Ignition System - Bosch Ezk (v6) Volvo 760 I

DESCRIPTION

There are 3 types of the EZK systems. The systems are similar in components and operations. The Volvo 760 and 780 with B280F engines use an EZ115K type.

The EZK system consists of a breakerless Hall Effect distributor, an ignition Electronic Control Unit (ECU), a knock sensor, an LED knock indicator, an amplifier module, ignition coil and a potentiometer and microswitch mounted on the throttle housing.

OPERATION

Inputs from engine speed, engine load, detonation, throttle position and battery voltage are supplied to the microprocessor within the ignition module to determine spark advance. Only the engine load and engine speed input signal values are used to determine the timing signal entered in the memory of the micro-processor. The microprocessor, after analyzing the parameters of engine operation, will adjust timing accordingly.

The ECU output signals provide control for the amplifier module, whose final transistor will make or break the primary coil circuit. The output signals also control the full load enrichening circuit of the injection ECU and the LED knock indicator.

The Volvo B280F engine utilizes 2 knock sensors, one for each cylinder bank. They are located below the intake manifold in the center of the block. The knock sensors are a new type with a through bushing which makes them less sensitive to improper torque.

The knock sensors consist of piezo-electric transducers which produce a current within the frequency range which occurs when a cylinder knocks. The ECU will retard ignition timing by 3 degrees for the individual cylinder that developed knocking. When knocking stops the ECU will hold the retarded ignition timing for a number of revolutions, depending on engine speed.

PRELIMINARY TEST PROCEDURES

Ignition Secondary Checks and Coil Resistance Checks are basic system tests, required whenever ignition problems are suspected. See the TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section. Also check for hard codes which may be set in the computer. If any codes are set they must be checked and/or corrected prior to the following testing procedures.

Scheme 8

Scheme 9

Scheme 10

1. Check the ground connections from ignition ECU and power stage to inlet manifold ground to ensure proper connection. If ground connections are good, disconnect one spark plug wire from a spark plug. Attach a test spark plug to the disconnected spark plug wire, crank engine and monitor spark.
2. A strong Blue-White spark indicates an engine or fuel system malfunction. If no spark or a weak spark is present, reconnect spark plug wire to spark plug. Disconnect coil wire from distributor cap and install test spark plug. Crank engine and monitor spark. If no spark or weak spark is present, the coil or ignition system low tension circuit is defective.
3. If a strong Blue-White spark is present, check ignition rotor, distributor housing and spark plug wires. Replace components as necessary. If all the previous steps show no defective components, proceed to next step.
4. Remove air cleaner assembly. Ensure ignition is off and disconnect power stage connector. Remove connector dust cover. (Scheme 8) Attach multimeter negative (-) lead to ground and positive (+) lead to connector pin No. 4. Turn ignition on and note voltage reading. Voltage should be approximately 12 volts. (Scheme 8): Power Stage Location & Connector Identification
5. Leaving, multimeter attached, crank starter motor. Voltage should be approximately 12 volts. If voltage reading is too low, check battery and charging system. If voltage is not present, check Black wire from ignition ECU to ignition coil and power stage. Repair or replace as needed.
6. Check power stage ground resistance with multimeter attached between power stage connector pin No. 2 and ground. Resistance should be zero ohms. Check ignition coil resistance with multimeter attached between power stage connector pin No. 1 and No. 4. Resistance should be 0.6-1.0 ohm. If resistance is below 0.6 ohm, check wires for short circuit.
7. If wires are okay but resistance is still below 0.6 or above 1.0 ohm, attach multimeter between ignition coil terminal No. 1 and No. 15. (Scheme 9) If resistance is below 0.6 or above 1.0 ohm install a new ignition coil. If resistance is 0.6-1.0 ohm, check continuity of wires between ignition coil and power stage connector pin No. 1 and No. 4. Repair or replace as necessary. (Scheme 9): Ignition Coil Terminal Identification
8. Check shield wire (ground) between ignition ECU and power stage. (Scheme 8) Shield wire should be connected to power stage connector pin No. 3. Repair if necessary. Check that power stage receives ignition ECU signal by disconnecting wires from ignition coil terminal No. 1. Attach positive (+) lead of multimeter to power stage connector pin No. 5 and negative (-) lead to ground.
9. Crank starter motor and monitor voltage reading. Voltage should be 0-2 volts. If voltage is within specifications, install a new power stage and recheck circuit. If a very low voltage is present or voltage continuously fluctuates, check wiring between ignition ECU and crankshaft position sensor. Repair or replace as necessary.
10. Turn ignition off. Reconnect disconnected components. Ensure all connectors are secure and properly connected. With ignition off, remove panel from lower left dashboard and disconnect ignition ECU connector. Remove dust cover from connector. Visually inspect that all pin connection sleeves are at the same height. (Scheme 10): Checking RPM Position Sensor
11. Attach multimeter positive (+) lead to ignition ECU connector pin No. 6 and negative (-) lead to ground. Turn ignition on. Voltage should be approximately 12 volts. Check resistance of engine RPM position sensor by attaching multimeter leads between ignition ECU connector pin No. 10 and No. 23. (Scheme 10) Resistance should be 500-600 ohms. Check and ensure shield wire (ground) is connected to ECU connector pin No. 11.
12. Turn ignition off. If no defects are found after performing all previous steps, or if engine still malfunctions after repairs, install a new ignition ECU. Recheck system as necessary.

Sectional View of Hall Effect Distributor. Scheme 11

B280F With EZ115K System

1. Check timing with engine at normal operating temperature and idle speed. If timing is not within specifications perform «CIRCUIT CHECK»(/volvo/760/i-1982-1992/remont/ignition-system/#ignition-system-bosch-ezk-v6) in this article. If problem still exists, proceed to next step.
2. Check that wires from engine RPM/crankshaft sensor are correctly connected to the connector on left suspension tower. Check continuity of the wires. Repair or replace wire(s) as necessary. If problem still exists, proceed to next step.
3. Turn off ignition. Check that wires from cylinder one position sensor are correctly connected to the connector on left suspension tower. Check continuity of the wires. Repair or replace wire(s) as necessary.

EZ115K Connector & Pin Identification. Scheme 12

1. Install LED Tester using manufacturer's instructions. Turn ignition on. Diode light should be on. If light does not come on, check for an open circuit between test point connector wire and pin No. 3 of the ignition ECU. (Scheme 12) Repair and repeat test as necessary.
2. If light did come on, start engine and slowly increase the RPM. The light should go out when engine RPM is greater than 700 RPM. If light does not go out, there is a defect in the ignition ECU or a short circuit in the test point wiring. Repair and repeat testing.
3. After completing steps 1) and 2), test drive the vehicle while monitoring the LED Tester under conditions listed in the following steps. The LED Tester will flash any fault signals received from the ECU.
4. Drive vehicle with full load acceleration, then allow engine speed to drop to idle RPM. If one flash is counted, pre-ignition is indicated. Check for low fuel octane, high engine temperature, defective spark plugs or improper torque, air inlet leakage and excessive carbon build up.
5. Allow vehicle to maintain idle RPM and helper to monitor LED Tester. If 2 flashes are counted, an incorrect temperature sensor signal is indicated. Proceed to «CIRCUIT CHECKS»(/volvo/760/i-1982-1992/remont/ignition-system/#ignition-system-bosch-ezk-v6) in this article. If 3 flashes are counted, disregard as this is not used.
6. If 4 flashes are counted, incorrect knock sensor signal or defective knock detection circuit in ECU is indicated. Proceed to «CIRCUIT CHECKS»(/volvo/760/i-1982-1992/remont/ignition-system/#ignition-system-bosch-ezk-v6) in this article.
7. If 5 flashes are counted, incorrect load signal from fuel system ECU is indicated. Proceed to «CIRCUIT CHECKS»(/volvo/760/i-1982-1992/remont/ignition-system/#ignition-system-bosch-ezk-v6) in this article. If 6 flashes are counted, incorrect cylinder one position sensor signal is indicated. Proceed to «CIRCUIT CHECKS»(/volvo/760/i-1982-1992/remont/ignition-system/#ignition-system-bosch-ezk-v6) in this article.

Scheme 13

1. Turn ignition off. Remove panel from lower left of dashboard. Disconnect ECU connector from ECU. Remove cover from ECU connector. Visually inspect all pin connection sleeves to ensure all pins are at the same height. NOTE: When measuring resistance and voltage at connector, DO NOT probe into front of connector. Probe only through side of connector, just enough to make a good electrical contact. Pin identification is indicated on side of ECU connector.
2. Check temperature sensor circuit using a multimeter to measure resistance. Attach multimeter lead to pin No. 2 (Green wire) of the 8 pin "F" test connector, located on left suspension tower. Attach the other lead to a good ground. If resistance is not within specifications, repeat measurement at sensor(s) to determine if sensor wire(s) or sensor(s) is defective. See «TEMPERATURE SENSOR RESISTANCE»(/volvo/760/i-1982-1992/remont/ignition-system/#ignition-system-bosch-ezk-v6) table in this article. Repair or replace as necessary.
3. Check the knock sensor wire resistance with a multimeter. Disconnect the connector at fuel distribution rail. Attach a jumper wire between pin No. 1 and pin No. 2 of fuel distribution rail connector. Attach the multimeter leads between ignition ECU connector pins No. 12 and 13. (Scheme 13) Resistance should be zero ohms. Check resistance between ignition ECU connector pins No. 24 and 25. Resistance should be zero ohms. (Scheme 13): Ignition ECU & Fuel Distribution Rail Connector
4. If resistance is high, an open circuit is indicated. Remove jumper wire from fuel distribution rail connector and check continuity of each wire. Repair or replace as necessary. If wiring is okay but fault code still flashes, incorrect knock sensor signal is indicated.
5. Install a new ignition ECU and repeat test using LED Tester. If LED still flashes fault code, reinstall original ECU and install new knock sensor(s). Repeat test procedures to ensure problem is corrected.
6. Check fuel system ECU load signal with a multimeter set for voltage measurement reading. Attach multimeter leads between ignition ECU connector pin No. 8 and ground. Turn ignition on. Voltage should be approximately 11 volts. If voltage is low or zero, there is an open circuit between the fuel ECU and ignition ECU or a defective fuel ECU.
7. Check cylinder one position sensor using a multimeter set for ohms reading. Attach multimeter leads between ignition ECU connector pins No. 18 and 19. Resistance should be zero ohm. Check that shield wire (ground) is connected to connector pin No. 21. If not within specifications, position sensor is defective.
8. Check throttle switch resistance with multimeter. Attach multimeter leads between ignition ECU connector pin No. 7 and ground. Resistance should be zero ohm. Slowly depress accelerator to open throttle switch. Resistance should increase. If reading is incorrect, measure resistance at throttle switch to determine if wire is broken or if throttle switch is defective.
9. If necessary, check throttle switch adjustment. Open throttle valve slightly and listen for an audible click. The click indicates that throttle switch opens at the same time as the throttle valve. Adjust throttle switch if necessary.
10. Check engine RPM/crankshaft position sensor resistance with a multimeter. Connect multimeter leads between ignition ECU connector pins No. 10 and 23. Resistance should be 500-600 ohms. Check that shield wire (ground) is connected to connector pin No. 11. If not within specifications, replace RPM/crankshaft position sensor.
11. Check that test connector is not grounded using a multimeter. Connect multimeter leads between ignition ECU connector pin No. 13 and ground. Resistance should be infinity. If not within specifications, test connector is either damaged or grounded. The test connector is a one wire (Yellow with Red) connector located at the right front fender in engine compartment by the air cleaner assembly.
12. Connect multimeter leads between ignition ECU connector pin No. 20 and ground. Resistance should be zero ohm. If not within specifications, repair open circuit.
13. Turn ignition off and reconnect ignition ECU connector. Remove air cleaner assembly to gain access to power stage connector. Disconnect power stage connector and remove connector dust cover. Check ignition coil primary winding resistance with a multimeter.
14. Connect multimeter leads between power stage connector pin No. 1 and No. 4. Resistance should be 0.6-1.0 ohm. If resistance is below 0.6 ohm, check wires for short circuit. If wires are okay and resistance is still below 0.6 ohm or above 1.0 ohm, proceed to next step.
15. Connect multimeter leads between ignition coil terminals. If resistance is below 0.6 ohm or above 1.0 ohm install a new ignition coil and recheck resistance. If resistance is correct, check continuity of wires between ignition coil and connector pins No. 1 and 4. Repair or replace wire as necessary.
16. Attach multimeter leads between terminal No. 1 of ignition coil and coil tower. (Scheme 9) Resistance should be 6500-9000 ohms. If not within specifications, replace ignition coil.
17. Check power stage ground resistance with a multimeter. Attach multimeter leads between power stage connector pin No. 2 and ground. Resistance should be zero ohm. Check shield wire between ignition ECU and power stage. Shield wire should be connected to pin No. 3 of power stage connector.
18. Check for voltage at ignition coil and power stage with a multimeter. Connect multimeter negative (-) lead to ground. Connect multimeter positive (+) lead to power stage connector pin No. 4. Turn ignition on and note voltage reading. Voltage should be approximately 12 volts. Proceed to next step.
19. Crank starter motor and observe voltage reading. Voltage should be at least 10.5 volts. If voltage is too low, check battery and charging system. If there is no voltage, check wires between ignition ECU, ignition coil and power stage. Repair or replace as necessary.
20. Turn ignition off. If no defects were found in the previous steps and problems still exists, install a new ignition ECU and/or power stage. Reconnect disconnected components and recheck system.

Distributor Connection Identification. Scheme 14

Checking Distributor-to-Ignition ECU. Scheme 15

SPECIFICATIONS

TEMPERATURE SENSOR RESISTANCE

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• CIRCUIT CHECK