Volkswagen Front Wheel Drive 1974-1989 Repair Guide

Diagnosis & Testing

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These components must be tested using the order presented. Keep in mind that not all systems will use all of the components listed.

IGNITION COIL



See Figure 1

Quantum, Fox and 1979-84 Rabbit, Scirocco and Jetta
  1. Label and disconnect all wires from the ignition coil.
  2.  
  3. With an ohmmeter, measure between terminals 15 and 1 (primary resistance). Check that the ohmmeter reading is between 0.52-0.76 ohms. If not, replace the coil.
  4.  
  5. Measure the resistance between terminals 1 and 4 (secondary resistance). The reading should be between 2,400-3,500 ohms. If not, replace the coil.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: Ignition coil terminal identification

1985-89 Scirocco, Cabriolet, Golf and Jetta
  1. Label and disconnect all wires from the ignition coil.
  2.  
  3. With an ohmmeter, measure between terminals 15 and 1 (primary resistance). Check that the ohmmeter reads as follows. If not, replace the coil.

    On CIS 8-valve engines-0.52-0.76 ohms
     
    On 16-valve engines-0.5-0.8 ohms (yellow and gray labels)
     
    On Digifant II 8-valve engines-0.6-0.8 ohms (gray label) 0.52-0.76 ohms (green label)
     

  4.  
  5. Measure the resistance between terminals 1 and 4 on CIS 8-valve engines with knock sensor systems. Measure between 15 and 4 on all others (secondary resistance). The reading should be as follows. If not, replace the coil.

    On CIS 8-valve engines-2,400-3,500 ohms
     
    On 16-valve engines-6,500-8,500 ohms (yellow label) 6,900-8,500 ohms (gray label)
     
    On Digifant II 8-valve engines-6,900-8,500 (gray label) 2,400-3,500 ohms (green label)
     

  6.  

HALL CONTROL UNIT



Except Digifant II and Knock Sensor Systems

See Figures 2 and 3

  1. Unplug the Hall control unit harness connector (at the control unit).
  2.  
  3. Using a digital multimeter switched to the 20V range, connect the meter positive lead to terminal 4 and the negative lead to terminal 2 of the harness connector.
  4.  



Click image to see an enlarged view

Fig. Fig. 2: Connect the meter positive lead to terminal 4 and the negative lead to terminal 2 of the harness connector

  1. Turn the ignition key to the ON position. The meter must read approximately battery voltage. If not, check for an open circuit in the wiring.
  2.  
  3. Turn the ignition to the OFF position. Reconnect the control unit harness.
  4.  
  5. Unplug the harness connector from the Hall sender at the distributor. Using a digital multimeter switched to the 20V range, connect the meter positive lead to terminal 15 and the negative lead to terminal 1 of the ignition coil.
  6.  
  7. Turn the ignition switch to the ON position. The meter must read a 2 volt minimum, then drop to 0 volts after 1-2 seconds. If not, replace the Hall control unit and the ignition coil.
  8.  
  9. Using a jumper wire, briefly touch the center wire of the harness connector to ground. Displayed voltage must rise briefly to 5-6 volts on Quantum and 1979-84 Rabbit, Scirocco and Jetta. Voltage must rise to a 2 volt minimum on other models. If not, determine if there is a open in the center wire.
  10.  
  11. Turn the ignition switch to the OFF position. Connect the multimeter to the outer terminals of the distributor (Hall sender) harness connector.
  12.  



Click image to see an enlarged view

Fig. Fig. 3: Connect the multimeter to the outer terminals of the distributor (Hall sender) harness connector

  1. Turn the ignition switch ON , there must be a minimum of 5 volts.
  2.  

Knock Sensor Systems

See Figures 4 and 5

  1. Unplug the Hall control unit harness connector (at the control unit).
  2.  
  3. Using a digital multimeter switched to the 20V range, connect the meter positive lead to terminal 4 and the negative lead to terminal 2 of the harness connector.
  4.  



Click image to see an enlarged view

Fig. Fig. 4: Terminal identification and multimeter hook-up on the Hall control unit harness connector

  1. Turn the ignition key to the ON position. The meter must read approximately battery voltage. If not, check for an open circuit in the wiring.
  2.  
  3. Turn the ignition to the OFF position. Check the wire from terminal 1 on the harness connector to terminal 1 of the ignition coil for continuity using an ohmmeter. Reconnect the control unit harness.
  4.  
  5. Unplug the harness connector from the knock sensor control unit. Using a digital multimeter switched to the 20V range, connect the meter positive lead to terminal 15 and the negative lead to terminal 1 of the ignition coil.
  6.  
  7. Turn the ignition switch to the ON position. The meter must read a 2 volt minimum, then drop to 0 volts after 1-2 seconds. If not, replace the Hall control unit and inspect the ignition coil for fluid leakage. Replace, if leaking.
  8.  
  9. Using a jumper wire, briefly touch terminal 12 of the harness connector to ground. Displayed voltage must rise briefly to a 2 volt minimum. If not, replace the Hall control unit.
  10.  



Click image to see an enlarged view

Fig. Fig. 5: Knock sensor control unit terminal identification

Digifant II

See Figures 6 and 7

Before testing, visually inspect all components of the system. Replace any noticeably damaged parts. Be sure to check the ignition coil and replace if it is leaking fluid.

  1. Unplug the Hall control unit harness connector (at the control unit).
  2.  
  3. Using a digital multimeter switched to the 20V range, connect the meter positive lead to terminal 4 and the negative lead to terminal 2 of the harness connector.
  4.  



Click image to see an enlarged view

Fig. Fig. 6: Connect the meter positive lead to terminal 4 and the negative lead to terminal 2 of the control unit harness connector

  1. Turn the ignition key to the ON position. The meter must read approximately battery voltage. If not, check for an open circuit in the wiring.
  2.  
  3. Turn the ignition to the OFF position. Reconnect the control unit harness.
  4.  
  5. Unplug the harness connector from the Digifant control unit. Using a digital multimeter switched to the 20V range, connect the meter positive lead to terminal 15 and the negative lead to terminal 1 of the ignition coil. If necessary, unplug the wiring from ignition coil terminal 1, then reconnect it so that only the wire to the Hall control unit is engaged.
  6.  
  7. Turn the ignition switch to the ON position. The meter must read a 2 volt minimum, then drop to 0 volts after 1-2 seconds. If not, replace the Hall control unit.
  8.  
  9. Using a jumper wire, briefly touch terminal 25 of the Digifant control unit harness connector to ground. Displayed voltage must rise briefly to a 2 volt minimum.
  10.  



Click image to see an enlarged view

Fig. Fig. 7: Use a jumper wire to touch terminal 25 to ground

  1. Turn the ignition switch to the OFF position. Reconnect the control unit harness.
  2.  

HALL SENDER



CIS and CIS-E Fuel Systems
QUANTUM, FOX AND 1979-84 RABBIT, SCIROCCO AND JETTA

See Figure 8

  1. If equipped, unplug the idle stabilizer (ignition advance type) plugs, then connect them together.
  2.  
  3. Unplug the high tension coil wire, then ground it using a jumper wire.
  4.  
  5. Slide the rubber boot away from the back of the Hall control unit harness connector (leave the harness engaged).
  6.  
  7. Using a digital multimeter switched on the 20V scale, connect the positive lead to terminal 6 and the negative lead to terminal 3. Turn the ignition switch ON .
  8.  



Click image to see an enlarged view

Fig. Fig. 8: Connect the positive lead of the multimeter to terminal 6 and the negative lead to terminal 3. Note that the rubber boot is folded back to allow access to the terminals

  1. Turn the engine slowly by hand in the direction of engine rotation. When the engine is rotating, the shutter of the trigger wheel will pass thorough the air gap of the Hall generator.
    1. On the Quantum, and 1979-84 Rabbit, Scirocco and Jetta, when the shutter is outside the air gap voltage should read between 0-0.7 volts. When the shutter is between the air gap, voltage should read from 1.8 volts through battery voltage.
    2.  
    3. On Fox models, the display must alternate between 0 and 2 volts as the engine is being rotated.
    4.  

  2.  
  3. If not, replace the Hall sender.
  4.  

1985-89 GOLF, JETTA, SCIROCCO AND CABRIOLET

See Figure 9

  1. Unplug the harness from the Hall control unit.
  2.  
  3. Connect a LED test light to terminals 4 and 6 (on CIS) or 2 and 6 (on CIS-E) of the harness connector.
  4.  
  5. Operate the starter, the LED on the test light must flicker.
  6.  
  7. If not, replace the Hall sender.
  8.  



Click image to see an enlarged view

Fig. Fig. 9: Harness terminal identification-NOTE: you should always use a LED test light

Digifant II Fuel Systems
  1. Unplug the Hall sender harness connector at the distributor.
  2.  
  3. Using a digital multimeter switched to the 20V range, measure the voltage between the outer terminals of the harness connector.
  4.  
  5. Turn the ignition switch to the ON position. There must be a minimum of 10 volts displayed. If not, check for an open circuit in the wiring and low battery voltage. If these are OK, replace the Digifant control unit.
  6.  
  7. Turn the ignition switch OFF . Unplug the main fuel injector harness connector. Push up the rubber boot (covering the Hall sender connector) to expose the terminals, then reconnect it to the distributor.
  8.  
  9. Connect a LED test light between the center terminal and either of the outer terminals. When the starter is operated, the LED should flicker, indicating a signal voltage is being generated by the Hall sender. If not, replace the distributor.
  10.  
  11. Connect a LED test light between terminals 1 and 15 of the ignition coil. If necessary, unplug the wiring from ignition coil terminal 1, then reconnect it so that only the wire to the Hall control unit is engaged.
  12.  
  13. When the starter is operated, the LED must flicker. If not, replace the control unit.
  14.  

KNOCK SENSOR SYSTEMS



Control Unit

See Figures 10, 11 and 12

  1. Unplug the harness from the Hall control unit. Turn the ignition switch to the ON position.
  2.  
  3. Using a digital multimeter switched on the 20V range, measure the voltage between terminals 3 and 5 of the harness. The meter display should read approximately battery voltage.
  4.  
  5. Measure between terminals 6 and 3. Once again, the display should read approximately battery voltage.
  6.  
  7. Open the throttle valve. The reading must drop to 0 volts. If not, check the throttle valve switch 1 (idle switch) for proper operation.
  8.  



Click image to see an enlarged view

Fig. Fig. 10: Knock sensor control unit terminal identification

  1. Measure voltage between terminals 8 and 3, while slowly opening the throttle valve. The reading should show approximately battery voltage. If not, check throttle valve switch 2 (full throttle switch).
  2.  
  3. Turn the ignition switch OFF . Measure resistance between terminals 13 and 14 with an ohmmeter. If equipped with knock sensor type 1, the meter display should read approximately 300k ohms. On type 2 sensors, the meter should display infinite resistance.
  4.  



Click image to see an enlarged view

Fig. Fig. 11: Type 1 knock sensor. Type 2 sensors have a connection on the side

Type 1 sensors have a cable connection which is off center (see illustration). On type 2 sensors, the connection is from the side.

  1. Reconnect the knock sensor control unit harness. Unplug the harness connector from the Hall sender at the distributor.
  2.  
  3. Connect the multimeter to the outer terminals of the connector. Turn the ignition switch ON . The meter display should read a minimum of 5 volts. Turn the ignition OFF .
  4.  



Click image to see an enlarged view

Fig. Fig. 12: Connect a multimeter to the outer terminals of the Hall sender (distributor) connector. A jumper wire can be used to touch the center terminal to ground

  1. Connect the multimeter between terminals 1 and 15 of the ignition coil. Turn the ignition switch ON . Use a jumper wire to touch the center terminal of the connector to ground. Voltage value must rise briefly to a minimum of 2 volts. If not, replace the Hall control unit.
  2.  

Control Unit Vacuum Sensor and Hose

See Figure 13

  1. Engage a LED test light to test connector 1 (a single connector with a blue/brown lead) and the positive battery cable. The LED must light up.
  2.  



Click image to see an enlarged view

Fig. Fig. 13: Engage a LED test light to test connector 1 (a single connector with a blue/brown lead) and the positive battery cable

  1. Start the engine. The LED should go out, however a very slight glow is acceptable.
  2.  
  3. Increase the engine speed to over 3,000 rpm one time.
  4.  
  5. Connect a jumper wire from test connector 1 and hold it to ground for at least 3 seconds.
  6.  
  7. After that, the LED must begin blinking. Observe the following patterns:

    Blinking twice in intervals means there is a fault in the knock sensor (this can be due to a break in the wiring, the knock sensor bolt not torqued to specification or a defective knock sensor) or the knock sensor control unit may be defective.
     
    Blinking three times in intervals means a break in the vacuum hose to the knock sensor control unit or that the vacuum sensor in the knock sensor control unit is defective.
     

  8.  

IDLE STABILIZER CONTROL UNIT



See Figure 14

This applies only to ignition advance type idle stabilizers.

If the engine is difficult to start, does not start or misfires/cuts out, test the idle stabilizer as follows.

  1. Disconnect the plugs from the stabilizer, then connect them together. Start the engine. If the troubles are now eliminated, check the contact pins and sockets of both idle stabilizer connectors for damage. If these are OK, the stabilizer control unit is probably defective.
  2.  



Click image to see an enlarged view

Fig. Fig. 14: Disengage the plugs from the stabilizer, then connect them together

  1. Reconnect the plugs to the idle stabilizer. Run the engine until it reaches normal operating temperature. With all accessories off, make sure engine speed is below 1,000 rpm. Check the ignition timing and make a note of the reading.
  2.  
  3. Turn all electrical accessories ON except the air conditioning. Check the timing and compare it to the first reading. It must be advanced, if not, replace the stabilizer control unit.
  4.  

On 1979-82 models, the idle speed must drop below 940 rpm for the idle stabilizer to advance timing. On 1983 and later models, the idle speed must drop below 840 rpm. If the idle speed is not brought down by the increased electrical load to below these specifications, the stabilizer will not advance the timing.

 
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