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Ignition System - Hall Effect Audi 4000 S Quattro

Ignition System 5 illustrations ~1585 words

DESCRIPTION

Note. Ignition system on Audi Coupe GT, 4000S Quattro, and 5000S is controlled by the CIS-E electronic control system. See BOSCH CIS-E ELECTRONIC CONTROL SYSTEM in COMPUTER CONTROLS section.

The typical Bosch Hall Effect electronic ignition system consists of an ignition coil, Hall Effect sending unit (in distributor), Hall control unit, distributor, spark plug wires, and spark plugs.

During engine operation, ignition timing is controlled by the electronic ignition control unit after receiving signals from the knock sensor, idle switch, full throttle switch, and engine vacuum (vacuum hose is connected directly into ignition control unit).

OPERATION

The Hall Effect sending unit is mounted inside the distributor on a switch plate. A trigger wheel attached to the distributor shaft under the rotor, passes in and out of the air gap of the Hall Effect sending unit. There is 1 trigger wheel shutter for each cylinder of the engine. Shutter width determines dwell, which is not adjustable.

At speeds greater than 940 RPM the Hall Effect sending unit signals the ignition control unit to make and break current flow in the primary circuit of the ignition coil.

As the ignition control unit breaks the primary circuit through the coil, secondary voltage is released through the high tension wiring, distributor cap and rotor to the spark plugs.

The idle stabilizer is mounted on the same bracket as the Hall control unit and is wired between the distributor and the Hall control unit. It senses engine speed earlier, causing ignition timing to advance.

Advancing ignition timing causes idle speed to increase, and the Hall generator to resume its normal operation.

PRE-TEST PROCEDURES

  1. Ensure the battery is fully charged and in good condition before making tests. Check all wiring harnesses, ignition switch, ignition coil connections, spark plug cables and connectors.
  2. DO NOT connect any condenser to terminal 1 of ignition coil. Connect and disconnect test instruments only when ignition is off. DO NOT touch or remove high tension wires when engine is running or cranking.
  3. Disconnect ignition wires only when ignition is off. DO NOT crank engine unless high tension wire is removed from distributor cap and grounded with a jumper wire.
  4. When installing suppressors, use only 1000 ohms for high tension wires and 1000-5000 ohms for spark plug connectors. DO NOT wash engine when it is running. DO NOT use a battery charger for more than 1 minute nor exceed 16.5 charging voltage.

Audi 4000S Electronic Ignition System Wiring Diagram. Scheme 1

Scheme 1: Audi 4000S Electronic Ignition System Wiring Diagram
Scheme 1: Audi 4000S Electronic Ignition System Wiring Diagram

Knock Sensor Test

  1. Turn ignition on. Engine warning lamp (on instrument panel) should come on. Start engine and accelerate engine to 3000 RPM (1 time only). Engine warning lamp must go off. If lamp goes out, test is completed.
  2. If lamp does not go out, install a fuse in test terminals of fuel pump relay for a minimum of 3 seconds. (Scheme 2) Engine warning lamp must start blinking. If lamp stays on, go to «TIMING ADVANCE TEST»(/audi/4000-s-quattro/1985-1985/remont/ignition-system/#ignition-system-hall-effect__timing-advance-test).
  3. If lamp blinks in intervals of 2, the knock sensor circuit is defective. Check knock sensor tightness. If loose, tighten knock sensor to 10 ft. lbs. (14 Nm). Check for open circuit in knock sensor wiring. If wiring is okay, knock sensor or Hall control unit is defective.
  4. If lamp blinks in intervals of 3, check White vacuum hose to electronic ignition control unit for damage. Check for faulty throttle switches. See «IDLE & FULL THROTTLE SWITCH TEST»(/audi/4000-s-quattro/1985-1985/remont/ignition-system/#ignition-system-hall-effect). If okay, pressure sensor in unit is faulty.

Audi 4000S Knock Sensor Test. Scheme 2

Scheme 2: Audi 4000S Knock Sensor Test
Scheme 2: Audi 4000S Knock Sensor Test

Timing Advance Test

Perform KNOCK SENSOR TEST . If knock sensor circuit is okay, check engine idle speed and timing. Adjust if necessary. With engine running, pull off White vacuum hose from intake manifold. Plug manifold connection. Increase engine speed to 3000 RPM. Check that timing is 20-24° BTDC. If timing is incorrect, Hall control unit is defective.

HALL CONTROL UNIT TEST

  1. Check ignition coil. See «IGNITION COIL RESISTANCE CHECK»(/audi/4000-s-quattro/1985-1985/remont/ignition-system/#ignition-system-hall-effect__ignition-coil-resistance-check) . Disconnect Hall control unit (in glove box) by pressing wire retaining clip. Set Digital Voltmeter (US 1119 ) on 20 volt scale. Connect voltmeter between terminal 2 and 4 at control unit connector.
  2. Turn ignition on. Voltmeter should indicate battery voltage. If reading is incorrect, find open circuit in wiring and repair as necessary. Connect voltmeter between terminal 4 and 6 at control unit connector.
  3. Crank engine and check signal from Hall Effect sending unit. Voltmeter should display some voltage. If voltage is displayed, check Hall Effect sending unit. See «HALL EFFECT SENDING UNIT TEST»(/audi/4000-s-quattro/1985-1985/remont/ignition-system/#ignition-system-hall-effect__hall-effect-sending-unit-test) .
  4. If no voltage is displayed, turn ignition off and reconnect Hall control unit. Disconnect connector to Hall Effect sending unit at distributor. Connect voltmeter between negative terminal 1 and positive terminal 15 on ignition coil.
  5. Turn ignition on. Initial meter reading should be 2 volts minimum, then voltage must drop to zero after 1-2 seconds. If reading is incorrect, replace Hall control unit.
  6. Check ignition coil and see if any sealing compound has leaked out. Replace coil if necessary. Briefly tap center wire from disconnected Hall sending unit connector to ground.
  7. Displayed voltage must increase a minimum of 2 volts for a short time. If reading is incorrect, replace Hall control unit. Turn ignition off. Reconnect Hall Effect sending unit.

HALL EFFECT SENDING UNIT TEST

Note. Perform this test only if spark is absent.

Scheme 3

Scheme 3: HALL EFFECT SENDING UNIT TEST
Scheme 3: HALL EFFECT SENDING UNIT TEST
  1. Disconnect Hall control unit (in glove box) by pressing wire retaining clip. Set Digital Voltmeter (US 1119 ) on 20 volt scale. Connect voltmeter between terminal 4 and 6 at control unit connector. (Scheme 3)
  2. Crank engine and check signal from Hall Effect sending unit. Voltmeter should display some voltage. If voltage is displayed, Hall Effect sending unit is okay. Test is completed. (Scheme 3): Audi 4000S Hall Effect Sending Unit Test
  3. If no voltage is displayed, turn ignition off and reconnect Hall control unit. Disconnect connector to Hall Effect sending unit at distributor. Connect voltmeter to outer connector terminals and check voltage supply (from Hall control unit) to sending unit.
  4. Voltmeter should indicate battery voltage. Slide rubber boot away from Hall sending unit connector. Connect voltmeter between battery positive terminal and center wire on connector.
  5. Crank engine and check signal from Hall Effect sending unit. Voltmeter should display an alternating voltage. If not, ignition distributor and/or Hall control unit is defective. Reposition boot.

Voltage Test

Connect Test Lead (VW 1501 ) between feed line to throttle switches and wire connector. (Scheme 4) Turn ignition on. Check voltage between ground and connector 2 on test lead. Voltmeter reading should be 12 volts. Turn ignition off. If reading is incorrect, check for open circuit in wiring and repair as necessary.

Idle Switch

  1. Turn ignition on. Check voltage between ground and connector 1 on test lead. (Scheme 4) Voltmeter reading should be 12 volts. Open throttle body; then slowly close it. While doing this, use a feeler gauge to measure point at which idle switch closes.
  2. Idle switch-to-idle stop gap should be 0.006-0.02" (0.15-0.5 mm). If gap is incorrect, move switch to adjust gap. If gap is correct, check full throttle switch.

Idle & Full Throttle Switch Tests Idle switch test shown, full throttle switch test is similar. Scheme 4

Scheme 4: Idle & Full Throttle Switch Tests Idle switch test shown, full throttle switch test is similar.
Scheme 4: Idle & Full Throttle Switch Tests Idle switch test shown, full throttle switch test is similar.

Full Throttle Switch

  1. Turn ignition on. With throttle body completely open, check voltage between ground and connector 3 on test lead. Voltmeter reading should be 12 volts.
  2. Using a screwdriver, push throttle body lever toward full throttle stop. While doing this, use a feeler gauge to measure point at which full throttle switch closes.
  3. Full throttle switch gap should be 0.03-0.05" (0.8-1.2 mm). If not, move switch to adjust gap. Ensure that throttle body lever roller contacts edge of full throttle switch lever.

IGNITION COIL RESISTANCE CHECK

  1. Turn ignition off and disconnect all wires from ignition coil. Using an ohmmeter, measure resistance between coil primary terminals 1 and 15. Ohmmeter reading must be 0.52-0.76 ohms.
  2. Measure resistance between coil tower and negative coil terminal 1. Ohmmeter reading must be 2400-3500 ohms. If readings are incorrect, replace ignition coil.

SPARK PLUG WIRES & ROTOR

  1. Check coil wire resistance. If radio suppression wires are used, reading should be 1200-2800 ohms. If not, reading should be zero ohms. Check resistance of spark plug wires.
  2. If radio suppression wires are used, reading should be 4600-7400 ohms. If not, reading should be 600-1400 ohms. Check spark plug connectors. If radio suppression connectors are used, reading should be 4000-6000 ohms.
  3. If not, reading should be 600-1400 ohms. Check rotor and spark plug wire distributor cap connectors. Resistance should be 600-1400 ohms. Ensure that rotor is marked "R1".

DISASSEMBLY

  1. Loosen ground strap and remove static shield from distributor cap. (Scheme 5) Remove cap, rotor, carbon brush and spring. Remove dust cover. Remove connector from distributor by depressing retaining clip.
  2. Remove retaining snap ring. Carefully pry off trigger wheel. Remove washers. Remove screws and lift out Hall sending unit and connecting socket. Remove base plate and vacuum unit. Remove pin and distributor drive pinion and shims.

Exploded View of Bosch Hall Effect Distributor. Scheme 5

Scheme 5: Exploded View of Bosch Hall Effect Distributor
Scheme 5: Exploded View of Bosch Hall Effect Distributor

REASSEMBLY

  1. To assemble, reverse disassembly procedure. On Audi, if a new Hall Effect sending unit (generator) is being installed, a special repair kit is available containing all necessary parts.
  2. Replace seals, and check components for cracks, corrosion and wear. Clean cap before installing. If trigger wheel was bent during removal, it must be replaced.