Dodge Colt/Challenger/Conquest/Vista 1971-1989 Repair Guide

Relieving Fuel System Pressure

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CAUTION
Before servicing the fuel pump, fuel lines, fuel filter, throttle body, or fuel injector, release the fuel system pressure.

  1. Loosen the fuel filler cap to release any built-up fuel tank pressure.
  2.  
  3. Detach the injector wiring harness connector at the edge of the throttle body.
  4.  
  5. Connect a jumper wire between terminal No. 1 of the injector harness and a good engine ground.
  6.  
  7. Connect a second jumper wire between terminal No. 2 of the injector harness and touch the battery positive post for no longer than 5 seconds -this will release the fuel system pressure.
  8.  
  9. Remove the jumper wires.
  10.  
  11. Continue with the fuel system service.
  12.  

COMPONENT TESTING



Air Flow Sensor


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Fig. Fig. 1 The air flow sensor is located inside the air cleaner housing

The sensor is located inside the air cleaner housing. Disconnect the sensor wires, remove the air cleaner cover and unclip and remove the sensor. Check the resistance between terminal 1 and 4 in the sensor (the two adjacent top terminals). Resistance should be 2.5k omega at 68°F (20°C). Service as necessary, and install the sensor.

Injectors
  1. Set the ignition switch to OFF.
  2.  
  3. Disconnect the high tension lead from the ignition coil.
  4.  
  5. Remove the air intake pipe from the throttle body.
  6.  
  7. Visually inspect the injectors for cleanliness.
  8.  
  9. Have an assistant turn the key to START while you watch the injectors. A good squirt from each injector should be observed.
  10.  
  11. Have your assistant turn the key to OFF. No leakage should occur.
  12.  
  13. Reconnect the coil wire. If the injectors do not perform properly, proceed to the injector coil test below.
  14.  

Injector Coil
  1. Turn the ignition switch to OFF.
  2.  
  3. Disconnect the wires from the injectors.
  4.  
  5. Check across the injector coil leads with an ohmmeter. Resistance should be 2.0-3.0 omega . If not, replace the injector.
  6.  
  7. Reconnect the wires.
  8.  

Idle Switch


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Fig. Fig. 2 Check for continuity between terminal 2 of the idle switch connector and the throttle body

  1. Turn the ignition switch OFF.
  2.  
  3. Disconnect the ISC servo.
  4.  
  5. Check for continuity between pole 2 (see accompanying illustration) of the connector, and the throttle body. With the throttle body at idle, there should be continuity; with the throttle wide open, there should be no continuity. With the throttle open, the lever should break contact with the idle switch.
  6.  
  7. If the continuity test is defective, replace the ISC servo.
  8.  
  9. Reconnect the wiring.
  10.  

ISC Servo


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Fig. Fig. 3 Using an ohmmeter, test for continuity between the throttle body and terminal 3 of the ISC servo

  1. Without disconnecting the ISC servo, connect a voltmeter between terminal 3 in the illustration and the throttle body.
  2.  
  3. Turn the ignition switch from OFF to ON, and keep it at ON for at least 15 seconds. The voltmeter should indicate 11-13v, then momentarily drop to 1v or less, and return to 6-13v. This indicates normal operation.
  4.  
  5. Turn the switch OFF and remove the voltmeter.
  6.  

ISC Servo Motor
  1. With the ignition switch OFF, disconnect the ISC servo.
  2.  
  3. Check the motor coil with an ohmmeter for continuity between terminals 1 and 4. Resistance should be 7.0-10.0 omega . If not, replace the servo assembly.
  4.  
  5. Make sure there is no continuity between either terminal 1 or 4 and the throttle body.
  6.  
  7. If there is continuity, there is a short in the coil and the servo must be replaced.
  8.  

Throttle Position Sensor


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Fig. Fig. 4 Check the resistance across terminals 1 and 3 of the connector on the throttle position sensor

  1. With the ignition switch OFF, disconnect the TPS connector.
  2.  
  3. Check resistance across terminals 1 and 3 (top and bottom left) of the connector. Resistance should be 4.0-6.0k omega .
  4.  
  5. Using a circuit test, cross connect terminals 1 and 3 or 2 and 3. Operate the throttle valve slowly from idle to wide open. The resistance should change smoothly.
  6.  
  7. Remove the testers and connect the wires.
  8.  

 
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