I have a 1966 F100 that has a 1975 6cyl engine. When I got it the engine has the old distributor, points, etc., I assume from the original. I have replaced it with a Duraspark ignition module, new dist, and coil. However, it still has the old ignition switch, the one with the pink resistor wire that runs from the switch under the dash. The wiring diagrams I've seen for this engine seem to show the resistor in a different place, under the hood on the engine side of the firewall, and the red wire from the ign module tyiing in between this resistor and the igtnition switch. Can I retain the original ignition switch with the pink resistor wire, and if so where would I tie the red wire from the module into it?

 

This should help.

 

Thanks, great diagram and I appreciate it. This module is different from mine as mine has the green insulator where the wires come out, and the two-wire set on mine are red and white instead of blue and red-blue. Any, I've tried the set-up in your diagram (bearing in mind the different coloured wires) and still nothing. I've tried a new module and still no spark. When I check with a light, there is power to the Batt side of the coil when I turn the key on. Good sign. But when I check the Tach side of the coil (with the other test lead on the Pos battery post), the light will not flash when the engine cranks (as it think it should accoring to the test instructions I have). My understanding is that this suggests the module is not sending power to the coil. I'm stumped.

 

Actually what I meant to say was the test light connected to the TACH side of coil and an engine ground. The light stays on and does not flash with the engine cranking over. I understand this indicates a faulty module. Anyone know for sure or have any advice?

 

If the light stays ON and does not BLINK, then the module is not switching the coil, because of the following:

1. Bad module.
2. No power to module.
3. Bad pickup module in the distributor.

On your new module, the RED wire is hot-in-RUN, and the WHITE wire is hot-in-START. You can retain the old ignition switch and resistor wire, which is used to power the coil in RUN. The coil gets powered by the full battery voltage in START, bypassing the resistor wire. This scheme is shown in the diagram and would have been implemented in your original points setup as well.

Hot-in-RUN for the module is easy to obtain, but hot-in-START is not as straightforward. Many circuits are hot-in-RUN, but very few are hot-in-START only that aren't also hot-at-all-times. In fact, there are only two: power to the starter solenoid, and power to the start-bypass circuit to the coil. How you can implement this setup depends on how many START (S) outputs your ignition switch has (1 or 2). A dual-post solenoid (with 'S' and 'I' terminals) can be used to provide an extra hot-in-START signal; this is most often used for the start-bypass circuit for the coil. The diagram shows this; the diagram also shows hot-in-START to the module tied to the same signal that powers the relay coil of the starter solenoid.

 

That's very useful. Thanks. I didn't realize a bad pick-up coil in the distributor could be the culprit. It might be worth changing that before driving myself more crazy with the modules.

 

D7AZ-12250-A .. Resistor Wire-Ignition Coil (Motorcraft DY-213).

49" long / 1.30-1.40 ohms resistance / color coded red with green stripes / #16 gauge wire.

1974/86: Use w/DuraSpark Electronic Ignition.
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D4PZ-12A112-A .. Stator aka magnetic pickup coil (Motorcraft DU-1A).

Fits: 1974/79 V8 Passenger Cars (except 1979 LTD/Merc Marquis 351W w/EEC), F100/350's, Bronco's & Econolines.

DuraSpark introduced 1974, but not all vehicles had it until 1976.

 

Your pickup module in distributor should read 400-800 ohms between orange and purple, either one to ground 70K ohms or more.

 

OK, I have my multi-meter and am ready to test the resistance in the pick-up coil. You say to check it orange to green wire under the cap, and both orange and green to ground. Those wires go into a black clip-type thing that seems to pug into that magnetic unit. So, do I unplug the wires from the unit under there, or what do I do to get the tester leads where I need them?

 

The distributor just unplugs from the harness about 8" away and you can read the pins. That would be 9,10, and 11 on the diagram I posted above.

 

Thanks again. I did that, placing the tester across purple and orange I got about 2500 ohms, and from purple to ground and from orange to ground I got nothing.

 

The > 70 k-ohm measurement between the PURPLE or ORANGE wires and ground is simply to make sure that either side of the pickup coil doesn't have a short to ground. If your meter reports nothing for either of those checks, then that means it's reporting an open-circuit, which is by definition greater than 70 k-ohm. So that's fine.

For the 2500 ohm reading, was this on the distributor-side of the connector? Meaning the wires coming from the distributor, not the truck harness? If so, and you're confident in the measurement, then that would indicate the pickup coil is bad. It's important that the meter gets a good solid connection to the terminals inside the connector. And again, it's important you're looking at the resistance of the pickup coil in the distributor, and not the resistance looking into the harness.

 

The 2500 reading was from the pin for the orange wire to the pin for the purple wire, on the harness that connects directly to the distributor (the short harness with the male pins that plugs into the harness coming from the module).

 

Here is a complete DSII test procedure for anyone interested.