Chrysler Front Wheel Drive Cars 6-CYL 1988-1995 Repair Information

Distributor Pick-up

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The distributor pick-up is a Hall-effect sensor which combines the functions of a crankshaft position sensor and a camshaft position sensor. This sensor is only used by the 3.0L engines (except Premier and Monaco).

OPERATION

See Figures 1 and 2

The distributor pick-up provides two inputs to the PCM. From one input the PCM determines RPM (engine speed). From the other input it derives crankshaft position. The PCM regulates injector synchronization and adjusts ignition timing and engine speed based on these inputs.

The distributor pick-up contains two signal generators. The pick-up unit consists of 2 Light Emitting Diodes (LED), 2 photo diodes, and a separate timing disk. The timing disk contains two sets of slots. Each set of slots rotates between a LED and a photo diode. The inner set contains 6 large slots, one for each cylinder. The outer set contains several smaller slots.

The outer set of slots on the rotating disk represents 2° of crankshaft rotation. Up to 1200 engine RPM, the PCM uses the input from the outer set of slots to increase ignition timing accuracy.



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Fig. Fig. 1: Side view of the distributor pick-up assembly-3.0L engines, except Premier or Monaco

The outer set of slots contains a 10° flat spot. The flat spot tells the PCM that the next piston at TDC will be No. 6. The position of each piston is referenced by one of the six inner slots.

As each slot on the timing disk passes between the diodes, the beam from the LED is interrupted. This creates an alternating voltage in each photo diode which is converted into on-off pulses. The pulses are input to the PCM.



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Fig. Fig. 2: Top view of the optic unit and the slotted timing disk

During cranking, the PCM cannot determine crankshaft position until the 10° flat spot on the outer set of slots passes through the optical unit. Once the flat spot is detected, the PCM knows piston No. 6 will be the next piston at TDC.

Since the disk rotates at half crankshaft speed, it may take 3 engine revolutions during cranking for the PCM to determine the position of piston No. 6. For this reason the PCM will energize all six injectors at the same time until it senses the position of piston No. 6.

TESTING



See Figure 3

  1. Check for stored trouble codes, then proceed as follows:

    Fault code 11-proceed to the next step.
     
    Fault code 54-proceed to step 6 .
     

  2.  

Before proceeding, verify that a minimum of 12.4 volts is available from the battery for operation of cranking and ignition systems.

  1. Test the distributor pick-up signal reference circuit as follows:
    1. Turn the ignition switch to the OFF position.
    2.  
    3. Unplug the distributor pick-up connector.
    4.  
    5. Remove the coil wire from the distributor cap and have an assistant hold it 1 / 4 in. (6mm) from a good engine ground.
    6.  
    7. Turn the ignition switch to the ON position.
    8.  
    9. Connect a jumper wire to the gray (GY) wire terminal and touch the other end of the jumper wire to the black/light blue (BK/LB) wire terminal on the distributor harness connector several times. While performing this, observe the coil wire.

      If there is spark from the coil wire, proceed to the next step
       
      If there is no spark from the coil wire, the problem is in the engine controller or wiring.
       

    10.  

  2.  



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Fig. Fig. 3: Distributor harness connector terminal identification-3.0L engines, except Premier and Monaco

  1. Check the power supply to the distributor reference pick-up as follows:
    1. Turn the ignition switch to the ON position.
    2.  
    3. Connect a voltmeter between the orange wire in the harness connector and a known good ground.

      If the reading on the voltmeter is 8-9.5 volts, proceed to the next step.
       
      If the reading is anything but 8-9.5 volts, check for problems in the circuit between the reference connector and the engine controller.
       

    4.  

  2.  
  3. Check the mechanical operation of the distributor as follows:
    1. Turn the ignition switch to the OFF position.
    2.  
    3. Remove the distributor cap from the distributor housing.
    4.  
    5. Crank the engine while observing the ignition rotor.

      If the distributor rotor revolves while the engine is being cranked over, replace the distributor pick-up coil assembly with a new one.
       
      If the distributor rotor did not rotate, inspect the engine for a mechanical fault and repair as necessary.
       

    6.  

  4.  
  5. If fault code 54 (No distributor sync pick-up signal) is being received, or was received before performing this test, proceed as follows:
    1. Turn the ignition switch to the OFF position.
    2.  
    3. Unplug the distributor pick-up connector.
    4.  
    5. Connect a voltmeter to the tan/yellow (TN/YL) wire of the harness connector.
    6.  
    7. Turn the ignition switch to the ON position.

      If the reading on the voltmeter is at 4 volts, replace the distributor pick-up coil assembly.
       
      If the reading is 0 volts, check for an open in the wiring harness between the reference connector and the engine controller.
       

    8.  

  6.  

REMOVAL & INSTALLATION



See Figures 4 through 19

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the distributor from the engine as described in Engine Electrical .
  4.  
  5. Remove the distributor cap retaining screws.
  6.  
  7. Remove the distributor cap and inspect for flashover, cracked carbon button, cracked cap, or burned terminals. If any of these conditions exist, replace the cap with a new one.
  8.  
  9. Remove the rotor screw. Inspect the rotor for cracks or burned electrodes. If any of these conditions exist, replace the rotor.
  10.  
  11. Remove the protective cover from the distributor housing.
  12.  
  13. Remove the lead wire clamp screw and remove the lead wire.
  14.  
  15. Remove the disk assembly screw.
  16.  

When removing the disk and spacers, note the placement of the spacers for reassembly.

  1. Remove the disk spacers and disk. Disk and spacers are keyed. Check the disk for warpage, cracks or damaged slots. If any of these conditions are found, replace the disk with a new one.
  2.  
  3. Remove the bushing and photo optic sensing unit fasteners. Remove the unit from the distributor housing.
  4.  

To install:
  1. Install the photo optic sensing unit and bushing back into the distributor. Tighten the screws until snug.
  2.  
  3. Install the disk spacers and disk (new one if necessary).
  4.  
  5. Install the disk assembly retaining screw until snug.
  6.  
  7. Install the lead wire and secure in place with the wire clamp. Make certain that the lead wire plug is completely seated into the bottom of the optic unit.
  8.  
  9. Install the protective cover into the distributor housing.
  10.  
  11. Install the rotor so that the rotor screw hole and the screw hole in the rotor shaft are aligned. Tighten the rotor locking screw until snug.
  12.  
  13. Install the distributor cap and secure it in place with the screws.
  14.  
  15. Install the distributor into the vehicle as described in Engine Electrical .
  16.  
  17. Connect the negative battery cable.
  18.  



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Fig. Fig. 4: Remove the rotor retaining screw to lift the rotor off of the distributor shaft



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Fig. Fig. 5: Remove the protective cover to gain access to the pick-up



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Fig. Fig. 6: Remove the lead wire clamp and wire assembly from the distributor



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Fig. Fig. 7: Loosen the center distributor shaft screw, then lift the distributor shaft extension off of the photo disc



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Fig. Fig. 8: The disc can be removed from the distributor by only loosening the screws, then sliding the disc out of the unit



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Fig. Fig. 9: Disk and spacers removed from the distributor-3.0L engines, except Premier and Monaco



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Fig. Fig. 10: Photo optic sensing unit assembly (pick-up) and bushing-3.0L engines, except Premier and Monaco



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Fig. Fig. 11: After removing the distributor cap, loosen the retaining screw, then pull the rotor off of the distributor



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Fig. Fig. 12: Loosen and remove the pick-up sensor cover retaining screws, then ...



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Fig. Fig. 13: ... remove the cover from the distributor, thereby exposing the pick-up mechanism



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Fig. Fig. 14: Remove the center shaft mounting screw and ...



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Fig. Fig. 15: ... lift the center shaft off of the distributor



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Fig. Fig. 16: Loosen the 2 upper pick-up module mounting screws, then...



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Fig. Fig. 17: ... while holding the module up off of the disk, extract the optical disk from the distributor



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Fig. Fig. 18: Distributor schematic showing the pick-up components-3.0L engines, except Premier and Monaco



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Fig. Fig. 19: Note the indexing flat in the center mounting hole and the small window flat (by the thumb)

 
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