Ignition Coil and Ignition Power Transistor

Operation

When ignition power transistor unit A is switched ON by signals from the engine control module, primary current flows to ignition coil A. When ignition power transistor unit A is switched OFF, the primary current is interrupted, high Voltage is generated at secondary coil A, and the spark plug for the No.1 and No.4 cylinders sparks. When, however, ignition power transistor unit B is switched from ON to OFF, the spark plug for the No.2 and No.3 cylinders sparks.

When the engine control module switches OFF the power transistor inside the unit, battery Voltage is applied to the ignition power transistor unit, and the ignition power transistor unit is switched ON.

When the engine switches ON the ignition power transistor within the unit, however, the ignition power transistor unit is switched OFF.





Inspection








Harness Inspection

Ignition Coil





(1) Measurement of the primary coil resistance.
(2) Measure the resistance between connector terminals 3 and 2 (the coils at the No.1 and No.4 cylinder sides) of the ignition coil, and between terminals 3 and 1 (the coils at the No. 2 and No.3 cylinder sides).

Standard value: 0.77-0.95 Ohms

(3) Measurement of secondary coil resistance.





(4) Measure the resistance between the high-Voltage terminals for the No. 1 and No.4 cylinders, and between the high-Voltage terminals for the No.2 and No.3 cylinders.

Standard value: 10.3-13.9 K Ohms

Caution:Be sure, when measuring the resistance of the secondary coil, to disconnect the connector of the ignition coil.

Ignition Power Transistor

Note: An analog type circuit tester should be used

No. 1-No. 4 coil side





(1) Connect the negative (-) terminal of the 1.5V power supply to terminal 3 of the ignition power transistor; then check whether there is continuity between terminal 3 and terminal 8 when terminal 7 and the positive (+) terminal are connected and disconnected.





Note: Connect the negative (-) probe of the circuit tester to terminal 8.

No. 2-No. 4 coil side





(1) Connect the negative (-) terminal of the 1.5V power supply to terminal 3 of the ignition power transistor; then check whether there is continuity between terminal 1 and terminal 3 when terminal 2 and the positive (+) terminal are connected and disconnected.





Note: Connect the negative (-) probe of the circuit tester to terminal 1.

If the problem is still evident after checking as described above, replace the ignition power transistor.