Primary Circuit Test (Closed Bowl Distributor)
- Disconnect terminal "S" at starter relay to allow testing of ignition primary circuit without cranking motor. Ensure ignition is off. Push down on connector tab and disconnect harness connector from TFI module. Ensure TFI module connector is not corroded or swollen. Repair or replace connector as necessary.NOTE: If connector is damaged or has broken tabs due to misuse, replace connector. A loose or damaged connector may cause ignition signal faults during KOER operation.
- Use a straight pin or terminal spade from an old TFI module to probe connector. Avoid ground contact, between straight pin and ground, during testing. Using a DVOM, turn ignition on and measure voltage at following vehicle harness connector terminals of cowl mounted TFI module: See Figure.
Key On Engine Cranking (KOEC)
- No. 3 (Power/Run Circuit)
- No. 4 (Start Circuit)
Key On Engine Off (KOEO)
- No. 3 (Power/Run Circuit)
If approximate Battery Voltage (VBAT) is not present at these terminals, repair open circuits in wiring harness as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.
- If battery voltage is as specified, check module ground circuit. With TFI module disconnected and KOEO, measure voltage at terminal No. 6. If voltage is greater than .5 volt, ground circuit has high resistance or is open. Repair as necessary.
- Ensure ignition is off. Disconnect distributor connector. Turn ignition on. With DVOM set on DC voltage scale, connect positive (+) lead to terminal No. 8 (terminal No. 4 on 3.0L Aerostar and Ranger). Connect negative (-) lead to distributor or engine ground. See Fig 1.
- Cycle ignition switch between ON and START positions. Battery voltage should be present in both positions. If not, service or repair circuit as necessary. If okay, go to next step.
- Use a DVOM to check ignition ground circuits continuity. Measure resistance between distributor base and terminals No. 2 and No. 6 at distributor connector (terminal No. 3 on 3.0L Aerostar and Ranger). If resistance at each terminal is less than 3 ohms, circuit is okay. If resistance is 3 ohms or more, repair ground circuit as necessary. See Fig 2.