4: Testing for voltage at cavity no. 2 of the ECU connector-should be within one volt of battery voltage



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Fig. Fig. 5: Checking for continuity between cavity no. 2 and the ignition coil negative terminal



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Fig. Fig. 6: Checking for continuity between cavity no. 1 and the ignition switch



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Fig. Fig. 7: Checking resistance between cavity nos. 4 and 5



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Fig. Fig. 8: Checking resistance of the pick-up coils



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Fig. Fig. 9: Testing for a short at each pick-up coil terminal

To properly test the Electronic Ignition System, special testers should be used. But, in the event they are not available, the system may be tested using a voltmeter with a 20,000 ohm/volt rating and an ohmmeter which uses a 9 volt battery for its operation. Both meters should be in calibration.

PRELIMINARY TESTS



  1. Visually inspect all secondary cables at the coil, distributor and spark plugs for cracks and tightness.
  2.  
  3. Check the primary wire at the coil and ballast resistor for tightness.
  4.  


CAUTION
Whenever removing or installing the wiring harness connector to the control unit, the ignition switch must be in the OFF position.

  1. With a voltmeter, measure the voltage at the battery and to ascertain that enough current is available to operate the cranking and ignition systems.
  2.  
  3. Remove the coil secondary wire from the distributor cap.
  4.  
  5. With the key ON, use a jumper wire and momentarily touch the negative terminal of the coil to ground while holding the coil secondary wire approximately 1 / 4 " from a good engine ground. A spark should be observed.
  6.  
  7. If no spark is obtained, turn the ignition key to the OFF position and disconnect the four wire harness going to the ECU control unit.
  8.  
  9. With the ignition key in the ON position, again use the jumper wire and ground the negative terminal of the coil to ground while holding the coil secondary wire approximately 1 / 4 " from a good engine ground. If a spark is observed, replace the ECU.
  10.  
  11. If no spark is observed, measure the voltage at the coil positive terminal. The voltage should be within one volt of battery voltage.
  12.  
  13. If battery voltage is not present, check wiring between battery positive terminal and the coil. Replace the starter relay if the wiring is correct.
  14.  
  15. If the current is not continuous between the battery and the coil positive terminal, replace the ignition resistor and repeat the test.
  16.  
  17. Check the battery voltage at the coil negative terminal. It should be within one volt of battery voltage.
  18.  
  19. If battery voltage is present at the negative coil terminal, but no spark is obtained when shorting the terminal with a jumper wire, replace the ignition coil.
  20.  
  21. If spark is obtained, but the engine will not start, turn the ignition switch to the OFF position and pull the ECU harness connector off, turn the ignition switch to the ON position and check for battery voltage at cavity No. 2 of the ECU harness connector. The voltage should be within one volt of battery voltage.
  22.  
  23. If no battery voltage is present, turn the ignition switch to the OFF position and check for continuity between cavity No. 2 and the coil negative terminal. If no continity is obtained, find the wiring fault, repair it and retest.
  24.  
  25. Check for continity between cavity No. 1 of the ECU connector and the ignition switch. If none exists, find the fault, repair it and retest.
  26.  
  27. If voltage is obtained at cavity No. 2 of the ECU connector, Turn the ignition switch to the OFF position and with an ohmmeter, check the resistance between cavities No. 4 and No. 5 of the ECU connector. The reading should range between 150 and 900 ohms.
  28.  
  29. If the resistance is not between 150 and 900 ohms, Disconnect the distributor pick-up leads. Measure the resistance at the pick-up leads. The resistance should be between 150 and 900 ohms. If the resistance is not within the accepted range, the pick-up coils are bad and must be replaced.
  30.  
  31. If the resistance at the pick-up leads is within specifications, thei would indicate the wiring between cavities No. 4 and No. 5 are open or shorted, or the dual pick-up start/run relay is defective. Repair and retest as required.
  32.  
  33. Check pin No. 5 of the ECU for ground. If no ground is obtained, check the ECU for poor or dirty connections and tight mounting screws.
  34.  
  35. Reinstall all connections and check for spark. If no spark occurs, replace the ECU.
  36.  

DUAL PICK-UP START/RUN RELAY TEST



  1. Remove the two way connector from pins No. 4 and No. 5 of the dual pick-up start/run relay.
  2.  
  3. Using an ohmmeter, touch pins No. 4 and No. 5. The meter should read 20-30 ohms. If not, replace the relay.
  4.  

CENTRIFUGAL ADVANCE



Test
  1. With a timing light connected, operate the engine at idle and remove the vacuum hose from the vacuum controller.
  2.  
  3. Slowly accelerate the engine to check for advance.
  4.  
  5. Excessive advance indicates a damaged governor spring (a broken spring will result in abrupt advance).
  6.  
  7. Insufficient advance is usually caused by a broken governor weight or a malfunction in cam operation. Correct as needed.
  8.  

VACUUM ADVANCE



Test
  1. Connect a timing light and adjust the engine speed to 2500 rpm.
  2.  
  3. Check for advance by disconnecting and then reconnecting the vacuum hose at the distributor and watching the advance or retard at the crankshaft indicator.
  4.  
  5. For a more accurate determination of whether the vacuum advance mechanism is operating properly, remove the vacuum hose from the distributor and connect a hand vacuum pump.
  6.  
  7. Run the engine at idle and slowly apply vacuum pressure to check for advance.
  8.  
  9. If excessive advance is noted, look for a deteriorated vacuum controller spring.
  10.  
  11. If insufficient advance or no advance is noted, this could be caused by linkages problems or a ruptured vacuum diaphragm. Correct as necessary.
  12.  

 
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