All Except CIS-E Motronic and Digifant I

Testing Hall Sender and Ignition Control Unit (all except CIS-E Motronic and Digifant I)
The Hall sender and ignition control unit only need to be tested it there is no spark at the spark plugs when tested. For these tests, the spark plug wires and ignition coil should be in good condition as described in 3.3 Testing Coil and Spark plug Wires. The ignition control unit is located in the driver's side cowling, above and behind the firewall, beneath the drip tray. The Hall sender connector is on the side of the distributor.

These tests require the use of a high-impedance voltmeter or low-current LED test light. For more information, see 3.1 Basic Troubleshooting Principles. The sequence of the tests below is important. Follow the test sequence as it is presented in order to logically isolate the faulty component.

CAUTION: Always turn the ignition off before connecting or disconnecting ignition test equipment. Switch multimeter functions or measurement ranges only with the test probes disconnected.

If it becomes necessary to remove or replace the ignition control unit, carefully clean the mounting surface between the control unit and the heat sink before installing. Trapping dirt or other debris beneath the control unit may damage the internal circuitry when the mounting screws are tightened.

Voltage Supply and Ground to Ignition Control Unit
With the ignition OFF, remove the harness connector from the ignition control unit. Check for voltage between connector terminals 2 (-) and 4 (+) as shown in Fig. 3-4. There should be battery voltage when the ignition is turned ON. If there is no voltage, check for wiring faults. Check the continuity of the wire from terminal 2 to ground, and from terminal 4 of the connector to terminal 15 of the coil. Repair wiring as necessary. For current flow diagrams, see WIRING DIAGRAMS.

Fig. 3-4:

Fig. 3-4. ignition control unit voltage supply being checked at connector terminals 2 and 4.

Voltage Supply and Ground to Hall Sender
The three ignition systems each get power to the Hall sender a different way. The basic TCI-h system powers the Hall sender through the ignition control unit. On the TCI-h system with knock sensor, the Hall sender receives power from the knock sensor control unit. On Digifant II system, the Digitant control unit powers the Hall sender.

With the ignition OFF and the ignition control unit connected, disconnect the harness connector from the Hall sender at the distributor. Check for voltage between the outer terminals of the connector, as shown in Fig. 3-5. There should be voltage when the ignition is switched ON.

If there is no voltage, use the current flow diagrams in WIRING DIAGRAMS to check the wiring between the Hall sender connector and the control unit, between the voltage source and the control unit, and between the control unit and ground. If all of these wires have continuity and there is still no voltage reaching the Hall sender, the control unit which provides power to the sender is faulty and should be replaced.

Fig. 3-5:

Fig. 3-5. Checking voltage supply at Hat sender connector. LED test light shown.

Hall Sender Switching Function
To check Hall sender function, check its ability to switch the primary circuit. Remove the coil wire from the center of the distributor and connect into ground with a jumper wire. With the Hall sender connected, carefully push back the rubber connector boot to expose the back of the wire connections. Connect an LED test light between the center terminal and the positive (+) battery terminal, as shown in Fig. 3-6. When the starter is actuated, the LED should flicker. If there is no reaction, the Hall sender is defective and should be replaced as described in Disassembling and Assembling Distributor.

Fig. 3-6:

Fig. 3-6. Hall sending unit switching tunction being tested with LED test light.

Ignition Control Unit Voltage to Coil
With the ignition off, connect the probes of a multimeter (20 DCV scale) to terminal 1 (-) and terminal 15 (+) of the ignition coil, as shown in Fig. 3-7. Do not disconnect the existing coil wiring. On models with the basic TCI-h system, disconnect the Hall sender connector at the distributor. On models with TCI-h and knock sensor, disconnect the harness connector from the knock sensor unit. On Digitant II models, disconnect the harness connector from the Digitant control unit.

Fig. 3-7:

Fig. 3-7. Voltage being measured at ignition coil terminals 1 (-) and 15 (+) (shown schematically).

When the ignition is switched ON, the meter should display a reading of at least 2 volts for approximately 1 to 2 seconds, and then drop to 0 volts. If not, either the ignition coil or the ignition control unit is defective. Check the coil as described in Ignition System Visual Inspection and in Testing Coil and Spark Plug Wires. If no coil faults are discovered, the ignition control unit is faulty and should be replaced.

Ignition Control Unit Response to Hall Sender Signal
With the voltmeter or multimeter connected as in the previous test, check the ignition control unit function by providing it with a simulated Hall sender signal. If the control unit does not respond as indicated, the ignition control unit is defective and should be replaced.

To test the basic TCI-h system, disconnect the Hall sender connector. Turn the ignition on and, using a jumper wire, briefly connect the center terminal of the Hall sender connector to ground, as shown in Fig. 3-8. The voltage should briefly increase to at least 2 volts.

Fig. 3-8:

Fig. 3-8. Center terminal of Hall sender connector being briefly connected to ground to test ignition control unit on TCI-h ignition system (shown schematically).

To test the TCI-h system with knock sensor, disconnect the knock sensor control unit harness connector. Turn the ignition ON and, using a jumper wire, briefly connect terminal 12 of the knock sensor control unit connector to ground as shown in Fig. 3-9. The voltage should briefly increase to at least 2 volts.

Fig. 3-9:

Fig. 3-9. Terminal 12 of the knock sensor control unit connector being briefly connected to ground to test ignition control unit on TCI-h ignition system with knock sensor. (Test shown schematically).

To test the Digitant II ignition system, disconnect the Digitant control unit harness connector. Turn the ignition on and, using jumper wire, briefly connect terminal 25 of the Digifant control unit connector to ground. Terminal locations are shown in Fig. 3-10. The voltage should rise briefly to at least 2 volts.

Fig. 3-10:

Fig. 3-1O. Terminal locations on Digifant control unit harness connector.