'70 Duraspark conversion - need resistor wire?

[sargentrs]

That's interesting. Turning the key off should have cut all power to both the relay, the solenoid and the coil. Shouldn't have been any power for the distributor to even spark. Did you leave the original brown wire still connected to the "I" terminal? I did and it didn't affect anything. The only real difference between our wiring is that I came off the battery terminal straight to the relay and you went off the solenoid to the relay. That shouldn't have mattered. The other difference is I splice a "Y" connection further back at the firewall and one leg to the "I" terminal on the solenoid and the other leg to the coil. That was so I could split them back at the firewall and route the solenoid wire along the with the original harness (at the inner fender) and the coil wire ran alongside the valve cover and intake. Effectively, you're running in series where I'm running in parallel, although the same wires are connected together just farther back in the circuit. Still should have been the same effect.

I reviewed 3-4 different Duraspark wiring diagrams and all were different although none used a relay and all started back at the ignition switch. The Mustang crowd seemed to consistently connect to the "I" terminal on the solenoid but the Jeep crowd disconnected everything from the "I" terminal leaving it empty. There was one post where a guy experienced the same issue as you due to a sticking solenoid. He said it was random and when it wouldn't die, he'd just tap on the top of the solenoid with a hammer handle and it would quit.

Don't rule out another bad solenoid, I've installed 3 in a row before getting a good one. Also could be an issue with your ignition switch. The "ign switch wire" in your sketch, going to the #86 terminal, did you come off the 3 prong plug with the oil/water temp senders on it or did you come straight form the ignition switch? Regardless, if it's working without the "I" terminal connected, run with it! If it works, it's fixed

[redstone65]

Did you leave the original brown wire still connected to the "I" terminal?

Yes, I left it connected.

The "ign switch wire" in your sketch, going to the #86 terminal, did you come off the 3 prong plug with the oil/water temp senders on it or did you come straight from the ignition switch?

Yes, I came off of the 3 prong group with the oil/water temp senders.

He said it was random and when it wouldn't die, he'd just tap on the top of the solenoid with a hammer handle and it would quit.

I'm going to do some more experimenting tonight after work. I really want to know what the cause is. My only guess at this point is that something is causing enough feedback into the circuit to keep the relay closed, but not enough to trigger it initially. If the solenoid internal schematic in this diagram:



...is accurate, then the output from the relay feeding into the "I" terminal wouldn't be doing anything. And, in fact, could cause some harm to the starter motor if it keeps it engaged. Not sure if 30 amps is enough for that. I did notice last night when I bumped it over a few times during testing that the starter was struggling to engage sometimes. The night that it cranked and wouldn't turn off my son kept saying he heard a metal-on-metal sound. I didn't hear it, but he swore he did. Could have been the starter stuck engaged while it was running.

Regardless, if it's working without the "I" terminal connected, run with it! If it works, it's fixed.

Well, I didn't actually attempt to crank it last night. I just did various configuration tests with the multimeter. I had to put a muffler on last night too, since that thing is LOUD with just a straight pipe. I don't want to tick the neighbors off. Today will be the real crank test and I'll let you know.

[The Bandit]

How do you have the The duraspark ignition module itself mounted? is it grounded well?

[sargentrs]

Officially, the module is grounded through the black wire to the distributor and the circuitry in the module is not in contact anywhere in the housing itself. When the factory started building vehicles with plastic/fiberglass inner fenders they still mounted the module there. With that said, I'll still never install one without a separate ground wire to a metal fender/frame part.

[redstone65]

How do you have the The duraspark ignition module itself mounted? is it grounded well?

No, the housing isn't grounded yet, but that's the plan once I make the wiring permanent.

What I did last night:

- Traced the brown "I" wire and it comes out in the same group with the oil/water temp senders and the coil wire. It was just sitting there on top of the manifold. So, brown wire definitely not needed.

- Checked continuity between the "I" terminal on the solenoid and the starter wire output post with the battery disconnected. There was no continuity, so the "I" terminal connectivity must ride on the plate and not be permanently connected to the output post. That's good.

- Disconnected the red wire that was feeding back to the "I" terminal on the solenoid since it's clearly not needed and fired the engine up. It ran fine, and then I turned the key off and it stopped! Woo!

So, connecting the Duraspark circuit back to the "I" terminal doesn't do anything useful, electrically speaking.

[sargentrs]

So, connecting the Duraspark circuit back to the "I" terminal doesn't do anything useful, electrically speaking.

Scientically proven! Good to know. I'll eliminate that from future installations.

[redstone65]

Yep. Straight up car scientists.

I posted a little more detailed info over here for posterity.

I also figured out this little mystery too:

I also noticed last night that both tail lights (headlights are off) stay lit all the time when the battery is connected

It was just the brake light pedal switch hanging underneath the dashboard. I re-mounted it properly and no more always-on tail lights. That was a head fake. .

[dolinick]

I posted in the wrong area about my 1968 F500 300 inline six that I plan on converting to Duraspark II.

My distributor is bad so I decided to "steal" the distributor out of another 300 inline six that I believe
is a 1977-79 and "steal" the ignition module out of my 1983 F100 which also had a 300 inline six.

I can also get the coil and plug wires from the donor engine.

I think all I need is the relay and maybe some ring terminals to do it right.

My truck is stranded so i hope to get it running good enough to drive it home 15 miles.

[dolinick]

I did it! Today I tried a couple short test drives even though
the truck was running very poorly and was doing a U-turn when it
hit me like a ton of bricks; I had wired the spark plugs in reverse
order! I wired them counterclockwise instead of clockwise. I pulled over
on the side of the road and changed them. 153624 instead of 142635.
Only two cylinders were correct, the 1 and the 6. It started and ran
smooth as buttah!

Actually it has that little rough idle just like it did before I changed the entire
ignition system and four of the spark plugs and the spark plug wires and coil.
So I was thinking I need to check the spark plug gaps maybe and maybe get a
new set of wires but also adjust the valves! I think I remember watching a video
on how to adjust the valves on a 4.9L inline six. It should be pretty easy.
This 1968 F500 only has 77777 miles on it. It has a few moar than that but it rolled
over 77777 last week on my way home from work which is 16 miles.

I have the red and white wires connected to the original wire that went to the coil from
the ignition switch and the starter relay now. I don't know if I need the relay to bypass
the ballast resistor wire but it's not bypassed for now.

Thank You.