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1979 Ford Bronco F100-F350 Ignition System Wiring Diagram & Spark Test Guide
Reference · 1978-1979 BroncoAll 116 wiring diagrams
Ignition system wiring schematic (Ford Duraspark) showing ignition module, coil, distributor, starter relay and engine speed sensor with cranking spark-test procedure (white wire voltage within 1 volt).
Part of 1978-1979 Ford Bronco Wiring Diagrams
This page (page 11) from a 1979 Ford Bronco / F100-F350 truck electrical reference covers troubleshooting and wiring of the breakerless (DuraSpark-type) ignition and starting system. The left column gives step-by-step spark test procedures: tapping the distributor after removing a paper clip from the module, a cranking test holding a spark plug 1/4 inch from ground, measuring battery voltage through the white wire into the ignition module with a pin, and checking voltage at the coil BAT terminal to diagnose a malfunctioning module or bad feed wire. It refers readers to the 1979 Ford Car Shop Manual Section 29-02 for complete diagnosis. The wiring diagram shows the ignition switch (ACCY/RUN/START/OFF), neutral start switch (automatic transmission), starter relay, starter motor, breakerless ignition module, radio noise capacitor (optional), ignition coil, and breakerless distributor, with wire color codes (y, w, r/bl, r/gr, br, bk, bk/gr, p, o, dg, dg/y, o/y, p/bl) and a 1.05-1.15 ohm resistance wire noted. Bronco vs. F100-350 wiring differences are indicated. A legend table lists component locations (ignition module on LH fender apron, starter relay on RH fender apron, etc.) and connector descriptions for C220, C321, C322, C323, C1015 and splice S302.
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Frequently asked questions
- Where is the ignition module located on a 1979 Ford Bronco/F-Series truck?
- According to the component location table, the ignition module is on the LH fender apron; the starter relay is on the RH fender apron, the ignition coil is mounted on the engine, and the magnetic pickup coil is in the distributor.
- What is the resistance value of the ignition resistance wire?
- The diagram notes a resistance wire of 1.05 to 1.15 ohms feeding the ignition coil circuit.
- How do I perform the cranking spark test?
- Hold a spark plug in the coil wire 1/4 inch from a ground such as the engine block and crank the car. A spark indicates the problem is not in the ignition system. If there is no spark, measure battery voltage while cranking and compare it to the voltage through the white wire into the ignition module (pierce it with a small straight pin); they should be within 1 volt of each other.
- What does equal voltage at the coil BAT terminal indicate?
- If the voltage on the coil's BAT terminal while cranking equals battery voltage but there is no spark, a malfunctioning module is indicated. If the voltages are not equal, repair the wire feeding the coil's BAT terminal.
- What are connectors C321, C322 and C323 in this ignition system?
- C321 is a round, brown, 2-terminal connector at the ignition module; C322 is a round, brown, 3-terminal connector on the engine at the distributor; C323 is a round, brown, 4-terminal connector at the engine module. C220 is a square, grey, 4-terminal connector in the engine compartment near the dash, and C1015 is a square, grey, 4-terminal connector on the transmission housing.
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