High Energy Ignition (HEI) System
1. Disconnect the cable from the negative terminal of the battery.
Examination
2. Check the ignition coil for opens and shorts to ground by performing the following three tests with an ohmmeter (see illustration).
7.2 To check the ignition coil, perform the following three tests using an ohmmeter: 1 - when setting the ohmmeter to measure high resistances, the device arrow should point to "infinity", 2 - when setting the ohmmeter to measure low resistances, the device arrow should point to a value close to zero, 3 - when setting the ohmmeter to measure high resistances, the device arrow should not point to "infinity". If the device readings differ from those given above, the coil should be replaced
3. Set the ohmmeter to the high resistance scale and connect the leads as shown in the illustration (see check N1 in illustration 7.2). The ohmmeter should show a very high resistance value or even "infinity". If the readings are different, replace the coil.
4. Set the ohmmeter to the low resistance scale and connect its terminals as shown in the illustration (see N₂ check in Illustration 7.2). The ohmmeter should show a very low resistance value, even zero. If other readings are present, replace the coil.
5. Set the ohmmeter to the high resistance scale and connect the leads as shown in the illustration (see check N3 in illustration 7.2). The ohmmeter should not show "infinity". If the measured resistance is "infinity", replace the coil.
Removal
6. Disconnect the high tension wire and both electrical terminals from the ignition coil.
7. Unscrew the nuts (see illustration), remove the ignition coil from the engine.
7.7. Ignition coil mounting bolt locations (shown by arrows) on a 3.1 l engine
Installation
8. Installation of the ignition coil is carried out in the reverse order.
Direct Ignition System (DIS)
Examination
9. First, refer to Section 6 and perform the ignition system checks described there.
10. Using an ohmmeter, measure the resistance of the secondary winding of each coil (see illustration). The nominal resistance values are given in the technical specifications given in this chapter.
7.10 Measure the resistance of the secondary winding of each ignition coil
11. Then measure the resistance of the primary winding of each ignition coil (see illustration). The nominal resistance values are given in the technical specifications given in this chapter.
7.11 Measure the resistance of the primary winding of each ignition coil
Replacement
12. Disconnect the cable from the negative terminal of the battery.
13. Disconnect all electrical contacts from the unit.
14. If the high-voltage wires are not numbered, number them and disconnect them from the coils (see illustration).
7.14. Each high-voltage wire has its own number, stamped on the top of the ignition coil
15. Loosen the bolts and remove the coils and ignition unit from the vehicle (see illustration).
7.15. Carefully remove the coils from the ignition unit
16. After unscrewing the bolts, disconnect the ignition coils from the block (see illustration 7.14).
17. Installation is carried out in reverse order.
18. When installing the ignition coils, ensure that their terminals are connected correctly.
[The text of the article was obtained from the website «CHEVYMAN»]