Hey, my truck quit running suddenly. I found there was no spark coming thru and started to work backwards. Someone suggested the ignition module (two connector type)-I swapped it out, and it started right up, ran great. The next time I went to start it, same problem.
I checked for good grounds, loose connectors, checked resistance on the coil, and have found nothing. I even swapped the ignition module again, on the chance the replacement was just a dud (made in China). Still don't have a clue. Why would it run once and then quit again, after I swapped the module? Could it be unrelated to the module? Ignition switch maybe? Any suggestions are welcome.
I should probably mention that the 460 is a rebuild, and not the original motor. This rig started out in life as a diesel.

 

Welcome to the forum watt476!
(at first I thought it said watt 746... as in one horsepower)

You should check your ignition coil.
The factory DuraSpark II has a ballast resistor wire integral to the wiring harness.
The coil only 'sees' 12V while cranking the starter, and ~7V in the run position.
Too much voltage will cook the coil.
Who knows what was done when they converted from diesel?

The only other thing I can think of that would affect the reliable DSII system would be the pickup inside the distributor.
IIRC you should have 500-900 ohms across the orange and purple wires at the distributor plug.

 

ArdWrknTrk: thanks for a reply. And thanks for the welcome!
I'm not sure if the ballast is handled with a wire, or if it's handled at the switch. I've heard both, and yea, I don't know how the conversion was made. I had thought the wire would be obvious, but I can't find it. And both red and white wires from ignition module are soldered together. I checked resistance, primary and secondary, on the coil, and the numbers I got were consistent with spec. Lock cylinder on steering column was turning freely, without a key, and truck has been sitting in high moisture area for a while. I thought some corrosion might be causing problem. I just bought ignition switch and lock cylinder, and will swap them out tomorrow, and let you know. I will check resistance b/w orange and purple wires too. Thanks for the advice.

Jim from Washington

 

I can say for certain that in an '86, and my '87 the ballast resistor is a thick pink section of wire taped up in the harness itself.

The wires soldered together is very good, because the timing retard feature will not function.
Ideally the white wire should only have power while cranking.

Can you measure how much voltage you have going to the coil with the ignition in the run position?

 

I have 11.4 volts at battery terminal of coil with key in the run position. With 11.87 at battery (needs a charge). And I have no resistance b/w orange and purple wires on dist plug. If I'm reading you right, that means that the ballast resistor is bad (wherever it is-I still haven't found it), and that the pickup on the dist is bad. Does that sound right?

 

Jim, watt, the 85 system has the ballast resistor built into the main harness. It feeds the red/light green wire going to the coil. The white/light blue wire feeds the DSII module red wire. It is not powered when cranking. The module white wire is powered through the starter signal when cranking. The distributor pickup should have some resistance.

AllData says to check the ballast resistor by unplugging the module connectors the one with the red and white wires then the ignition coil.

With the ignition OFF measure the resistance from the battery (+) terminal of the ignition coil connector to the white/light blue wire on the harness connector.

Resistance should be 0.8-1.6 ohms, more or less, the resistance wire is bad.

For the pickup, you were measuring correctly, it should be 400-1000 ohms, again more or less, replace it. I don't know where you are, watt476, but I have a distributor I pulled out of my 86 when I converted to EFI that worked perfectly.

 

Bill,
The OP states in post #3 that this was originally a Diesel truck that has been swapped to 460/DSII.

That the red and white wires going to the DSII plug are soldered together where they are spliced into the truck.

 

Yeah, I saw that, Why the PO did that is a good question, Ford may have used a different harness on the diesel, on the gas trucks, even the EFI uses the same main harness, it's all plug in on the left side.

 

Guys, thanks for the information. I'll test again for the ballast resist like you suggest, and locate the wire. And swap out the stator assembly , since it has no resistance. I just had a look at it, and it is sort of flopping around in the distributor case. I don't see anywhere that it fastens to the case, but I don't see how it can move freely in there the way it is now. Anyway, I'll take care of this, and get back.

 

Here is a good tutorial for distributor disassembly.

This should help you get the pickup out and the new one installed.

Duraspark_distributor_recurve_instructions_index

 

Took me a while to get to it....
I swapped out the stator assy and she fired right up. There were some small welds where the pickup attaches to a ring that slides around the dist shaft-these welds failed for some reason, leaving the assy flopping around, and useless.
I never did find the ballast resistor, and since the red and white wires are spliced together, this must be other than stock configuration, if I'm understanding how this is supposed to work. When I have time, I'll keep digging-it's got me curious. Maybe ballast is handled at the coil?
Anyway, for now I'm happy she's running. And she's running better than before.

 

On pre-87 trucks with DSII the ballast resistor is in the harness feeding the coil and the bypass portion is also built into the harness. Since 85 and 86 trucks were transitioning from all carbureted to some EFI, the harnesses were built as an overlay for EFI and the six cyl. feedback carbs. The stuff on gas engines all plugged into the same connections for any of the 3 systems.

 

Glad you figured it out. When I had my 86 F250 I had kind of a similar deal & it was the distributor. On mine I used up 3 distributors in 14 years & 70,000 miles.

 

Thanks for the information guys. When I get more information about the configuration I'll pass it on.